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Transmission Temp

3K views 31 replies 15 participants last post by  mwilliamshs 
#1 ·
I’m new to towing, so this is a weak topic, but I’ve been searching and finding tons of different information.

I’m towing about 3,000lbs. with a 5.3l Tahoe. Transmission temperature this past weekend reached 217, when I was crawling along mountain roads in WV. The typical temperature heading down was about 170-190 changing with terrain.

On the way home it pretty much maintained 163 degrees.

My main concern is, is there a temp that is dangerously low for a DD? I want to install a trans cooler to help with slower towing up those mountains, but am finding all types of stuff online for low temps for transmissions.

We’re towing out to SD this summer and I’m dreading Chicago. I know it’s going to tax that transmission if I don’t add a cooler.

If it matters, this is the 6 speed, with 120,000 on the clock.

Thanks.
 
#5 ·
Yes and yes, and I don't know how accurate they are. Probably not very.

It's really hard to over cool a transmission once it gets up to temperature. Getting it up to temperature is why it is recommended to run it through the factory radiator cooler first, then into an auxilary cooler. Down here in Texas where cold is a myth I run all my coolers straight and bypass the radiator, never had an issue, I do it mostly because I don't want anything else pulling cooling capacity from my radiator not because of fear it heating up the trans fluid too much before the aux cooler.
That makes sense. I just know sometimes in the winter my truck's transmission temp is pretty low, even driving 20-30 miles. But it was really nice towing, because it never went over 170.
 
#4 ·
It's really hard to over cool a transmission once it gets up to temperature. Getting it up to temperature is why it is recommended to run it through the factory radiator cooler first, then into an auxilary cooler. Down here in Texas where cold is a myth I run all my coolers straight and bypass the radiator, never had an issue, I do it mostly because I don't want anything else pulling cooling capacity from my radiator not because of fear it heating up the trans fluid too much before the aux cooler.
 
#7 · (Edited)
I run 4 stage tranny cooling. 2 stacked plate coolers 2nd with temp controlled fan & 2 thermal bypass valves first right at tranny for warm up and 2nd between coolers, external filter on return. Does not run through rad. Been 9 years & has 400k on it, all it does is tow. Max temp ever seen flogging it 205f internal and 195f in pan.

http://www.improvedracing.com/oil-t...sion-differential-fluid-thermostat-p-423.html

https://www.magnefinefilters.com/Magnefine-1-2-Magnetic-Inline-Transmission-Filter-R012M.htm
 
#10 ·
i had an 05 tahoe with the 5.3 and used a scangauge with it.

Transmission in that was always 100+ ambient air when it was warm. it was uncanny how dead on it was.... got it to 225 a time or two from heavy long climbs (think 9% for 5+ miles with 7500 pounds behind it)

My new expedition shifts so many thousands of times better and that thing sits at 200F no matter what its doing no matter how hot or cold it is...
 
#16 · (Edited)
That's interesting, and I had thought of that before the trip, so I did add a qt. to the fluid. It was between the add and full line, and had a bubble on the dipstick. One quart eliminated that issue.

I'm going to have to look up where to re-route this exhaust to, and add a deeper trans pan. I have no idea why they tucked these exhausts right under the pan. It's a pain in the arse, though. Running true duals would be nice, but the driver's side of this Tahoe is packed full of stuff, and I'm not sure I want a pipe hanging below the cross member.

EDIT: Never mind, I see they make deep pans for stock exhaust locations. Sweet.
 
#18 ·
I know we're talking about a Chevy transmission here, and I'm kinda guessing a 6L80. But on the ambient +100 deg thing--doesn't it depend on the transmission make? I've never seen the 6L90 in my pickup over 200, and rarely over 180.

But the 6R140 in my small motorhome is almost always 210-220, towing or not. A bunch of people here told me that was normal for a 6R140, and to not sweat it...

Obviously we're talking about very different use cases. I just wanted to see if that ambient + 100* thing was supposed to be universal.
 
#22 ·
There's a lot of information here I didn't know. I'm glad I asked. This is usually my go-to-forum for people who know their shit about shit. :smokin:

Anyways, I remember Beat95YJ talking about a deeper tans pan on his Tahoe. It's definitely an upgrade I'm going to do. Might also wrap the exhaust in some heat tape to keep it cooler around the trans pan.

The more fluid makes sense if you think about it. Just think of it in terms of a stock set up not pulling. If the trans fluid is too low, it heats up, and that's when you pull the stick and find bubbles all over it. Fill her full, and it comes out nice and perfect. Probably because, like ActionFab said, it's more fluid in the system, so it allows a great cooling time for the fluid laying in the pan.

The other nice thing about the deeper pan is that it puts into more fresh air flow, rather than taking all the heat off the motor.
 
#24 ·
Got another newb question: when adding an aux cooler, do you splice into the upper or lower line? I was watching e-trailer.com videos, and they said the upper line is considered the return line, but diagrams I'm finding online say the lower line is the return/cool line.

Anyone know for certain which is which on these 6-speeds?
 
#25 · (Edited)
The aux trans cooler stock is mounted right behind the grille. Can’t miss it. If its not there then that is you issue. Its lacking the tow cooler. Google gmt900 trans cooler install and read if yours isa 2007-2014.

You want the aux external cooler inline after the rad trans cooler. So rad trans cooler cools fluid first then aux cooler then to trans. This is how its done stock. This prevents over cooling.

Wrapping exhaust is retarded will rust your pipes way quicker.

The tahoe is 2005 newer is efans stock no fan clutch.
 
#27 · (Edited)
Just buy the factory aux trans cooler lines they bolt right up, then add aftermarket cooler behind grille and enjoy. Only lines to modify are at cooler mount behind grille and routing is stock. You can buy the line for $30ish bucks on line. Search on gmpartsdirect.com for part numbers then buy of Amazon. You want the aux trans cooler lines. Or use the stock kit GM P/N 19244188. Its the whole kit $110 on amazon.

Stock routes fluid from trans to rad cooler than to aux cooler then return to trans. This gets coolant up to temp quicker then cools it lower than rad temp when its hot out.

Also have tou ever changed the fluid before? If 120k and never been changed that doesn’t help.
 
#29 · (Edited)
Gm default config to turn on the electric fans is 230 degrees, engine temp.

Adding more fluid is never a bad thing. I put deep trans pans on everything.

I also like the trans cooler on it's own circuit.

But crawling around doesn't provide the air flow and the ECM isn't commanding fans until the engine heats up. So either change the fan setting or add more heat soak capacity, because the oil cooler itself isn't going to get air.
 
#30 · (Edited)
I installed the aux cooler. The normal operating temp unloaded has decreased significantly. Next on the list is a deep trans pan. As of right now after driving an hour in about 78 degree weather, my trans stays right around 127 degrees.

Honestly, I've never been good with vehicle wiring, so I can't say I'm knowledgable enough to install another fan, or mess with the factory wiring.

This Saturday I'm towing the SXS up north, which will be slower speeds on slight grades. I want to see how it handles that, and hopefully the temps are hot enough to test it. Seems like it's going to be a cold summer in the east.
 
#31 ·
You don’t need another fan. And with coolant ran to engine radiator it will help the trans warm up quicker in winter cold fluid is just as bad as hot. One reason why gm runs coolant to rad first then aux cooler. If you’re above 30mph you’re getting plenty of air flow this is a tow rig not rick crawler.
 
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