Acceptable Transmission Temp

[426ted]

Hey all. My '16 GMC developed a shudder at certain speeds at 112,000 km. I took it in and they replaced the fluid under warranty. The shudder is gone, but the transmission seems to be running 10-15 degrees Celsius higher. I was travelling through the mountains on the weekend and on one hill the temp was 92 degrees. The truck was empty other than the wife, kids and a bit of clothes. Outside temp was -5 C. Any thoughts if this could be an issue long term?

[durandetto]

From reading other, more knowledgeable people's posts on here, I'd say that it's definitely not great for long term health of your trans. Might want to look into the tstat mod or something similar to keep your temps a little lower. I'm sure someone wiser will chime in soon.

Sent from my SM-N975U using Tapatalk

[CamGTP]

Technically speaking, that is the ideal temp for fluid life. Having temps around 170-200º (78-93º C) should allow for fluid life up to 80-100k miles.

 

It's when temps exceed 215-230º (102-110º C) does the life of the fluid take a sharp turn downwards.

 

So what you are seeing running through the mountains is just fine. I was up at the cabin this past weekend and with temps around 15-20º (~ -7º C) coming home which is about 100 miles the temps were steady at 185º ( 85º C). That is where the factory thermostat in the cooler line wants the temps to stay.

 

The OP, it's up to you if you think something needs to be done.

[g2full]

Mine seems to live between 185-198º. I haven't worried about it to date. 

[426ted]

Good to know guys. I was just curious as I had never seen temps that high when towing in the summer on camping trips. I'll keep an eye on it.

[g2full]

I actually think there was one time I put it over 200 degrees. But I was grade braking with a load down 7 mountains here in PA, so to be expected. 

[flyingfool]

200-F is about the point where plastic , rubber o-ring components begin to dry out and degrade .. if you lease  the truck no problem. but at about 150-180k miles the trans will loose a lot of functional life if not need rebuilding. only doing short commutes will make it live longer. 

mine is at (135/150 F  city/highway) driving no t-stat

[Grumpy Bear]

Some data I've been collecting. Bottom axis is the air temperature. Vertical axis is the transmission fluid temperature. This graph is constructed with the transmission thermal bypass valve (thermostat) bypassed internally and lower radiator thermostat settings. You could add about 25 F to the fluid temperatures of the blue line with the factory 207F thermostat. 

 

Before modifications this transmission would run between 192F and 225 F air temperature dependent and I don't tow or haul much of anything. In the winter the transmission fluid temperatures would not reach the 192F stat setting for 100 miles of highway driving. If it was under 10 F it would take over 50 miles to reach the 104 F point. That is the lowest temp the trans tune/torque management tables allow 'normal' functionality. The factory stat hasn't a minimum flow bypass to warm the fluid. With the delete trans temperatures are up to the line in about 15 to 20 miles. 

 

 

This transmission also is equipped with the PML 8 quart pan and runs on a diet of Red Line D6 ATF. It's one of the nicest gearboxes I've ever experienced in 50 plus years of driving. For what that's worth. 

[Jacoby]

Your temps are fine OP. Nothing to worry about

[Ozer]

What about the opposite? I did the thermostat mod and my temp are anywhere from 92-112 now that its cold out.

Is this bad?

[Grumpy Bear]

56 minutes ago, Ozer said:

What about the opposite? I did the thermostat mod and my temp are anywhere from 92-112 now that its cold out.

Is this bad?

Like the 10 mile trip to work or even on a two hour drive? Winter and summer? Need more info. 

[Ozer]

1 hour ago, Grumpy Bear said:

Like the 10 mile trip to work or even on a two hour drive? Winter and summer? Need more info. 

Summer im around 145F average 

Winter so far I'm around 112F avg

 

I don't really take short trips, usually avg of 30 mins to work. 

[Grumpy Bear]

2 hours ago, Ozer said:

Summer im around 145F average 

Winter so far I'm around 112F avg

 

I don't really take short trips, usually avg of 30 mins to work. 

That's a little cooler than I run but I don't have the second cooler in the AC condenser. Anything under 180 F is my target. I've been thinking about a FIA radiator cover for winter. I've been using black duck tape the last few winters Over 104 F is sort of a rock bottom based on the TCM programing. I've also considered using an Improved Racing thermostat of 145 F to set a floor on the temp as it seems I have the top covered. So far, tape works fine. They have a minimum flow bypass, unlike the factory item, to help the heat up. But like I mentioned earlier when the 192F stat was still in use I could drive a very long time to get up over 104 F. Quicker now without it. Point is you have levers. I'd take 145 F over 225 F any day. 

[flyingfool]

for the cold seasons, it would be cool to bolt in active shutters from an LTZ truck or denali 

[Ozer]

On 11/13/2019 at 9:08 PM, Grumpy Bear said:

That's a little cooler than I run but I don't have the second cooler in the AC condenser. Anything under 180 F is my target. I've been thinking about a FIA radiator cover for winter. I've been using black duck tape the last few winters Over 104 F is sort of a rock bottom based on the TCM programing. I've also considered using an Improved Racing thermostat of 145 F to set a floor on the temp as it seems I have the top covered. So far, tape works fine. They have a minimum flow bypass, unlike the factory item, to help the heat up. But like I mentioned earlier when the 192F stat was still in use I could drive a very long time to get up over 104 F. Quicker now without it. Point is you have levers. I'd take 145 F over 225 F any day. 

Is it possible to cover part of the trans cooler to limit cooling on colder months? I need to see where it is and see if its possible. Or i may just leave it be, it runs fine lol