All,


I finally had the chance to tow with my duramax to see how it would do, and I gotta tell ya I was a little disappointed. For some reason it only maxes out at 60MPH uphill. My 2003 CC 6.0L with the Hypertech III could hit 75MPH up the same hill. When I am on level ground the D-Max does alot better than my 6.0L just starting out and at lower speed acceleration, but once you hit a hill, theres not much excitement going on. I had it mashed to the floor pulling a 5400lb trailer. Is this normal??? I love this truck, but I expected more from the diesel than 60 with a little trailer. Could someone help me with this....Thankshttp://dieselplace.com/forum/smileys/Ermm.gif

you have got issues.....


I can do 75 up 6% grades with my 12k fiver easy.

is yours stock??? This thing is an animal on level ground but weak on hills. I just got it 3 weeks ago used. It had 29000 on it and runs great, but it just doesn't like hills.........................

Did you have your overdrive lockout on? Maybe it wouldn't shift into 5th and you were limited by RPM?

Fuel Filter? Something is not right with your truck!

I have found that with my stock truck that if you keep it mashed to the floor, it will not downshift and you slow down. If you let up on the peddle a bit, then it will down shift and you will speed up.

I've pulled 10-12k with mine stock through the hills of East Tennessee and I easily maintained 70-75 MPH. I'm with the "you've got issues with the truck" party.

It seems like it needs to grab a lower gear. It was spinning about 2200 RPM and not moving. (in TowHaul mode). I took it out of OD but the rpm's were to high. I took it out of TowHaul mode and there was no change. On level ground taking off this thing feels like it will tear the trailer into two pieces. Really good power. Its just the hills that make this thing powerless. Could it be a fuel starvation problem?? Not neccessarily one that would cause the cutting out of the engine under high loads, but just rob it from making any real power under high loads??? Under normal conditions, the truck runs great.

You've got issues for sure, my TT is about the same weight as yours and I have to set cruise control to keep speed LOW enogh to stay out of trouble! I mean if I just use throttle, first thing I know, a glance at speedo shows I'm like pushing 80-85, regardless of hills!


Start with a fuel filter and air filter. If that doesn't do it, then get fuel pump and injectors checked.


But by ALL MEANS, come back and tell us what you find so that we can all share in the solution. Too many times we all offer our ideas and the guy with the oroblem finds the solution, perhaps from our help, and doesn't come back and tell us what he found!

just noticed you have a K&N filter, I would try cleaning the MAF sensor first and foremost. Then go to the fuel filter and air filter. Make sure your basics are ok. After that......how does it run empty? Does it downshift or just run out of power?

My 03, when stock, pulled my 6200 lb travel trailer at 70-75 with no problem. I have hit a few grades in MI that made it work a little but nothing serious. Even with OD locked out you should be able to run up to 70+ MPH. My bets are the fuel filter or an oil-fouled MAF.

GMan915,


I have a CC LB Dually and can easily tow up 6-7% grades at 70+ with my 11K lb enclosed car trailer. That also was with 4 people in truck and AC on. I would say something is not quite right. I agree with DMaxAlliTech, I would check some basics.

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<TD id=HB_Focus_Element vAlign=top width="100%" background="" height=250 UNABLE="off">i agree with darin...don't floor the pedal and it shud shift fine...mine pulls my 18' stock trl, 2 ponies and a carriage with NO trbl at all! http://www.dieselplace.com/forum/smileys/Big Smile.gif</TD></TR>
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you sure yours has the dmax in it? mine idles up the mountains and through the woods 65 mph juice level 1 4th gear. one of these days ill open it up and see what she can do.

oh yeah forgot i was pulling about 9000#

UPDATE I changed the fuel filter in it last night and cleaned the MAF Sensor. I pulled the trailer again to see any difference and outside of a little better fuel economy running empty, it still wont do much more than 60MPH on the 6% grade pulling the 5400LBS trailer. My 6.0L pulled the same hill at 75+. Today its going back to the dealer to get a checkup. On level ground this thing runs strong without the trailer, it's just the hills where it shows the problem. I'll let everyone know what the dealer says...Terry

Yes, please let us know what it turns out to be.


Your Max is feeling http://www.dieselplace.com/forum/smileys/Dead.gif


My toybox is right about 9K loaded and I can go up our big pass in the area without the truck even breaking a sweat!

Hey, I just thought about this!





Is your brake controller acting up? maybe its dragging the trailer brakes on the hill??

Yeah, there was a post like this some time ago. With them changing the wires around on the plug, the brakes would be on if you were using an old pigtail.


That could be your problem when towing the trailer.

You have got me thinking about this now.......The dealer has moved my brake controller over to my new truck. But he failed to move the fuse. By default is the brakes applied on camp trailers with electric brakes and the electrical circuit of the trailer brakes releases them??? I wouldn't think so. (big airbrake trucks have the brakes spring applied and pressure released). Any input on this possibility?????

They are applied by power. They are released when power is no longer applied.

If you brake controller is from a pre 03 truck the brakes will be applied at night as soon as your headlights come on. During the day they will not be applied unless you manually turn your park lights on.

Here is the post that I was reffering to.


http://dieselplace.com/forum/forum_posts.asp?TID=139&amp;PN=40

I can pull my approx 9,000 fiver up some real hard pulls here in Oregon at 70 to 75 mph without so much as a hic-cup.My truck is stock as stock can be except pre racor fuel setup.I know that aint making no horsepower.http://www.dieselplace.com/forum/smileys/Cool.gif

Hello All!! I cannot believe that someone else is actually experiencing my problem.http://www.dieselplace.com/forum/smileys/Clap.gif My truck runs great...just as mentioned above. I have suspected problems pulling my 9000 to 9500 pound fifth wheel. I have posted several post on the Woodall site but no really good recommendationshttp://www.dieselplace.com/forum/smileys/Ermm.gif. Everyone seems to think that 60 to 70mph with a 9000# trailer without downshifting is perfectly okayhttp://www.dieselplace.com/forum/smileys/Big Smile.gif. The problem is I don't seem to have much throttle after that. gman915 - If you resolve this problem please post the cure!!! Fuel filter, air filter and oil change made no noticable difference. HELP!http://www.dieselplace.com/forum/smileys/Cry.gif

I pulled my 28' 12K 5er last summer, I could hold 70 to 80 mph just about on any highway grade. What I did learn is if I held it around 60 to 65 my fuel millage greatly improved. I had no problems with power.

One question. I do pull in tow haul mode but I do not disengage over drive. When pulling, does everyone use tow haul mode and disengage OD or do you just use the tow haul? Hope this makes sense!!http://www.dieselplace.com/forum/smileys/Confused.gif

Terry;





What altitude are you at when hitting this hill? What are the outside temps?





Elvis

only 3000ft at the top of the hill.....Temp was 70F

It could be your 285 tires. I experienced a noticable performance drop while pulling my 7500lb 5th wheel after switching to taller tires. I really didn't expect any difference, but you can definitely feel it. No power adders on mine, yet. I've been told that would take care of the loss in powerhttp://www.dieselplace.com/forum/smileys/Big Smile.gif.

I put 285's on my o4 and I wasn't expecting a change but you could feel a power loss. I used the Bullydog Power Pup downloader and added the 75 HP tune, it really rocks now. Hold you to the back of your seat Power.

2200 rpm at 60 mph? you must already be in 4th gear. So with that said, something is wrong. 5000# behind a stock Duramax/Allison should have near empty power. That is no load at all. And in 4th gear, you should be able to pull right up to red line without much trouble.

Well the truck just got back from the dealer and, as I suspected, nothing was wrong with the truck(Good thing).http://www.dieselplace.com/forum/smileys/Big Smile.gif So that leaves me to believe that the trailer brake is in fact dragging some. I purchased an 03 harness for my other 03 6.0L and it worked fine in that truck. However it has been behaving different in the 03 duramax (like no trailer brakes). I suspect I have fallen victim to the blue/brown wire crossing problem in the wiring harness for the brake controller. I will just pull the controller completely to isolate the problem and report my findings to all....

I spoke to my dealership and of course they really did not have a clue. They did contact GM and they requested the following: (1) Hook truck to trailer (2) Bring complete rig to dealership and install the Tech II (3) Their diesel mechanic will ride with me under different driving conditions to try to monitor fuel pressure, air flow, etc. (4) Take trailer to the near by weigh station and get an exact weight. They will then evaluate the numbers based on trailer load, etc. Who really knows but I am going to try to schedule this service for sometimes next week.

Go to the bottem of the hill and stop, unhook your trailer plug. Get it on up the hill, stop at the top and hookup plug for brakes to go down. This should tell you something. Also if your trailer brakes were dragging your wheels should be scorching hot after a few miles of driving.

I'm going to give that try if and when it ever stops raining in south Louisiana! http://www.dieselplace.com/forum/smileys/Cry.gif

What is an "MAF" sensor?


I was towing a 5400# TT (GVW approx. 13k) this past weekend heading east out of Laughlin Nevada and there are some spots there where Topo USA maps indicate 10% grades--I was doing alright but didn't have to hold her back or anything. I think I had at least 65mph out of it and wasn't concerned, but if I should be getting 75 or 80, I want it!


thanks!


don


thanks!


Edited by: donmiller714

gman915,


Was this problem ever resolved? I have not had a chance to have my truck serviced with the trailer1

Well the problem was actually resolved, but not by the dealer. Edge products gets the kudos here. Talk about waking up this motor. It is so much more drivable now. It responds quicker to throttle input, has improved my mileage, and tows the wheels off my little 5400 lb trailer on level 2. For whatever reason in stock trim, my engine would just try and lug in 5th at 60mph. After a fuel filter change and draining all the fluids for the 25Kto 30K service. I got maybe another 5 mph on the same hill. The Juice made all the difference. I drove to a wedding in Baker City, Oregon from Boise and got 21.0 MPH by running 65 the whole way. Wow. Sure beats the 11 mpg I was getting in my 6.0L. Long story short....If you too are suffering from the same stock pulling woes I was, find a friend who has the Juice. Take a test drive, and try your hardest to chisel the S%@# eatin grin off of your face before you exit the vehicle.................Hope this helps.......GMAN

gman, just so you know the DIC is not accurate with the juice. If it said 21mpg, you likely weren't getting 21 mpg. You have to calculate by hand with a a power adder.

gman915,


Thanks for the update. Your reply is exactly in line with my thoughts. The truck just runs to good to have a mechanic problem (?). However, fixing a mechanical issue would be a lot easier to explain http://www.dieselplace.com/forum/smileys/Angry.gif to the little wife than the $800 spent on the "Juice". Somethings just take a little long to achieve.http://www.dieselplace.com/forum/smileys/HiHi.gif

Anyone have any comments on the eariler mentioned Bullydog Power Pup downloader? I'm starting to think that I want something like this!


thanks!


Don

tpcobb,


Sometimes asking for forgiveness is easier than asking for permission.......http://www.dieselplace.com/forum/smileys/HiHi.gif