So I need some advice here. I’ve been a long time lurker, first post. A little bit of info, I have a 2015 Tahoe LT 4x4 with the 6l80, I bought it with a bad converter and it was unable to move, the trans was shot. Long story short, I’ve rebuilt my 6L80 myself following nicks transmissions on YouTube. I’m fairly confident in the job that I did. Once I put it in and start driving, the temp goes up, but never comes down. So then I thought well I’ll put a thermostat bypass in it, it didn’t change anything, then I put the big 40k cooler on it, still no change. Maybe it takes it longer to heat up, but still doesn’t regulate at what a normal temperature should be. The upgrades i did were sonnax billet piston, transgo valve body shift kit, borg warner high energy frictions, superior solutions bypass, the cooler, I’m sure I’m forgetting more stuff. If anyone can shed an any insight, im all ears. Thanks!
Overheating 6L80e
- Thread starter Ryat242
- Start date
Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.
swathdiver
Full Access Member
exactly what "temps" are you seeing?
Did you replace the TEHCM? if so, did you program the new TEHCM to the vehicle...How hot is the temp getting? Temps shouldn't be above 200-215 F daily/normal street driving....
I do recall one of my builds got real hot very fast and the tech doing the install stopped right away and turned it around...The fix had something to do with the tune; some parameters that required adjustment...Sorry, I don't have the details but whatever the tuner adjusted, it worked and temps went down to 160-170isih and stayed there...
Okay. So I’m very glad you added that second part. Today when I tested it it got to like 190F fairly quickly. I then turned off and had the laptop with me and kind of went back through the tune that I had loaded, I didn’t really see any issues with it but I reloaded it to the truck on the side of the road (I was desperate lol) after I did that I started it up and it dropped to the 160-170ish range and when going through stop and go traffic it creeps up to 185ish but that’s the hottest it got after that. Now my question is, with a thermostat bypass and the big cooler I have installed, is 160-170F about what should be expected? I kind of thought it would be lower, but it’s definitely fluctuating now, which is something it wasn’t doing at first. **I also wanted to add that the weather today was 55 F
Now going back to the first question, no I didn’t replace the TEHCM, I bench tested it and it all looked good. So I just thought id roll the dice on it, I did rebuild the little screens on the TEHCM though.
Last edited:
So I never really saw a really high temp, I guess I was more concerned with the amount of time it took too get “warm,” if it was idling, it would slowly increase but if you drove it, it would shoot to 190F within 5 minutes or so, even when the temps outside were mid 30s. So I knew something wasn’t right, I also noticed that it never fluctuated, just kept increasing 2 degrees at a time rather steadily, no matter the speed or gear it was in. Once it jumped up to 190, I would turn around. I never saw it go over 215 id say.
@NickTransmissions i do want to give you a huge thank you for everything that you do on YouTube, you were a huge help! I have a hydraulic background, and have built several engines in the past but never a transmission, to say I was intimidated would be an understatement. Your videos made it make sense and gave me a great starting point to work from. I’ve recommended to all my buddies to watch your channel and give it a try themselves before taking theirs to a shop. I like knowing exactly what was replaced in a rebuild and a lot of the shops in my area I’ve talked to are very vague on what they actually replace. So a huge thank you!!
160-170 is ideal but Dex 6 can handle 200-215ish no problem so if you're consistently seeing 185ish and it stays that way throughout the summer months then it's fine. The 6L80 in my GMC Sierra doesn't get hotter than 175-180 which is perfect for most automatic transmissions. Keep an eye on the TEHCM, IMS and speed sensors if you didn't replace them...The IMS doesn't go bad very often but the other two do fail more frequently once mileage on them gets north of 200k...
You're welcome and thank you for watching my videos - appreciate the support and recs ! Congrats on your first rebuild.
With our thermostat deleted 15 suburban we just took a 2 hour road trip this past weekend with temps in the 20's and 30's transmission never went above 125. All highway driving. In the summer on a road trip, again all highway, it usually is around 140-148. It's the wife's so I only drive it on our road trips. City driving I don't have a clue since where we live and go I wouldn't call it "city" driving.
