Tranny Troubles

[DonnieB_1]

 

2008 2500HD 6.0 gasser with 6 speed tranny with M feature pulling a 29' fifth wheel. The trip through the mountains and back was relatively uneventful. The next day, the truck would not go into D. When it finally did, heated up to over 100C (212F) going 50 kph (30 mph). In no time the rpms shot up to 4K, and we were just crawling. Then no gear D or R would engage. I added a litre of ATF, and I could drive it to the dealer. Their computer showed no problems! The tranny guy (love that term!) said it only needed a flush and a new filter ($210). I suggested he was under-diagnosing it, and he said the computer indicates no trouble. Now, when the tranny fluid is cool, it barely goes into D, and runs very rough until the fluid warms. Then it seems to run normally.

What have I done to this poor tranny, how did I do it (used tow/haul almost exclusively in the big hills) and how can I get the dealer to look deeper than a simple fluid flush?

 

 

[gmtech4]

its under warranty still right ,5 yr ,

 

dealer is full of it ,go see another,i have no experience with the new 6 sp ,wish i can help but ,if it dont shift right,..... take it somewhere else