Scorched Tranny Fluid

[Hunnington]

OK I will back away from the ledge, but it is so very disappointing after looking at these web sites for years and finally buying my first diesel and being so excited and proud about it, to find out it will not pull 8500 lbs up a hill without overheating. GM dealer is now telling me that they will order the parts to replace the air box whch will cool down the motor and in turn cool the tranny. My next question is does this work. Truck is a 2004 3500 4x4 LLY, 22,000 miles with no modifications.

[DmaxMaverick]

I'm not sure what they mean by "air box", under your description, but let them try. If it doesn't work, take it back. Let them fix something else, and try again. If anything works, then you will have a good truck, only suffering some inconvenience (which they should compensate you for).

In the meanwhile (on the QT), look into your state's lemon law requirements. Some states require a specific number of attempts to correct a defect over a specific period of time, then the manufacturer is required to buy back or replace your vehicle. If you use your vehicle in accordance with the manufacurer's specifications, and it overheats, it is not performing as advertised (what you paid for), and is defective. Do not mention the "lemon law" to your dealer until they have met all the criteria. It will only create friction. The best option is to keep the dealer "working" for you. Try to be polite, but don't bend over for them.

Good luck!

[Mark Rinker]

I once had transmission/transfer case issues with a 2003 K3500 (6.0L gas, 4L80E) that were repaired under warranty.

After the repair, the truck started to exhibit slippage in reverse when loaded with a trailer. I took the truck back to the dealer, they checked everything, and basically suggested that I not "tow such heavy trailers".

The next day, I stopped by with a properly loaded and tarped 30' gooseneck behind my truck, and asked the service manager to take a ride with me. The dealership's back lot has a pretty good grade to it, so I simply started backing up this grade until the transmission slipped, bucked and chattered enough for him to see.

2nd new transmission rebuild happened the next day. They had made a mistake on one clutch pack during the initial rebuild.

If you have a defective torque converter, transmission, or both. Don't give up, load the truck up and take your Service Advisor for a ride. Don't discount the whole package for a defect. You have a good truck, overall. We all can attest to that.

Question: Was your truck purchased used? If so, what do you know of its previous owner's use? Has it ever been chipped or turned up? If it was in the past, you might have glazed clutch packs, causing the slippage and overheat.

I tow commercially with heavy loads and can tell you that overheating can happen with everything functioning 'normally' if your torque converter isn't locking up or if your expected speed is too high. The difference between 60mph and 65mph under towing/grade conditions can be the difference between 210 and 260 on your transmission temp.

BTW, unless your temps were sustained for long periods of time, I really doubt that your fluid was 'scorched'. Replacement never hurts, and makes sense for the dealership to do if you brought them a truck that had been 'hot'. Did you see/smell the fluid? Was it red, brown or black?

I'd like to hear alot more detail about the conditions and situation leading up to this overheat. We may be able to find a root cause that will save you alot of headaches and time arm wrestling with the dealer, or pinpoint the componant that they need to focus on - i.e. torque converter vs. clutch packs.

[Kennedy]

The first thing that I would do is change the spin on trans filter. If it hasn't been done in 22k, that could well be a key issue.

The air filter change is the 2006 air box upgrade/update or whatever you call it. Be sure that they apply the proper ECM programming to match this box.

[Mark Rinker]

JK - is the airbox really improved? Anyone flow tested it over the stock peices?

Also what circumstances would allow the Allison to be towing, but not locked up? I think this is the root of his overheating problems - I have experienced the same once while loaded, limped, and in a traffic situation that would not allow me to pull over. It got hot enough to send a message to the dash (2001 layout) and set a TCM 'Transmission Overheat' code that my dealership recently found and cleared when doing my injector work.

I have since changed the tranny fluid and external filter, but it wasn't scorched at all. Still pink, not stinky, and probably not necessary. I was in the RED zone for 10-15 minutes with GCVWR of 25,500# on uphill grades western PA...big boat, uphill, headwind, hot day...

[Hunnington]

I purcahsed the truck new. and have cahnged the fuel fiter once and the transmission filter twice. This was the first time pulling in moderate heat (85 degrees) and fairly substantial long steep grades. I pulled the same route with the same trailer when the truck had app. 3 k on it but it was in the fall with cooler temps and to tell the truth I can not remember the operating temps. but I know they were not as high as I just experienced. The dealer is telling me that since the engine was creeping up to 235 degrees that this in turn was heating up the tranny, due to both cooling lines running thru the same radiator. I guess I will let them attempt the fix and take off and run the same route once the temps heat back up next year.

[Mark Rinker]

Was the fan clutch fully engaged continually during the high water temps? Anyone suggested testing its function?

[SoTxPollock]

Huntington, Mark is right. If the fan came on you would absolutely remember. They do roar.

[Hunnington]

Fan would come on when the engine temp went towards 235

[Bobo]

LLY's seem to have a problem with overheating. Your best bet is to keep up on your maintenance and log/document all your trips. Weigh the truck at a certified scale and keep the slip to prove your vehicle was not over weight when it overheated. Take pics and/or video of the trailer and rig, temp gauge, or any other signs of overheating. Presenting a good case to GM when dealing with the overheating will aid you in getting it fixed right or bought back. It will take you some time to do all this, but it will help you in the long run.

There are some mods that you can do to fix the problem. They cost about a grand and I doubt GM will pay for them. One is a radiator mod and the other one is a engine oil cooler. They both claim to stop LLY overheating.

[Onebigcanuck]

Mine was starting to run a little hotter in the 100F this summer. It hadn't in the previous year. I looked in the grille and found that 2 rows of the tranny cooler had been pushed close (self car wash??).

Once they were opened she ran a lot cooler.

Maybe have a look ???

[killerbee]

The dealer is telling me that since the engine was creeping up to 235 degrees that this in turn was heating up the tranny, due to both cooling lines running thru the same radiator. .

He was correct. The tranny would be better off in this case, bypassing the rad. Most of the time the radiator is heating (not cooling) the tranny fluid.