TT331FB

There must be an auxiliary tranny cooler then.

This is what doesn’t make sense…the tranny is cooled with engine jacket water. Cooling water comes off the engine is at 210. What comes off the radiator is about 180. I’m not sure how you can get the tranny any cooler than the average of (210+180)/2 or 195 which is what mine runs. A lower set Tstat would be open all the time but would not help cooling at all.

I had a 2003 GMC 8.1l w/allison 1000 that ran 210 degF. When I pull hills on the 2021, I have not seen higher than 200. I’m not concerned but I will look into your suggestion.

2021 6.6 Gasser towing 10,000# travel trailer. This trip, 2000 miles, getting average 9.6mpg. No oil use, 40% life yet to go and I haven’t added any oil sence the change. I’m very happy with this combination. We are traveling from Idaho to Florida. Tranny running 195 degF every time I look.

Use a clamp on DC amp meter at the wire coming off the circuit breaker to the trailer.

Low on charge. At idle refrigerant pressure drops until compressor kicks out. To verify, see if the compressor is turning when the suction line gets hot.

This truck was from Canada and was really low on fluid. I haven’t been able to go under the truck yet, one arm in a sling. My research found that extreme cold may cause excessive pressure and leaks. GM has a cold hose kit available for this. Any other insights? 2021 Silverado 3500 6.6 gas

I am posting this information in case this happens to you. I put about a gallon of DEF in the fuel tank. I was tired and my brain was not paying attention. Unscrewed the DEF filler, started the DEF pump, stuck in in the fuel tank, started pumping and then I woke up. I couldn’t believe what I had just done. Here is what to do to avoid serious problems. Don’t start the engine! To move the truck you will have to push the start button though. Don’t put your foot on the brake or it will start. FYI, hold the start for five seconds. It will turn green. Put you foot on the brake and shift to neutral. Here is the rub… when you turn on the ignition the tank fuel pump will prime moving the water through the filter and back to the tank. Once moved out you foot on the brake and shift back to park or better yet leave it in neutral to avoid moving water through the system more than you have too. Lesson #1 - to avoid fuel priming pushing water to the engine you will have to pull the fuel filter. This will make a big mess while the pump goes through it prime cycle, which I understand to be a timed interval of about 30 seconds. An option would be to disconnect the fuel filter feed hose instead of removing the filter. You may think that this is the solution to getting the DEF out but doing this still leaves DEF in the tank. The fuel tank must be pulled and flushed. This took about three hours at the diesel shop. Fill with a few gallons of clean fuel, change the fuel filter, and prime the fuel system five times. You will probably get a water in fuel service message. Drain the fuel filter using the inner 11/16 nut. Prime two more times and start the engine. Lesson #2- Carry a spare fuel filter and the wrenches to change it if you need to. You may run into bad fuel or repeat my dumb ass mistake. I was able to continue my trip the next day without problems.

I will use 5 gallons towing 7k# for 1000 miles.

No new transmissions available so GM remanufactured, new parts + old case I was told. I’m picking it up tomorrow and driving 13 hours home,. Tow haul active, trans temps normal before and after the failure.

Update: truck in the shop for three weeks now. No eta for the remanufactured transmission. I’m considering a lemon law claim.

43,000 miles.. pulling 6,000 # cruising at 63 MPH and getting 15 mpg. Heard an awful rattling sound and pulled over. Noice coming from the transmission. No service lights. Drive the truck to nearest dealer. They checked for codes and there were none. Dropped the pan and it was full of sparkles. They are replacing the transmission now. I have seen only one other similar post. The truck drove normally except with a new engine rpm wine and slow 8-9-10 shifts. Bummer