6L80 Heat Related Symptoms

[Charlie207]

No thermo valve on my 2013 and yes I have looked. Engine coolant temps are holding 210ºF with no variance. The trans temp worries me most as it will regularly get 15-20º hotter here by the depth of summer so if the 90-100º trend follows I'll be well into the hot end of DEX6 and the worst of the symptoms.
Best I know the radiator is original as it only has 117k miles (yes, it nuked the trans under prior ownership at less than 100k miles). A 40k cooler is in the cards for when I'm done rebuilding my friend's Nissan and can get my commuter car back and sideline the Yukon. The question becomes how deep does the hole go with rad, VB, TECHM, etc... to get this thing up to scratch for it's job or do I put an OEM HD cooler on it and trade this in for a 2007 2500 and skip the 6spd mess with a good old 4L80E.

The 6L80s are fine. Their issues come from the factory JMBX torque converter, which had a poor design. The back plate would warp over time, and the "hot spots" would shed their friction material into the fluid. This material would block critical ports, orifices, galleys, etc...

They aren't magically going to fail at 200F.

Switching to a billet-backed torque coverter would be cheap & smart insurance. Adding capacity to the fluid would also help, and there are external AT filter kits that are easy to adapt inline with the existing external/aux. coolers.

Understanding the underlying issue, first, then addressing it... that's how you solve a problem. For example: What is the max operation temperature of Dexron VI? It's wayyy more than 200F.

 

[donjetman]

250*f all day everyday is acceptable.
But change the atf at least every 50k miles.

 

[CTX-SLPR]

While DEX6 running that hot may be fine for the fluid, I have shifting issues when I get that hot. Just stacking a cooler on it to hold it down during normal driving only to have it act up when stressed while towing is not where I want to end up. I'm more interested in getting to the bottom of the shifting issues and looking for suggestions on stuff to test. I'm going to put the gauge back on it this weekend so I'll get a recheck of the pump health. If I'm going to drop the whole trans to do a TC I'm probably going to go through the guts as well since it's most of the hard work out done but I'd rather rule things out before getting there.

 

[Foggy]

Do you have factory (before tsb) transmission thermostat still in it? Lookup the tsb on it if you still do. And if you still do have the thermostat a bigger cooler won't do much it will just keep the temperature closer to the temperature the thermostat opens up at.

His year shouldn't have a trans cooler thermostat.. That's a 15 and up on These...
14 and up on the pickups

 

[15burban]

GMT900s (up to 2014) with the 6L80 don't have the stupid thermostat in the transmission cooler lines. It was added in the 2015s and up.

GMT900s (up to 2014) with the 6L80 don't have the stupid thermostat in the transmission cooler lines. It was added in the 2015s and up.

Sorry and thanks guys. I didn't see his model year til now.

 

[Doubeleive]

I was up to 200º within 45min of around town driving at ~85-90º ambient. I only have the factory radiator tank liquid to liquid cooler. The plan is to swap to OEM lines and a Tru-Cool 40K at some point but like I said, I'm quite worried about that just masking a deeper issue with heat generation that could leave me and the Scout trailer stranded.

if it takes 45 minutes for it to get that warmed up that's not all that bad or you just do not drive it that hard, before I added the tru-cool 40k and B&M deep pan I could have mine at 220 in about 5 minutes. now it tops out normally at 180, I can make it hit 190 if I push it in pretty hot weather light to light, anything beyond 190 takes something severe my version of severe is like trying to outrun the motorola block to block.
And if I drive like a sane person it stays anywhere from 145-165, hot idle in the summer is dead on 180

 

[CTX-SLPR]

Regardless I get shifting weirdness at around 195º. What are the likely culprits that start sticking with heat? Things are fine at lower temps like today a 1hr drive in the mid 50ºs and misting was fine with trans temps in the 140ºs. Yes, I'm a pretty relaxed driver but I bought this vs. a minivan because I need to tow and I can't keep it acting normal unloaded so no way I'm going to hitch something to it even with a 40k cooler in the nose. Something is getting hot and acting up and I'd rather try to troubleshoot it before thowing $3.5k at a reman Street Smart unit.

 

[Foggy]

Regardless I get shifting weirdness at around 195º. What are the likely culprits that start sticking with heat? Things are fine at lower temps like today a 1hr drive in the mid 50ºs and misting was fine with trans temps in the 140ºs. Yes, I'm a pretty relaxed driver but I bought this vs. a minivan because I need to tow and I can't keep it acting normal unloaded so no way I'm going to hitch something to it even with a 40k cooler in the nose. Something is getting hot and acting up and I'd rather try to troubleshoot it before thowing $3.5k at a reman Street Smart unit.

Have you put a real scanner on it to check your actual coolant temps under
differing circumstances ??
You may have a cooling issue, not a trans issue....
The gauge on the dash tells you absolutely Zero. It's a modified dummy light.
If your cooling system isn't up to *****, the trans will run hot

 

[CTX-SLPR]

Have you put a real scanner on it to check your actual coolant temps under
differing circumstances ??
You may have a cooling issue, not a trans issue....
The gauge on the dash tells you absolutely Zero. It's a modified dummy light.
If your cooling system isn't up to *****, the trans will run hot

Yes, put a scanner on it and checked the coolant and trans temps dash against the scan values and they were well within in the reading error on the needle and the trans was a fixed 4º offset between the DIC and the scanner. I'll put HPtuners back on it at some point to data log it again but from having a friend watch the scan tool in the passengers seat last fall things agreed pretty well.

 

[Foggy]

Yes, put a scanner on it and checked the coolant and trans temps dash against the scan values and they were well within in the reading error on the needle and the trans was a fixed 4º offset between the DIC and the scanner. I'll put HPtuners back on it at some point to data log it again but from having a friend watch the scan tool in the passengers seat last fall things agreed pretty well.

IF you have it already set up with HPT you should go thru your torque converter settings
and shift scheduling to get rid of some of the crazy crap gm did with those settings