I just returned from a 200 mile trip to the river (400 total pulling miles) and must say that I am very disappointed in my dmax. Pulled a 26' weekend warrior at approximately 8000 pounds. Conditions were extremely hot- ambient temp at 110F most of trip. Very often, the engine fan clutch kicked in and sucked all the power from my truck. The engine temp held steady at about 200f and the trans maintained 200f (once it reached approx 210 but only for a short while). The oil pressure hung around 40psi most of the trip- is that normal? Mileage according to the dic was 10.3mpg- terrible. I am a conservative driver and did not push the truck- maintained 55mph on the freeways. I did not hit the on-ramps at full throttle- just tried to accelerate normally. When that fan was on- the truck is guttless, when it is off it is pretty strong. What should I do? I cant believe that my 3/4 ton diesel $45K truck struggled with this moderate load- should I have stayed with my 1/2 Yukon with a 5.3L gas? I want to complain to the dealer but I'm not really sure how to approach the issue. My truck is new (2005) and now has 1300 miles. I thought that buying a diesel would net better mileage (11-13 towing) and give me more command of the trailer. Instead, I'm worried that it won't be able to tow my toyhauler when it actually is loaded with quads! In addition, when that fan kicked in, it is very loud and causes an annoying whistle inside the cab that sounds similar to a rubbing disc brake. Further, how can I tell if the turbo is doing its job correctly? What about changing the stock fan clutch and installing electric fans to eliminate the power drain and noise?

Your truck isn't broken in yet. Wait until you hit about 10K miles and it will come alive. I've pulled my friends 6300lb toyhauler up 6 and7% grades with the AC on and was able to keep 70mph. That was with no power adders. At least you got one thing in your favor at this point and that is it didn't overheat.

I have to agree with the 10k-15k breakin period. I never believed it till my 2004.5 lly hit 15k - MAN it was like a different truck. I was going to trade it for a 05 DRW and didn't want to give it up it was running so nice and had a new level of power than prior to 15k ( where that came from I don't know)
Got the 05 and am putting on my 15k as soon as I can.

Pulled a 26' weekend warrior at approximately 8000 pounds.

Did you pull this trailer with your Yukon ?

The oil pressure hung around 40psi most of the trip- is that normal?

Yes.

Mileage according to the dic was 10.3mpg- terrible.

What was your Towing Milage with the Yukon ?

I cant believe that my 3/4 ton diesel $45K truck truggled with this moderate load- should I have stayed with my 1/2 Yukon with a 5.3L gas?

Are you saying the 5.3L gas pulled better than the 6.6L DMax ?

My truck is new (2005) and now has 1300 miles.

Let it break-in.

I thought that buying a diesel would net better mileage (11-13 towing) and give me more command of the trailer. Instead, I'm worried that it won't be able to tow my toyhauler when it actually is loaded with quads!

Spend a little time Reading this Forum. Learn a little about these TRUCKS.

In addition, when that fan kicked in, it is very loud...

The Fan does what a Fan does.

Hang-in there.

Idahofox

Sounds like something is wrong. I have pulled a 10,200lb boat from almost day one with my truck, and it pull like a freight train up and down hills. You shouldn't even know it's back there....... Maybe your turbo isn't spooling up or something?

Superdiesel, you beat me to the punch. Just got back from a camping trip to lake isabella. My truck has a little over 5k on it and pulling 8k also. According to the DIC, we got 9.4mpg. Hand calculated, it was 9.2. This is ridiculus. It wasn't even that hot outside, maybe high 80's, and the damn fan kept coming on. And we hadn't even reached the big hill yet. Once we hit the big hill, maybe 6%, the fan never shut off, and the engine temp hit the line just before the middle line between 210 & 260, I figure 235 or so. The trans never got above 200, which was great. This shouldn't even be a workout for this truck. I too had a 1/2 ton, 5.3, Z-71, and going up the grapevine heading south, which is I would say a 6% grade, and with that truck I could maintain 50-55 in 2nd gear and the temps would jump a little over 210, but not for long. That was even when it was hotter, closer to 100 outside. And the fan didn't even kick on. I kept telling my wife we needed the diesel if we wanted to go camping more often, and farther away. After this trip, she is pissed that we bought this truck because I am pissed that it runs too hot and doesn't seem to have the power that everyone is talking about. Granted, I was in 4th gear as opposed to 2nd, but with the fan on, the power seems to disappear. It's no fun having to crank the stereo just to drown out the noise. I know everyone is going to say wait until the truck has at least 10k on it, but I shouldn't have to wait that long just to go camping. I have read all the posts regarding overheating on the 04.5's & 05's, so is that why the fan keeps kicking on? Even driving on flat roads going to lake isabella, the windy part that runs along the river, the fan kept coming on. I was doing around 35 -40 and the outside temp dropped to 80 according to temp gauge on the truck. This just isn't fun. Somebody please set me at ease. Or do I have a problem and need to take it in to have it checked? And on a side note, after we dropped off the trailer, I barely beat a furd f-150 that had 35's on it. We were basically side by side until about 50. I would of figured it wouldn't even be a race. Ok, whining is over. Jerry.

well i just got back from the river also temps had to have been 115-120 all the way back as you can see i pull a 30ft weekend warrior id say its about #9500 not loaded with the toys and yanked it all the way up to lake havasue no prob. you are right about the fan it robbs some power mine stayyed on for long periods at a time but still towing it is no prob. maybe it is the break in i noteced a big change around 10500 miles i now have 11500.

p.s. i also tow this same trailer to glamis or dumont fully loaded four quads in the trailer one quad in my bed and full of water it pulls no prob id say total wight is about 12500-13000 i wouldnt worry just step on it you got a great setup.

My truck only has a round 2,500 miles and I have only pulled a 3k pound boat. To compare I have pulled the same load with a 5.3 Z-71 w/ 4.10 gears as well as a 4.7 Tundra. I have to say there is no comparison. Any puff of wind or a tiny overpass and the little gassers will down shift. With the diesel the boat was hardly noticable.

As far as an empty drag race, I don't know. I wouldn't bet on my stock diesel beating either a Z-71 or tundra. Too much extra weight. I wouldn't say it isn't fun to drive though, pretty dang peppy if you ask me.

Just my .02 but I vote for a possible problem, i.e. fuel, fuel filter, ali spin on, etc.

My truck has 3,500 miles on it. I just got back from towing a 6200# trailer to Morro Bay and back including Pacheco pass. I got 15 mpg and ran with the cruise control at 65. The passes were also at 65, but not on cruise. Either you guys got lemons, with some problems the dealers should address or you just like to complain.

Stock Duramax would smoke a Z-71 or a Tundra. Read the "Kill Stories Forum"! I tow a 10,000#+ trailer in all ranges of temperature on 37" tires. I'm very pleased with it's performance, however I too hate the fan! Give it time to break in.

I'm going to contact the dealer and tell them that I don't feel that my truck is acting right- I'm not really sure just what to tell them though. In response to Idahofox, Yes, I've pulled this trailer loaded almost identically with relative success. Pulling up and over windy point outside of Palm Springs was a second gear challenge for it but the fan never kicked in like my "superdiesel". I expect the Yukon to get poor mileage (9mgp) but thought the diesel would fare better. I cant say the Yukon 5.3 gas pulled better than the diesel, but I am saying that the diesel does not pull better when the damned fan is kicked on! What happens to a diesel after it is 'broke in' around 10K miles. The real improvement that my new truck has over the Yukon are the stiffer springs and longer wheelbase. (3/4 ton crew cab long bed compared to a 1/2 ton short and cute Yukon) The truck was minimally affected by wind and passing trucks compared to the white knuckle ride in the Yukon! If I could find a way to eliminate the cooling fan, the diesel would be satisfactory. Further, I would expect the trailering mileage to drastically improve with the elimination of the fan. Can you replace the engine fan with an electric fan?

superdiesel - as a point of reference, going from 9mpg to 10.3 mpg is about a
15 percent gain in milage. What were you expecting?

Jim

Stock Duramax would smoke a Z-71 or a Tundra. Read the "Kill Stories Forum"!

Interesting......

Seat of the pants it is difficult to tell. I'm pretty sure both are in the 16 to upper 15 sec range in the 1/4, could be wrong though.

Superdiesel, I doubt there is an electric fan produced that will even come close to pulling enough air. I have never seen one at least.

You need a towing tune IMO.

Understand that the CC/LB 4x4 Dmax weighs about 7000lb empty. Yukon is about 2000lb less.

On the hills through Palm Springs there is a very heavy wind, and wind is the #1 enemy of towing performance with tall trailers. With a 13,000lb combined weight E-350 + towbox, I would routinely get 7mpg going into the wind, and 9mpg with no wind.

I honestly think a good portion of the "my old truck got better mileage" threads we see here are based on "apples and oranges" comparisons. Often they take the best mileage their old truck ever got, and compare it to towing in poor conditions with their new truck. If your Yukon got 9.x MPG with a 8000lb high-profile trailer behind it in the summer at high altitude going into wind, it was doing pretty good. I will admit the 2nd gear thing puzzles me. How fast can you go in 2nd? 50?

Another thing I'd try would be going 65-70 towing. This is where the Dmax is into it's powerband. Sadly California is one of the very few states that thinks it's safer to mix cars going 80mph with trucks going 55mph on the same road. If you must stay down to 55-60, use the OD lockout.

My truck got it's first 8,000+ load at 1,000miles. It pulled like a bitzh!
Now, this is Florida though... basically flat, but hot, and never a downhill to coast on....
The truck is now on 285/75-16s and I run a Predator programmer on the 60hp setting. I used it to correct the speedo..now it's 3 mph slower than my handheld GPS.
I don't know if reprogramming tire size has an effect on the odometer...
Truck has500miles on it now. I filled it today.
212.7 miles on the trip odo, 17.35 gallons in. That's 12.25 mpgs...EMPTY, NO LOAD!
Yes, I expected more. Dash computer is BS saying I got 16.5.
16.5 is what I expect, not 12.25.

SO, we'll see on the next tank...:o:

Oh, BTW- My truck hauls AZZ! I can light the 285s easily. I smoked a Nissan 350 Z the other day...easily. Never had a problem beating a Ford...Except for that new Mustang GT...;)

I too was dissappointed with my 05 dmax on its first pull with 1300 miles. My previous truck was a 2003 chevy 6.0 crewcab. With the 6.0 pulling 9000 lbs to pinecrest CA I would get 8 mpg round trip and pull the grade at 45 in second gear 4400 rpms. With the dmax I was expecting 60 up the grade and 10-12 mpg. The first part of the trip I was getting 10 mpg then I hit the grade and and the fastest I could go was 50 mph floored, fan was making more noise than my 6.0 tached at 4500 rpms and by the time I got to the campground my mpg was only 6.6. Needless to say my camping trip was not good after the dissapointment of the dmax. My round trip gas mileage was 8.5. Hopefully someone on this fourm will have the answer to why our trucks are not performing like thiers. I would hate to go through the lemon buyback process again.

To all who miss their gassers, I'm offering 10k cash for your new truck and I'll help you find a gasser to replace it. This offer limited to the first 3 to respond.

I wonder what the whole "it gets better after 10 to 15 thousand miles" thing is all about. Does the engine loosen up or is it a limiting factor put into the computer's basic program? And if it is the computer then do the power programers defeat this?

Just seems strange to me I have to use up half of the truck's warranty (not the engine's) before it starts performing as expected.

My dad has a 2002 and the fan kicks on all the time, I have a 2003 and mine very rarely kicks on even before the upgrades. He just got a 2005 and the fan doesn't kick on very often on it. The lly seems to pull well compared to the other two when they were stock. The 2005 is running strong and getting better mpg than the older ones we have and it has less than 1000 miles on it. If it gets stronger at 10000 miles I will be very impressed with the power. We regularly pull 20 to 30 thousand pound loads.

I run the crap out of my vehicles, all of them. I street raced and track raced cars for 15 years.

As it sits now my truck can easily trash a Tundra or any gasser Chevy truck.

Return it to stock and they both beat me. My advice is don't bet money on a stock dmax outrunning those. It won't happen.

.

I too was a 6.0 gasser before switching over to the D/A combo. I daily tow a Caterpillar Skidsteer approx. 8000 lbs and/or a Mini Excavator with a weight of 6500 lbs to the job site. My previous truck was an 03 2500 HD EC SB 6.0 4x4, and it would pull all day long. Not the best mileage but lets face it.....it's not an economy car it's a 3/4 ton truck. I liked the power but everyone told me how much better the diesel would be. Well after two and half weeks and 2500 miles on my new 05 2500HD CC LB D/A........I'm not that impressed. Not to mention the extra in payment, fuel, and maintenance.
That Flippn' fan kicks in an that damn hampster inside the engine quits running. I would hate to see if I was pulling my old 29 ft fifth wheel. Where is the power???
So if diesels are so great......where the hell is the performance....I don't want to wait until the majical 10k miles comes around to pull this Cat faster than the Chevette next to me.

Superdiesel Have your dealer check your charge air cooler for leaks. They should have the hose fittings and gauges to do it. Tim

I have been towing our camper (approx. 6500#) alot this summer and I will say this truck (I have 05 cc sb with 7500 mi.) tows like crazy. I towed for 5 years with a 5.3l 1/2 ton and there is NO comparison. My brother has a very similar camper that he tows with a 6.0l and I can tell you there is know comparison between my truck and his 6.0. Plus my mileage is 12 compared to his 8 on the exact same trip going the exact same speed. I set the cruise at 70 and let er rip and the truck has never downshifted on any hill that I've been on in the state of Wisconsin..... life is good. By the way I get better mileage towing than the 6.0 gets empty. And yes all mileage calcs are hand calculated.....

Just more incentive to never sell my truck.

I run the crap out of my vehicles, all of them. I street raced and track raced cars for 15 years.

As it sits now my truck can easily trash a Tundra or any gasser Chevy truck.

Return it to stock and they both beat me. My advice is don't bet money on a stock dmax outrunning those. It won't happen.

.

Glad I got a good one then. I raced many gasser trucks stock for stock and none were anywhere close to mine. Same size tires and in a couple cases exact same truck except they had the 6.0 or 8.1 motor... They did better than the 5.3 did, especially the 8.1, but were still several lengths behind when we limited out.

04.5 CCSB D/A LT

I wish I could add some good news but I kept waiting for better performance and mileage but it has not come. I now have 26,000 and I'm as disappointed as ever.

It frustrates me to no end to use more fuel and be slower than my buddies older D'maxes. I will use more fuel empty than they do with a 4k trailer. Same road same trip. I cannot match the mileage or empty performance of my bro's 02' Denali.

I am a die hard GM guy but this thing is slow when you work it (as temps rise) and my boat only scales at 4,300 lbs. Dealer cant find anything wrong and I hate to dump any money into a truck that deep down seems like a lemon.

I hope the sharp guys on around here figure this out!!

To GM's defense I think all the Common Rail trucks are inconsistent on mileage and some performance.

I think some of you guys are expecting your towing truck and trailer to run like a vette on the dragstrip... it's not going to happen. But I will comment that my 04' LB7 pulling a combined weight of 17500 at 70MPH is easy work and temps never climbed over 210... I averaged (hand calculated) 14 MPG. This truck pulls effortlessly compared to other trucks I have used. The biggest problem I see right now is some of you are looking for a miracle 20+ MPG towing. When I read posts like this, it makes me wonder about all the variables involved in MPG, how it was calculated, how was truck refueled etc...

Dan

To all who miss their gassers, I'm offering 10k cash for your new truck and I'll help you find a gasser to replace it. This offer limited to the first 3 to respond.

:exactly: I'm with him, you guy's sure complain alot about an awsome truck.

Let me clear up a few issues with my problem- yes, I'm disappointed with the mileage so far...but it is slightly better than my previous tow vehicle. (At least it did not go backwards.) My primary issue with my truck is related to the fan clutch. When the fan is on, the power is gone! Perhaps I have been naive to the diesel engine and had unrealistic expectations, but after spending HOURS reading this site prior to my purchase, I was under the impression that most were extremely satisfied with the dmax. In any conversation comparing my Yukon to a Dmax truck, no one would expect the Yukon to even compete with the dmax when towing... I will say that the truck is good when the fan is not running, but the fan seems to run most of the time! Anyway, I took the truck to the dealer and asked them to check the fan clutch operation and also look at the turbo due to a funky, inconsistent whining heard when the fan is working. I expect that they will simply test drive it, check for error codes (finding none), and tell me that all is well. I really hope that the 10K break-in happens for me as it apparently has for others.

Here comes a dose of blasphemy:

There is no such thing as "magic diesel horsepower". A stock Dmax is a 310HP engine. At peak HP, a 6.0 is going to pull just about as hard. An 8.1 will actually pull harder. The fuel consumption at any HP point is going to be better with the diesel though. It's more efficient and the fuel has more energy per gallon than gasoline.

However... In 5 minutes you can turn your 310HP Duramax into a 400HP Duramax, and it will wipe out any stock gasser in a towing contest. Oddly enough, the fuel mileage doesn't go down. It might even go up.

It wasn't long ago that diesel pickups put out about 215HP on a good day. You bought them because they got better mileage towing than a gas engine, but you certainly couldn't keep up with a V-8 gas engine. Today that has changed. Stock for stock, the diesel will be right there with the gas motors, and with a simple tune, exceed the power of any V-8 gas engine built.

If you bought a diesel pickup today and expected it to stomp all gas motors without tuning, you had too high of expectations. In particular, GM has developed some very fuel efficient and powerful LS1-based small blocks that are best gas truck engines in history when you look at all their attributes.

But a "tuned" turbo diesel is a force to reckoned with.

First, let me say that I think the 10,000 mile break in isn't going to be as dramatic as some would lead you to believe. If you are having that much trouble pulling that light of a load, then something is wrong. Your dealer will never find the problem until whatever is wrong goes from bad to broken. However, you should go to the three closest dealers and ask to speak to their diesel expert. You might get lucky and find one that just fixed the problem for another guy. Remember, not every dmax owner is a member here so there are guys with problems that never get on this website.

Lastly, let me say this. Stock for stock, my Tundra will whip the asbestos of any stock dmax. However, put a tune on a dmax and set it to even the lowest setting and I'll be breathing diesel for the rest of the day. I know, I've owned both trucks!

If I thought that my truck was as down on power as many of you think yours are I'd be taking it to a Dyno. That's the only way you know for sure if something is wrong. Plus you have amunition to go back to the dealer with if you are really down on power.

All you have to do is thumb through road test summaries of Car and Driver or Motor Trend.

I think the best 0-60 I have ever seen for Dmax listed was 8.8 with quarter miles in the 16's

I don't recall seeing it listed as faster than any Chevy gas truck in the same lists, or the Ford PSD for that matter.

The Tundra's run 0-60 in the 7.x range and 15's in the quarter. Stock for stock you ain't beating them. In racing 1 second is forever, a guy 1 second faster than you in drag racing beats you EVERY time.

.

I am with superdiesel in the fact that the fan seems like it comes on too much, especially pulling a load as light as 8k. If these things can pull 16k like the book says, then why at 8k does it seem to work so hard seeing as the fan comes on so much. I would be curious as to how my truck would pull 15k up a hill. Would I be doing 35 or 40 with the fan on the whole way up, and in 3rd gear? Don't get me wrong, 4th gear is much better than 2nd gear in my 1/2 ton, and maybe I AM expecting too much from this truck, but for 46k and the extra 5k+ for the diesel motor, I would think it would make a pretty big difference. Maybe there really is a problem with some of these trucks as far as heating issues are concerned. And maybe the trucks that don't have heating issues don't have the fan come on much at all. Or maybe I am climbing a steeper hill than I thought. I am not trying to complain here. Believe me when I say that I would much rather not to have to post one negative thread here. Jerry.

I would like to install an 8" Fabtect lift. How is the ride, did you have to swap gearsand what about the front axle boots? I just bought an 05 4x4 CC and love it. Any advise would be very helpful.

Your truck isn't broken in yet. Wait until you hit about 10K miles and it will come alive. I've pulled my friends 6300lb toyhauler up 6 and7% grades with the AC on and was able to keep 70mph. That was with no power adders. At least you got one thing in your favor at this point and that is it didn't overheat.

No way it's breakin. New trucks should be able to work at 100% right off the lot with minimal reduction in power level due to engine newness. They are designed to do so.

No way it's breakin. New trucks should be able to work at 100% right off the lot with minimal reduction in power level due to engine newness. They are designed to do so.

The key word here is should. I'm not saying they shouldn't be able to. It just seems to me that GM tunes them back a bit until they reach around 10K miles. I could be wrong. He could very well have an issue with his truck.

back in 01-02 trailer life mag. tested the d-max and a heavy trailer combo .
iwas suprised that the mpgs were listed at 17 solo 10 loaded . the trailer was listed at7000lbs to 9000lbs and they drove it on mostly flat surfaces.
my truck tows 8000lb trailer mpgs are 9.5 to 10.8 so far .empty it gets 17 .truck has 10000 miles on it and the temps stay normal 210 trans at 200 110deg outside temp . that dam fan does come on alot

pay close attention to your speed/rpm. 1500 rpm (5th gear at 55) is way out of the power band. If I am going uphill at all doing 55, I lock out overdrive. That puts me at 2200 where this is a lot more power.

I have two max's and The 10,000 mile breakin thing may be true for some things, but both of mine pulled very well from day one and still do. I didn't see or feel any change with the power at any mileage mark that I could stop and say wow what happened. Sounds like you have a problem, not a breakin issue.

You guys having problems should try purchasing a tuner. There are lots of options and you can find good used ones for great prices as well. Another 40-60hp will make all the difference in the world. The transmission will take those hp levels all day long and you will get better mileage as well. You've spend $30,000+ what is another $500? You will not regret it and most companies even have a 30 day money back guarantee if you do.

I believe that "Wait till it Breaks In" = "Wait till you learn something about your truck" and Diesels in general.

That does not mean that there is nothing Wrong. Just have to be able to determine IF it is in fact a Problem.

Idahofox

I would like to install an 8" Fabtect lift. How is the ride, did you have to swap gearsand what about the front axle boots? I just bought an 05 4x4 CC and love it. Any advise would be very helpful.
:offtopic:
The 8" lift is nice, however you do lose some power with bigger tires. I've thought about changing my gears, but a programmer made all the difference in the world. If you do the Fabtech 8", make sure you replace your stock pitman and idler with Fabtechs.

For all those TX guys: I've beat stock 1500's when my truck was stock. Maybe I know how to press the accelerator a little differently. It's the one on the right?.....right?:cool:

I spent alot of time over on the lb7 side of this bulletin board and noted the following with the lb7.

1. Fuel mileage drops off quickly at higher speeds. With the lb7 - over 68 mph and things drop off quickly. This is on a flat grade - the sweet spot in terms of efficiency is running the motor at 1800-2000 rpm (unloaded).

2. It takes 10-20k miles for a diesel engine to break in. If you look over in the lb7 section - you will see similar complaints about being unimpressed when the truck was brand new - all changed their mind after getting some time on the truck and letting it "loosen up". If you look on the cummins website - it says 20k miles. On my lb7 I noticed better mileage and smoother accelleration as I hit 5k and 10k miles, making me think that some "breakin" was programmed into the digital engine controls. Based on what I read from others - it did appear that this break-in programming could be bypassed by using an aftermarket programmer.

- jeff

I can't speakm for anyone else, but I can say that my '05 pulled like a champ from the word "go". I added the predator after only about 5000 miles. The truck now has about 12,000 miles on it. I didn't notice any improvement in power or MPG at the magical 10,000 mile mark. Maybe it's because of the programmer, or maybe it is all a myth.......who knows?
It has never run hot or felt like it was working hard. Also, I rarely hear the propeller er, I mean the fan kick on. I live in Alabama so it gets hot and sticky here.

Sack Head and all you others out there.
This so called lly that is supposed to have more ponys than the lb7 is bull. Just got my new one today ( lly) and it is a slug compared to my dually an it is a 3/4 2wd. Sure hope this does a 180 as it so lazy in 1st gear its pittiful. Seems like the turbo has to spool up before it even wants to make any h/p. I would deffinetly be in trouble if I had to hook on to a trailer an go some where.
Super Diesel
Why don't you come up with a electric fan that will work on these things, Ill be your first customer. It sounds like a Okla Tornado when it comes on an that is another thing, my dually fan has never came on even when loaded with the camper an pullin the boat. This thing may get chipped before the breakin an it is deffinantly gonna get a gutted c/c and a streight pipe so it can breathe better.

O YA AN A UNI FILTER GONNA GET PUT ON:ro)

You guys having problems should try purchasing a tuner. There are lots of options and you can find good used ones for great prices as well. Another 40-60hp will make all the difference in the world. The transmission will take those hp levels all day long and you will get better mileage as well. You've spend $30,000+ what is another $500? You will not regret it and most companies even have a 30 day money back guarantee if you do.

Which tuner do you suggest for the above application I to tow a 9000lb toyhauler and would like a little more ompphh! plus, it nice to know you have the extra power there in case you need it:exactly:

JLew

:offtopic:
The 8" lift is nice, however you do lose some power with bigger tires. I've thought about changing my gears, but a programmer made all the difference in the world. If you do the Fabtech 8", make sure you replace your stock pitman and idler with Fabtechs.

For all those TX guys: I've beat stock 1500's when my truck was stock. Maybe I know how to press the accelerator a little differently. It's the one on the right?.....right?:cool:

It doesn't count when the other guy doesn't know you are racing! :lol:

Tundra vs DMAX no way

Pull 10000 + at 85 with a tundra, can't do it



First, let me say that I think the 10,000 mile break in isn't going to be as dramatic as some would lead you to believe. If you are having that much trouble pulling that light of a load, then something is wrong. Your dealer will never find the problem until whatever is wrong goes from bad to broken. However, you should go to the three closest dealers and ask to speak to their diesel expert. You might get lucky and find one that just fixed the problem for another guy. Remember, not every dmax owner is a member here so there are guys with problems that never get on this website.

Lastly, let me say this. Stock for stock, my Tundra will whip the asbestos of any stock dmax. However, put a tune on a dmax and set it to even the lowest setting and I'll be breathing diesel for the rest of the day. I know, I've owned both trucks!

...This so called lly that is supposed to have more ponys than the lb7 is bull. ...

Got Dyno? :D

We've been hearing that the LLY sucks from the LB7 guys for awhile now.

On a dyno, an LLY pulls 5-10 more ponies bone stock. So they say, "yeah, but you cannot come close to the HP we can make by tuning an LB7!"

Well, we are about where the LB7's were 12 months ago in "tuned" HP, and climbing. It would not surprise me if we exceed LB7 HP by the end of the year.

I too was dissappointed with my 05 dmax on its first pull with 1300 miles. My previous truck was a 2003 chevy 6.0 crewcab. With the 6.0 pulling 9000 lbs to pinecrest CA I would get 8 mpg round trip and pull the grade at 45 in second gear 4400 rpms. With the dmax I was expecting 60 up the grade and 10-12 mpg. The first part of the trip I was getting 10 mpg then I hit the grade and and the fastest I could go was 50 mph floored, fan was making more noise than my 6.0 tached at 4500 rpms and by the time I got to the campground my mpg was only 6.6. Needless to say my camping trip was not good after the dissapointment of the dmax. My round trip gas mileage was 8.5. Hopefully someone on this fourm will have the answer to why our trucks are not performing like thiers. I would hate to go through the lemon buyback process again.
I just drove the same highway this weekend. I went to eagle meadow which is 5 miles before dardinales. I do this same trip every year we do a poker run for the 4x4 club I belong to. Last year I pulled the same load with my gasser and it was hurting up the grades. This year with my dmax I could drive as fast as I wanted to with no problems up the hills. I don't know the weight, back of truck full to the top various items raffle prizes. 16' car trailer with winch on front and tool box, yj jeep and 10 4x8 tables on the trailer. Also my tire and wheel package is a lot heavier than stock.

Rat
Im talking bone stock, Im serious this thing is a turd.

Get it dyno'd. Or take it to the track. SOTP meters aren't accurate as there is no requirement for annual calibration of pants.

Let's talk about the dyno!

Nobody here knows me, but I have been assisting some of the guys here in resolving the LLY overheat/underpower issues on the record setting thread everyone falls asleep to.

The last week, we have made some very startling findings, that completely explain what is happening to a lot of you. Haven't quite discovered why it is unique to the LLY...but that's another thing. Back to the dyno.

If possible, head to a dyno (somebody with the power, heat and fan complaints) where you can get loaded up for 10 minutes (I don't know dyno capabilities) and heat that sucker up. I mean to the floor, under load, for 10 minutes, at 2500 RPM, tall gear. None of this 10 second stuff. Monitor IAT the whole time, and then plot it against the HP as it decreases over time, yes HP decreases over time. The hot d-max is building heat, that's going right back down the throat in the underhood air box. We saw 221 IAT this weekend before pulling over, a full 120 degrees over ambient. That 221 into the VVT by way of the airbox. VVT outlet temps near 500 degrees. I calculated that HP was down to 140-160, half. It won't produce power with air out of the oven, basic ICE science. There is a big difference between slapping a 350Z in a 80 degree quarter mile tuned drag, and pulling 12 K up the desert slopes for 15 minutes. You'll swear it's a different truck.

Get ECT's up to 220, 230, 240 and you'll see what is happening.

If looking for something to do, read the last 10 pages of the overheat thread. There are some solutions that are being tested.

A quick dyno reading is not going to show what is happening in this thermal feedback loop, as it is dynamic and requires time under constant heavy load to develop. And a tuner is not going to make this go away.

Tundra vs DMAX no way

Pull 10000 + at 85 with a tundra, can't do it

1. Didn't spend $40,000 for the Tundra!
2. Never pulled more than a 2500lb boat with my Dmax...I overbought when I bought it.
3. Used 2 quarts of oil on last oil change with my Dmax w/ 36,000 miles on it. Didn't pull a thing on that 10,000 mile interval.
4. Stock for stock, empty, I'll whip you in a drag race.
5. If you tune yours 40hp, you'll whip me every time.

Because every repair costs a fortune with a Dmax, I wanted rid of it. Do any of you know what a new starter for one costs? It's a lot. Don't get me wrong, I miss my diesel when I fire up in the morning...miss that purr. But, I don't miss the rest of it. I never needed a 3/4 ton truck. If I ever do, I'll probably buy another Dmax. However, I'll be sure I can afford it without worry next time. As a self-employed person and a new daddy, I just didn't need the overhead worry I had with it. And for those of you about to write back about the 100,000 mile warranty. I drove my dmax for 10 months and had 36,000 miles on it. I owned it for 12, but was in Ukraine for2 months so that doesn't count. I've owned my Tundra 3 weeks and 4 days and have 3100 miles on it. I drive a lot. Warranty won't last long. That's enough of my :rant:

By the way, Justin at ValMark Chevrolet in New Braunfels, TX is the best service writer in the history of service writers. If anyone in Austin/San Antonio area has trouble, he's your guy!

McRat
I did take it to the track for comparison last week.
17.926@79.13
81 degrees and 18% RH

Truck was great from the stand point of engine temp. Cooled the whole time in the staging lanes with the hood up. Entered the lanes with sub 200 water temp and it felt much better than normal highway operation. Good power brake at the line and a small amount of tire slip on launch (surprised I got any as normally on the road it wont get any when at normal operating temps)

As far as Dyno, I did take it to ATS for evaluation (I live very close to them) and they reported it to be lower than typical lB7's but did not give me detailed info. Not sure if they did do much for evaluating as they did not charge me anything. I refuse to hop up something that seems not to be right.

KillerBee,
Are you saying the pre-turbo IAT gets that hot? I have heard from Kennedy Diesel that the LLY does run much higher temps aft the turbo and intercooler but the last time I talked to him he had not figured out why.

I don’t mean to be a sour puss but my particular truck is a dog and the dealer cannot figure as to why. If you don’t believe me than lets trade;)

McRat
I did take it to the track for comparison last week.
17.926@79.13
81 degrees and 18% RH

Truck was great from the stand point of engine temp. Cooled the whole time in the staging lanes with the hood up. Entered the lanes with sub 200 water temp and it felt much better than normal highway operation. Good power brake at the line and a small amount of tire slip on launch (surprised I got any as normally on the road it wont get any when at normal operating temps)

As far as Dyno, I did take it to ATS for evaluation (I live very close to them) and they reported it to be lower than typical lB7's but did not give me detailed info. Not sure if they did do much for evaluating as they did not charge me anything. I refuse to hop up something that seems not to be right.

KillerBee,
Are you saying the pre-turbo IAT gets that hot? I have heard from Kennedy Diesel that the LLY does run much higher temps aft the turbo and intercooler but the last time I talked to him he had not figured out why.

I don’t mean to be a sour puss but my particular truck is a dog and the dealer cannot figure as to why. If you don’t believe me than lets trade;)

That's about as quick and fast as our CC/LB 4x4 and jives with the magazine tests.

It doesn't count when the other guy doesn't know you are racing! :lol:
:funnypost:lol: Yeah sooooo!

Just Came Back From A 1500 Mi.trip Temt 90--100 Degree, Pulling 7000# Hr , 14-15 Mpg ,heard The Fan Once Or Twice ,and You Say Its Going To Get Better. "damm"
2005 ,250hd, Crew, Short,6.6 Dmax
Arsonguy

My $.02...

As you can see from my sig, I have an 05 2500 CC/DA. I pull 5,000 every weekend from 100-300 miles. So far, my truck has pulled like a champ in the Alabama heat this summer (85-95 degrees). My water temps have never exceeeded 210, my trans temps have never exceeded the "normal" operating range.

I traded a 00 Z71 5.3L and pulled the same trailer. There is NO comparision in these two trucks. Where the Z71 would stuggle pulling hills (downshifting or slowing down pulling hills), the Dmax never misses a beat. I set the cruise on 70 and leave it there... Fan only occasionally kicks in....

Something doesn't sound right with your truck. The fan should cycle as you describe.

Good Luck.

BeerMcCoy

Sack Head and all you others out there.
This so called lly that is supposed to have more ponys than the lb7 is bull. Just got my new one today ( lly) and it is a slug compared to my dually an it is a 3/4 2wd. Sure hope this does a 180 as it so lazy in 1st gear its pittiful. Seems like the turbo has to spool up before it even wants to make any h/p. I would deffinetly be in trouble if I had to hook on to a trailer an go some where.


My lly will outpull my lb7. It is anything but lazy, even bone stock. I pull a trailer regularly and have had ZERO problems. My Dad pulls a 36' 5'er with his 04.5 lly. Also, ZERO problems. He is a former Cummins owner and he is impressed.

KillerBee,
Are you saying the pre-turbo IAT gets that hot? I have heard from Kennedy Diesel that the LLY does run much higher temps aft the turbo and intercooler but the last time I talked to him he had not figured out why.


221 degrees at the air inlet, pre-turbo, a heat soaked motor that was pulling hard with heavy hi-drag load. See all the details on the overheat thread. It would seem the underhood air intake is not a smart design for a working truck.

I am not exactly sure of the specific heat added to the LLY, guessing EPA. If HP is actually more than the LB7, could be the cooling system was already at it's limit on the LB7, cause it's not working that well on the LLY in the summer where there are hi-temps and terrain.

The 05, by most reports, appears to be a better truck the the 04.5, that is, produces less heat accumulation underhood.

on edit: this is not true, there as many or more 05's with the issue.

There again, it may be the Chevy that cools better, with it's new design changes. It would help if everyone included Chevy or GMC in the signature.

1. I never paid 40000 but 33500 brand new
2. 4800 mile trip and used no oil
3. What repairs are you talking about, I had none.
4. You just never wanted a DMAX and had to complain to yourself to convince yourself something was wrong.
5. Hope you have fun with your toy.



1. Didn't spend $40,000 for the Tundra!
2. Never pulled more than a 2500lb boat with my Dmax...I overbought when I bought it.
3. Used 2 quarts of oil on last oil change with my Dmax w/ 36,000 miles on it. Didn't pull a thing on that 10,000 mile interval.
4. Stock for stock, empty, I'll whip you in a drag race.
5. If you tune yours 40hp, you'll whip me every time.

Because every repair costs a fortune with a Dmax, I wanted rid of it. Do any of you know what a new starter for one costs? It's a lot. Don't get me wrong, I miss my diesel when I fire up in the morning...miss that purr. But, I don't miss the rest of it. I never needed a 3/4 ton truck. If I ever do, I'll probably buy another Dmax. However, I'll be sure I can afford it without worry next time. As a self-employed person and a new daddy, I just didn't need the overhead worry I had with it. And for those of you about to write back about the 100,000 mile warranty. I drove my dmax for 10 months and had 36,000 miles on it. I owned it for 12, but was in Ukraine for2 months so that doesn't count. I've owned my Tundra 3 weeks and 4 days and have 3100 miles on it. I drive a lot. Warranty won't last long. That's enough of my :rant:

By the way, Justin at ValMark Chevrolet in New Braunfels, TX is the best service writer in the history of service writers. If anyone in Austin/San Antonio area has trouble, he's your guy!

Stock Duramax would smoke a Z-71 or a Tundra. Read the "Kill Stories Forum"! I tow a 10,000#+ trailer in all ranges of temperature on 37" tires. I'm very pleased with it's performance, however I too hate the fan! Give it time to break in.

If you are talking about empty trucks you can't be serious... I have owned 2 Tundra's prior to my '05 GMC Duramax. In unloaded form it is barely even a race on the '04 and older Tundra's, on the '05 Tundra's the engine was upgraded to VVT and a 5-speed tranny now they are getting into Titan and Hemi Territory simply because the Tundra weighs very little. In loaded form no gasser will run with a Diesel....(especially if you throw in their stopping for more gas)....as for the kill stories it is amazing what some people can dream up. -:t

Here is a little fun we had at my shop with a Ford and a new trailer we built:

http://www.dieselplace.com/forum/attachment.php?attachmentid=6389&d=1121307913
Looks like the boy dog is getting ready to mate with the Toyota):h :joke:


I'm pleased with the way my 05 tows. The fan comes on some but at 95* with the A/C on I expect it, and it seems to hold right at 210. I averaged 13 towing my 4000# boat with lots of wind drag. I admit that I drove my last tank easy never went over 75 but I averaged 18.3 and I only have 2K miles on it. I only have two trucks to compare it to. The Z-71 5.3 I sold and a buddies 2K Dodge / Cummins. My new D/A put both of them to shame with the same load. My 5.3 averaged 16 and got 10.5 with that load. The Dodge averages 17 and got 12 with the same load. While the 5.3 spent most of it's time in 3rd it saw 2nd a few times. The Dodge held OD on most hills but saw 3rd a few times. The D/A NEVER downshifted.:cool:

[quote=speedrcr;627290]http://www.dieselplace.com/forum/attachment.php?attachmentid=6389&d=1121307913
Looks like the boy dog is getting ready to mate with the Toyota):h :joke:

:exactly: :funnypost :lol:

[quote=speedrcr;627290]http://www.dieselplace.com/forum/attachment.php?attachmentid=6389&d=1121307913
Looks like the boy dog is getting ready to mate with the Toyota):h :joke:

:exactly: :funnypost :lol:

That's just sick!:lol:

To compare apples to apples: Thick hot air on flat land is NOT SIMILAR that thin hot air in the mountains - at least not with the LLY!

I traded in a 2001 tundra on my GMC. I have to say for what it was it was pretty nice. I thought I would really miss it but I don't. See the let down to me was the problems I had from 5000 miles on. I was expecting that legendary Toyota reliablility. My truck had both exaust manifolds replaced by 15000 miles and the engine developed a serious tick that came from the block. Piston slap so loud it was embarassing. I think GM could take lessons on fit and finish, but overall I have more confidence in my GMC.

I was in 4th gear as opposed to 2nd, but with the fan on, the power seems to disappear. Jerry.

Ok... I haven't read this whole thread yet but I have to chime in on this. If you lug a diesel you will shoot EGT's thru the roof. The difference between a gas and diesel is the diesel will make the power to hold a gear longer than the Gasser, but at the expense of heat. This doesn't mean you need to wind the piss out of it to get the job done either. A good investment would be a EGT guage. I personaly wouldn't let the EGT's get much over 1200 before manually downshifting. There most definately is a difference in how to drive a diesel as opposed to a gasser in my opinion. Good luck and as always verify what you read with someone you trust.

Let the dam engine break in!!! Let the transmission learn your driving style. 10-15k break in period is for the pistion rings to seat into the cylinders so the pistons seal the cylider and establish adaquite compression. Think of something like this, TDIs work the best when each cylinder is at 580psi TDC, but this doesn't happen till 60k. When i first got my truck 14-16mpg gallon unloaded.....after 14k 17-21mpg and plenty of power so till then just drive and smile when you get to 13k. Theory on the engine fan....although it is a thermo clutch, it also it computer controlled to turn on when ever the a/c is on. I think it kicks in more when the engine is not broken in properly. When the engine is not broken in yet the engine has a decreased power output, so when you have to floor it up hill because of the lack of power at the moment, speed sensors notice that the truck is not accelerating as fast as it should when it is floored. Now when the ECU sees that it might think that the engine is overheating because it is not producing power, on goes the fan. I am not a GM enginner nor have i read skematics for this truck but the fan does its job.

my truck has 25K miles on it and the fan kicks in all the time, even when I'm not towing. If I just let it idle for a few minutes and jump in it, most likely my fan will kick on. Going down the road even while pulling it doesn;t come on though.

I think you must be confused on the fan clutch operation. It is not electronically controled.It is temperature viscus applied only. It has no pcm input or influence.It does not see any wheel speed or load. It senses air temp through the radiator/condensor stack only. It does not know engine cooolant temp.Airflow temp only. At predetermined temp specs the viscus flluid engages the clutch at different friction ratios.The fan clutch hub then transmits pulley rpm to fan rpm.The only reason it is louder with the A/C or after you sit and idle is the air temp across the radiator/condensor is higher due to thermal loading.The trailblazer has an electro/viscus fan clutch but not the duramax.

I did want one, but found I didn't need one. Remember, in the rest of my post I said I would buy another one, but not until the situation is right. As for complaining to myself, maybe that is true. But I wasn't dreaming or imagining the problems I did have. I don't think the other people on this forum are dreaming or imagining their problems either. I doubt their trying to convince themselves that anything is wrong. Rather, they are hoping that everything is alright! Lastly, comparing Toys to Dmaxs is like comparing apples to ball bearings. They are 2 different animals.



1. I never paid 40000 but 33500 brand new
2. 4800 mile trip and used no oil
3. What repairs are you talking about, I had none.
4. You just never wanted a DMAX and had to complain to yourself to convince yourself something was wrong.
5. Hope you have fun with your toy.

how can a fan drag down a motor with 590lbs of torque

or does it cause it to defuel when the fan comes on

is this the way that gm solved the cooling problem with the earlier models by causing the fan to come on all the time

Originally Posted by dmaxalliTech http://www.dieselplace.com/forum/images/misc/backlink.gif (http://www.dieselplace.com/forum/showthread.php?p=624558#624558)
To all who miss their gassers, I'm offering 10k cash for your new truck and I'll help you find a gasser to replace it. This offer limited to the first 3 to respond.


I going on a camping trip to Oregon next week so I'll see how my dmax pulls this time. I'am expecting to get 10-12 mpg and 60mph min with 9000lbs. If it can't do that then I might take you guys up on your offer.
I would like you to replace it with the same truck except 6.0 gas.