Transmission cooler

[newdude]

These 6L80/90 transmissions have low friction loss very low slip if any due to the clutch to clutch design. They run them hot for efficiency. Less friction, better mileage. Even the front drivers run 160-190 degrees.

 

The exception to this is the HD trucks and the GMT-900 and prior trucks. They are a constant flow (no thermal bypass preventing flow) through the radiator and aux if equipped. My 2012 ran no hotter than 170 in the summer and kept a consistent temp range of 120-150. Same for my 2015 HD. 120-150.

[HondaHawkGT]

I hit 205 several times in 80-90 deg weather this summer without towing anything.

[Brian S.]

I hit 205 several times in 80-90 deg weather this summer without towing anything.

 

I've hit 220 with my 4.3l one time while towing. GM tech support told me not to worry up to 230, and in a thread I posted about this issue a guy posted a response from them where they said 270 is where the fluid is damaged.

 

The shop I bought it at told me there is no OEM cooler as you found, and that I should not add one.

[XYZ]

The 2014 Sierra I was going to buy before it got sold out from under me listed an auxiliary trans cooler on the options, which was one of the reasons I wanted it.

[nando87]

I live in AZ and the summer is HOT, earlier this summer when towing my 23ft Toy Hauler up some decent grades my tranny temp would hit 250 on pretty much any long grade. If the grad was steep but short I would see about 220-230 regularly.

[Jon A]

http://www.carcraft.com/techarticles/116_0308_transmission_cooler_basics/?__federated=1

 

While my temps are technically in range, they are at the top of the range. That's cruising with no load.

 

Most of those charts and articles from companies who make transmission coolers are based on 1980's vintage testing. Different transmissions, different fluid. A chart with a newer transmission and Dexron VI might be informative, but I've never seen one. They claim Dexron VI is twice as resistant to oxidation so that would really change those charts.

 

I live in AZ and the summer is HOT, earlier this summer when towing my 23ft Toy Hauler up some decent grades my tranny temp would hit 250 on pretty much any long grade. If the grad was steep but short I would see about 220-230 regularly.

 

Yes, that's definitely hot enough you'd want to do something about it. As mentioned before, reprogramming the fans is the easiest, and if that's not enough an additional air-air cooler would help.

 

Something else that will help that's expensive, but there are a lot of other reasons you might want to do it anyway, is re-gearing. If a set of 4.10 gears lets you pull those hills in 3rd instead of 2nd gear, the transmission (as well as the engine) will tend to run much cooler.

[nando87]

 

Most of those charts and articles from companies who make transmission coolers are based on 1980's vintage testing. Different transmissions, different fluid. A chart with a newer transmission and Dexron VI might be informative, but I've never seen one. They claim Dexron VI is twice as resistant to oxidation so that would really change those charts.

 

 

Yes, that's definitely hot enough you'd want to do something about it. As mentioned before, reprogramming the fans is the easiest, and if that's not enough an additional air-air cooler would help.

 

Something else that will help that's expensive, but there are a lot of other reasons you might want to do it anyway, is re-gearing. If a set of 4.10 gears lets you pull those hills in 3rd instead of 2nd gear, the transmission (as well as the engine) will tend to run much cooler.

I won't tune my truck only because the fact that it does run so HOT, the last thing I need is for there to be something wrong down the road and it not be covered because I tried to help my issue.

[2018GMC]

 

Based upon what? There's absolutely no advantage to running colder transmission fluid except worse mileage. You aren't going to hurt the transmission unless it gets a lot hotter than that for extended periods of time.

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