Overheating 6L80e

[Ryat242]

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.

So to go into a little deeper, I rebuilt the trans around 3 months ago, drove it and it was doing this issue then too. So that’s when I did the bypass and cooler, when it didn’t change I got worried I had installed a seal incorrectly or perhaps had knicked something when doing the install. So I bought another gasket/seal kit and tore it back open. Of course all the frictions and steels were in fine shape. I inspected everything and found nothing broken or installed incorrectly. Not knowing what the issue was, I just resealed it back up and here we are now. My question is, if something were bypassing causing heat is there anything in the valve body that could cause it? I made sure all the check balls were where they were supposed to be and torqued all the bolts to specs so I was confident in it, but now knowing all the seals are fine and nothings broken, its got me wondering. When I closed it back up this last time I didn’t touch the valvebody because I knew everything was correct. Have you ever seen that or heard of a valve body causing an issue like this? I have 2 spare core transmissions with good valvebodies in them, would it be worth it to rebuild one of those and stab it in?

 

[Geotrash]

So to go into a little deeper, I rebuilt the trans around 3 months ago, drove it and it was doing this issue then too. So that’s when I did the bypass and cooler, when it didn’t change I got worried I had installed a seal incorrectly or perhaps had knicked something when doing the install. So I bought another gasket/seal kit and tore it back open. Of course all the frictions and steels were in fine shape. I inspected everything and found nothing broken or installed incorrectly. Not knowing what the issue was, I just resealed it back up and here we are now. My question is, if something were bypassing causing heat is there anything in the valve body that could cause it? I made sure all the check balls were where they were supposed to be and torqued all the bolts to specs so I was confident in it, but now knowing all the seals are fine and nothings broken, its got me wondering. When I closed it back up this last time I didn’t touch the valvebody because I knew everything was correct. Have you ever seen that or heard of a valve body causing an issue like this? I have 2 spare core transmissions with good valvebodies in them, would it be worth it to rebuild one of those and stab it in?

Question: When you plumbed in the new cooler did you keep the oil-to-water cooler in the radiator end tank in the loop, or did you just go straight to the 40K? I'm asking because you'll see much higher temps without that radiator end tank in the loop. I know this first-hand.

 

[Ryat242]

Question: When you plumbed in the new cooler did you keep the oil-to-water cooler in the radiator end tank in the loop, or did you just go straight to the 40K? I'm asking because you'll see much higher temps without that radiator end tank in the loop. I know this first-hand.

I bypassed the radiator all together. Going straight from the trans to the cooler and back. Is that what you mean?

 

[NickTransmissions]

I bypassed the radiator all together. Going straight from the trans to the cooler and back. Is that what you mean?

That's the problem. Plumb it through the radiator then out to the aux cooler .

 

[Ryat242]

Uh

That's the problem. Plumb it through the radiator then out to the aux cooler .

What’s the thinking on this? Trust me I believe you guys. And I’ll try anything, is the fluid moving too fast to actually cool it? Or is the radiator cooler that efficient? I noticed yesterday that the faster you go, the quicker it builds heat. About a 20 minute interstate ride and the temps didn’t start to drop until i got off and went to a slower speed. And it cooled the best when it was sitting at a stop? Is this due to rpm and the thus making the fluid go faster through the aux cooler?

 

[Ryat242]

When I installed the cooler I couldn’t for the life of me find a video or thread taking about the best way to hook it up so I winged it. My thinking was that the trucks radiator sat at 210 once warm and I wanted the fluid to be cooler than that. Haha. Scientific I know.

 

[NickTransmissions]

Uh

What’s the thinking on this? Trust me I believe you guys. And I’ll try anything, is the fluid moving too fast to actually cool it? Or is the radiator cooler that efficient? I noticed yesterday that the faster you go, the quicker it builds heat. About a 20 minute interstate ride and the temps didn’t start to drop until i got off and went to a slower speed. And it cooled the best when it was sitting at a stop? Is this due to rpm and the thus making the fluid go faster through the aux cooler?

You're way over thinking this...Fluid is a much more efficient heat exchanger than air so by eliminating the fluid's travel through the radiator's internal transmission cooler, you've cut your cooling efficiency by at least 50% or so....