I recently rec'd my 2005 Durama/Allison 2500HD. I will be towing a 7700 lb trailer. Total GCVW will be about 15500 which is about 6500 under max GCWR.
My truck has the haul mod and I know that most of the time it is suggested that you tow in D not O/D so here are some questions because I am debating whether to add a pyro and boost gauge and this may help me decide.
1. On flat stretches on interstates are most of you running in O/D or D?

Many say that the turbo temps climb to very high temps because some are running with mods and others are flying up the grades in high at 709mph.
SO next question.
2. What is the best means of keeping those temps in check when climbing a long steep grade like the Grapevine?
A. Running at a RPM of about 2500 in what ever gear will provide it?
B. Getting out of O/D and just downshifting to keep in that range as you go up?
Or what?
I spoke to DuraMaxTech and he said if I don't mod engine then gaugegs although nice are not necessary. With that in mind I want to know what generates exactly these high turbo temps and what can I do to avoid them.
Further If I do put a pyro in, it will be post turbo as I do not want to take the chance of the probe coming off and going through the turbo.
If I were to only have a boost gauge can it be used to control turbo temps by staying with in certain operating ranges (boost levels)?

It would seem to me that if one drives sensibly as most do and gives the engine a cool down after climbing a grade should they wish to stop then that they would not run the risk of over heating the turbo and frying the thing.
Of course I would presume that after a long grade climb and a few miles of level or down grade driving the turbo will cool itself.

What I want to find out here is what driving methods and habits can I adapt to keep these under control normally whether with gauges or without them.

Thanks
Bobhttp://www.dieselplace.com/forum/images/smilies/rockon.gif

Gauges? Yes, by all means. I wouldn't worry about breaking a thermocouple and running it through the turbo. Most of those "in the know" really advise that a pre-turbo pyro is best.

Towing in fifth gear with the Allison is not a bad thing at all. If you pull in Tow/Haul like the engineers had in mind, you'll find that the truck will shift into fifth (OD) when conditions are correct. If you're in a headwind, pulling a hill, etc., she'll want to stay in fourth. If it does start to "hunt" between fourth and fifth, then use your overdrive lockout to keep this from heating up the tranny.

Hope this helps.

I have never lock out overdrive. No reason to unless you are getting high trannie temperatures or you are rolling to fast downhill. MPG would be horrible. My payload and trailer weight are about 6000 lbs and I don't really even need haul mode except on downhills. I always use it though because the downshifting does slow you faster, saves the brakes. MPG is only better with tow mode off going 45-50 mpg. Sometimes I will toggle out of tow/haul if cruising at 45-50 for long periods when towing. I also use tow/haul when mountain driving empty. I recently did the pretty servere 15+% grade between Study Butte and Presido Texas on 170 towing and had no problem. I took my time and the truck stayed in 4th on its own. No overheating of engine or trannie, not even close. About 80-85 degrees out too.


I absolutely hated screaming at 3000 rpm plus with my gas Sierra with OD locked out. Destroyed the truck in no time and rattled your brain. Humming along in a D-max is like heaven

If your truck is stock just put it in gear and put the hammer down. You won't hurt anything.

I haven't had a shot at the Grapevine yet, but have pulled both Cajon Pass (Monday) and Churiaco Summit (outside Coachella). I was at about 20k both times. On both pulls, temps flitted around 1250, and I was in 3rd gear. I do have a 4" exhaust. My truck is also a '02, and I know there are some major differences.
What I have found is that as you increase altitude, you loose boost and increase temps. That is where a EGT is a necessary item. I also have both pre and post turbo EGT, and under some conditions, the post reads 500 lower than the pre - install it pre!!!
Unless I start hunting between 4 and 5, I leave the OD lockout off.

RobertM, first/foremost congrats on the new truck and welcome to the DP family! :D Your posts kind of reminds me of another guy that joined back in August 04. Have you posted the infamous "I'm going to leave my truck stock" statement yet? ):h

There is a considerable amount of torque available at very low RPM's. You will find the Allison does a good job of holding 5th gear, especially as light as you are towing. Like Horse Trainer posted unless it keeps shifting between 4th and 5th I would leave it in O/D. The tranny will run cooler as well. The Allison is one smart tranny, let er' do the job. :ro)

As for high turbo/exhaust temps you can have these without mods or trying to tow at high speeds up hills as well. I can easily peg 1250 degrees on a good hard acceleration with nothing behind me. It's sustained high EGT's that you want to watch for. Unfortunately without an EGT gauge you just don't know what they are. EGT gauges should come stock on these trucks regardless of whether you tow with them. Excessively high EGT's can steal the life out of your engine. If you are doing any towing you need at least a EGT gauge, pre-turbo IMHO. :cool:

As far as keeping EGT's in check you have several options here. You'll find plenty of discussion on the DP about this if you do a search. You are towing pretty light at 7700lbs so keeping EGT's in check is a bit easier. Cranking those RPM's up above 2500 while towing is going to increase boost considerably and conversely raise EGT's. You will also notice the engine and tranny temps will start to spike upwards. Best to keep RPM's a bit lower and backdown on speed as necessary. I elected to go with an aftermarket programmer and bigger exhaust to hold grades better and actually lower EGT's. :rolleyes: Plenty of intel on the Power/Performance forum. :confused:

Horse Trainer's comment about high altitude and boost is something we're looking into in another thread. Seems some 04.5 LLY's have experienced overheating issues under these conditions, albeit most were towing pretty heavy at the time IIRC. Once the outside temps start climbing again we'll likely see that post re-ignite. GM is supposedly working on a fix for this, your 05 may be OK. ;)

If you take your time and drive reasonably you should be able to keep your EGT's, engine and tranny temps within reason. If you start towing heavier, say over 10k lbs your variables will change considerably. You might read some of the posts in the towing/trailering forum. Several of the guys that monitor that site have extensive experience with towing and are very helpful. :exactly:

Hope this helps. EGT gauge would be my highest priority, did I mention pre-turbo? Enjoy your truck, oh yeah, uh get out your checkbook cause I see'z some mods coming your way! ):h JJ :)

I purchased my duramax/allison crew cab dually in December. I have an 11,500 lb trailer that I tow and a self contained Fleetwood camper that I put on the truck as well. I am really looking forward to hooking it all up and taking a trip. Hearing you guys talk about all of this makes me want to get out there and get rolling!! http://www.dieselplace.com/forum/images/smilies/smile.gif

http://corvetteforums.net/evefiles/photo_albums/9/2/4/924104297/414104297_CB8A7C681A0FE7CF1A3A71F50D70E8A5.jpg

:ro)
http://forums.corvetteforum.com/photopost/data/1078/11249P41800111-med.JPG

Thanks for all the replies. It really helps. I will most likely go with the EGT pre turbo if I can locate an installer I trust. Post if I cannot. I think knowing anything about temps happening in there will be helpful stock or modified. If I go post turbo I will give myself a bit of a fudge factor using 800-850 as my max allowable temp. I presume this would be in the 1250 ball park pre turbo and I also assume that these temps are not meant to be maintained any longer than necessary.
I will also install a boost gauge
That brings up another thought or question.
I have heard that the optimum efficiency of the engine is at a turbo temp around 600 this affords best combustion to mixture etc. This is not my formula or opinion just what I have heard. I also have heard that the boost gauge is the best way to know not only what the turbo is doing but by using it you can optimize mileage.
So boost fellas what signs and things should I look for in observing my boost gauge to use and drive most efficiently?
Thanks
Bob

I would honestly be suprised if 7700 pounds even worked the truck. Put it in drive and hammer down! Mine pulls a 10,200 pound boat like it's not even there... NEVER has it shifted out of overdrive at a steady 70. Ok, one time it did, but I was flooring it to see how much was left.):h

I think you'll be suprised how easy it will pull it....:ro)

Personally I would think about installing the gauges yourself, it's a simple job and it may boost your confidence about maintenance issues in the future. I installed mine in about two hours. Time and patience is all you need-- and maybe a few tools.
I recommend removing the manifold to ensure removal of all metal particals.

When I instally my pyro, I'll use the hoot method. (drill/tap with engine running to blow out metal.)

Truck will pull 7500 half asleep. Use Tow/Haul and forget about it.

Showing my ignorance again. What does an EGT guage monitor? I'll be pulling 16-17k of 5'er in the mountains and per JJsDuMax post, it sounds like I should have one. Have 3500 Duramax with LLY on order. Guage easily installable for novice? Recommendations on manufacturer? Any other vitals I should be watching that GM doesn't provide for?

EGT stands for Exhaust Gas Temperature

Gauges very simple to install, just follow directions provided. If you run into a snag just ask. Plenty of help on this site.

Gauges very simple to install, just follow directions provided. If you run into a snag just ask. Plenty of help on this site.
Does anybody sell a pillar pod that does not require drilling into the factory pillar? I'm still trying to decide which mounting method to go with.

I saw on this site someone was selling a gauge kit that went into the overhead dash (console) with EGT, AND Boost looked cool. Maybe someone can chime in. Where did I see it??????

Try this link it is a walk thru for installing them in the overhead well.
http://www.bmdmax.com/Gauges.html.0.html
Here is the site where you can buy the face plate.
http://www.socaldiesel.com/

Hope this helps
Bob

Yep that's the one I was Talking about.....
Thanks

Does anybody sell a pillar pod that does not require drilling into the factory pillar? I'm still trying to decide which mounting method to go with.
Sledman,

None that I know of.

There was a move afoot to get some custom OEM style pillars with gauge pods but the min order was up there a ways and there were too many interior colors to deal with.

Don't worry about drilling into the OEM A-pillar cover, I don't think they're too expensive to buy if you want to return to stock. Just order another one and keep the original for a backup.

You really don't care how you screw it up after having to modifiy the Bose tweeter mount in both pieces to make it fit correctly.

It cost me 300 bucks to get my banks thermocouple installed, at a local exhaust shop