40 k for a 1 ton truck that will not pull 8500 lbs

[Hunnington]

Transmission fluid scorched pulling 8500 lbs. Tranny temps 255 and engine temps 235 pulling 8500 lbs in some hills out east in 80 degree temps. Mechanic told me today there was nothing wrong with the truck and changed the tansmission fluid so if I pull again the same thing will happen. Does anyone know if GM has made this right with any owners like Ford did by buying back the latest early production Powerstrokes. It does not seem right that I have to fix the problem with aftermaket products but I know thats the way it goes

[Mark Rinker]

Whoa big fella! Back away from the ledge...you've come to the right place!

First things first - please fill out your signature profile with as much data about the truck (year/make/model/modifications/accessories). Then give us some background on the situation that lead to your tranny overheat. What speed did you maintain through those hills during the overheat? I recently experienced the highest water and tranny temps of my 20K mile summer in western Pennsylvania of all places!!!

I regularly haul 12-14K # 28-32' cruiser boats which are HUGE air brakes, dwarfing the truck, and maintain 210 degrees tranny temps at 70mph cruise control and air conditioning on. I can say that it is a function of DESIRED SPEED when it comes to running the hills.

Something SIMPLE is amiss...lets get our collective heads together and figure this out!!!

[SoTxPollock]

Hunnington, something else is wrong. I've pulled total weight of 35,000 and at times with the accelerator on the floor for at least 5 or 6 minutes on long hill accelerations and I've never scorched the fluid or overheated anything.
Your cooler may be blocked inside. The problem you describe has not been mentioned here that I recall where someone scorched the fluid in an Allison.
Better get it checked out again.

[Mark Rinker]

The only way I know to get the Allison that hot with that light of a load is for the torque converter to be unlocked.

If you have ever limped a heavily loaded DMax/Allison and decided to continue until its more convenient to pull over, you've likely seen high tranny temps and high water temps as a result - even if you drop your speed expectation back to 45mph or so.

I am pretty sure that the torque converter is unlocked during a limp, to allow the truck to accelerate from a stop in 2nd gear.

Hunnington, are you running any aftermarket power adders? Anything that would indicate that the torque converter isn't locking up while towing? What speed were you running? Tow/Haul engaged?

[Dave]

Transmission fluid scorched pulling 8500 lbs. Tranny temps 255 and engine temps 235 pulling 8500 lbs in some hills out east in 80 degree temps. Mechanic told me today there was nothing wrong with the truck and changed the tansmission fluid so if I pull again the same thing will happen. Does anyone know if GM has made this right with any owners like Ford did by buying back the latest early production Powerstrokes. It does not seem right that I have to fix the problem with aftermaket products but I know thats the way it goes

What year truck? I ask as there are three versions of the Duramax, the LB7 which is 01 to 04. The LLY which is 04.5 to 05. And the LBZ which is 06. there is also a 06 LLY which is not the same as the 05 LLY but closer to the LBZ.

My LB7 was a perfect truck. No troubles ever pulling up to 12,500 plus a harley in the bed.

My LLY was a overheating POS. I overheated it pulling 4000 pounds on the flats of MS and SD. I overheated it pulling 7000 pounds in TN, and again pulling 12000 pounds in TN. Pulling 12000 pounds it was 72 degrees out side. Trans hit the red zone, engine over 255 as it when into limp and shut down.

My LBZ is great, no hint of troubles or high temps.

GMC replaced my POS 05 with the 06.

[dieselrealtor]

Even good dealers get bad techs from time to time, if this is a dealer that you know & trust, talk to the service manager & request another tech to take a look. If you are in doubt, take it to another dealer that has a good reputation for doing a lot of service business on trucks.

I towed about 8500lbs (the melted duramax) behind my burb at 65 from Western Kansas to Indy in August with NO problems, what you are experiencing is NOT normal.

[jsmiracle]

I know it's been said several times, but I'll concur with the earlier posts that your experience is not normal. I tow >9k lbs. fairly regularly with my 05 LLY and never have had tranny temps > 215F ( usually<205F) and I have towed it over the Appalachians on a few occasions. BTW, the engine fan rarely comes on and engine temps are rock solid < 210F.

I hope you soon discover the correct root issue.....

Jim M.

[Kennedy]

We have trailered my 2002 out to MT twice, and Utah once. This is about a 12k load and we don't slow down. Trans temps never got out of line. Engine temps did hit 220-230 but that's not really a major concern to me. Sure I'd like it cooler, but...

[Albee]

I found that if I am pulling at slow speed around 15-20 mph up a steep gravel road going up a mountain and have the tow/haul mode off, my engine temp will climb above normal within a mile of the climb. Stop, put TH on, let the truck sit for a few minutes then continue the climb and temp stays perfectly normal for the remaining 8 miles of the climb. I have no idea why I chose to take TH off, but I did and that was my result. NO more TH off while pulling my 18K 5er. Good luck to ya.