2015 2500HD Won't Go Into Overdrive

Winny56 · March 12, 2020

Hey everybody I'm new to the forum and need some help. 3 weeks ago I bought a 2015 Chevy 2500 with the 6.0l vortec with 96000 miles. Truck looked brand new.

Today after going about 150 miles at 70mph while pulling a 6x10 trailer the truck down shifted into 4th and wouldn't go back into overdrive. Transmission was running about 175°F. I rode like that for about 6 miles before getting to an exit. At the exit I stopped and killed the truck. When I took off again the problem had wenr away and the stuck was going into overdrive. After about another 10 miles it happened again and thus time a check engine light came on. During all this the transmission never shifted hard or funny, never seemed to not be getting power to wheels, it just simply wouldn't go past 4th gear. I had a 3 hour drive back home so I took the chance. I spent 2.5 hours on the Interstate doing 70mph at 2750rpm in 4th gear. Transmission temp ran a steady 183°F. Tranny never bucked or did anything out of the ordinary. I called 2 tranny shops on the way home and both wanted to talk about my torque converter going out. I truly don't believe that to be my problem.

Also forgot to mention that the trailer light plug-ins on the truck were still packed with di-electric grease and looked like they'd never been used. Could it be possible that the truck had never pulled a trailer before and the tranny control module was crapping itself trying to "learn" what was going on after never seeing that before?

Sorry for the long post but I wanted to make sure I give y'all all the details. I'll be headed to a shop in the morning for them to read the codes. Any help you guys could give would be greatly appreciated

Big Whiskey · March 17, 2020

Our trucks won't always hold 6th when towing at interstate speeds, but they'll usually hold 5th pretty easy. Mine would easily hold 5th (and sometimes 6th) pulling my small camper, 4-wheeler, etc. to Colorado and back, from Illinois. My dad's 6.0 will run in 4th a lot when towing, but his camper weighs just under 10,000 lbs. If yours was stuck in 4th with a small trailer, something is definitely wrong. The bright side is that yours threw a code, which should help diagnose the problem.

MNorby · March 19, 2020

Read code and report back

Winny56 · March 19, 2020

It is the torque converter guys. I can't remember the exact wording on the code but thats what it said. Also, after reading it, me and the tech got into the truck and took it for a spin with his computer hooked to it so he could watch the output on the TC. It was all over the place. But, they believe that I got lucky and we caught it early enough for it to not do any damage to the transmission. I'll find out in a week or so when the truck is ready for me to pick up.

They did say that they had never seen one do what mine did (putting it in limp home mode and throwing the code). They said that if I hadn't pulled that trailer that the problem probably wouldn't have showed up for another 20-30k miles and by then it would have been to late. I'll let you guys know how everything goes when I get it back.

jerseytaylor · March 23, 2020

my 6.0 threw a TC as well too. I feel like this was a recall back in the day for this configuration...dont quote me on that though.

Glasshole · April 28, 2020

Mine just went out too at 65000 miles. I took it to the dealer when it was still under warranty for erratic shifting. I was told all was well. Hopefully gm will still cover it

GTBensley · April 30, 2020

Any service history on fluid changes for people having TC issues? Just curious

fjtort2 · June 4, 2020

I’ve had 2 fluid changes on my tranny. 2015 6.0. I’m afraid my torque converter might be going out. Starting to bog under light acceleration and slipping into 2nd.