How hot is too hot for ATF?

[K20FA5]

My wife’s XT6 had a horrible shuddering problem. The dealer ended up replacing the torque converter and all of the valves in the 9T50. I assume that the torque converter died and sent crud through the valves. I never really paid attention to the temps before the repairs, but now it seems to run between 210 and 220 when cruising on the highway and in stop and go traffic. I’m concerned that some of the crud is also blocking the lines going to the radiator transmission cooler, or the cooler itself. There are no codes when I scan it, but I’m not sure if there would be? I’m trying to decide if it needs to go back to the dealer…

 

[Chris142]

I was always told not to go over 200. But the truck I drive at work goes to 230 often but the needle is still.in the middle of the safe zone

 

[Rand]

probably depends on where you are getting the temp. pan temp 220 or somewhere hotter.

 

[Oro_O]

You need to figure out where that temp is measured, and also maybe ask on a model-specific forum what others are seeing.

I have a temp sender in the pump area of one transmission. I see temps vary greatly between cruising and stop/go. A sensor elsewhere won’t vary as much, or could show much higher than average.

 

[jetman]

IIRC >270*F for a long period of time if it's a top tier synthetic.
My go to guy on ATF is Tom Johnson of JG Lubricant Services, retired GM/Allison fluids engineer.

 

[ripcord]

210 or 220 is right where GM intends for it to be. It's matching the coolant temps. Modern Dexron VI is way less heat sensitive than the old Dexron III fluid which started to oxidize over 180.

 

[The motor guy]

Had mine at 260 once for about 5 minutes then shut it off

 

[Lubener]

210-220 degrees seems very reasonable for your Texas heat driving on the freeway. Remember the fluid is being cooled in the radiator where coolant temperatures are around 200 + degrees.

 

[MSCH]

on just about any vehicle with an automatic transmission that has an torque converter clutch the torque converter clutch is applied when running on the highway, if tranny is running in the 200's ( even in the Texas heat) it probably has some issues.. most auto' tranny's if sustained temps of 250F or more are seen, the tranny is either cooked or on its way to well done. only time you see high temps might be in stop and go traffic where the torque converter is being a torque converter and you have low air flow over the cooler, other than that 200F or lower is normal.

Since you said tranny was shuddering, if its under warranty you probably need to get it on record..

if it isn't under warranty you need to find out what is going on. You might try changing the fluid and filter and adding some Shudder Fix..

https://www.amazon.com/dp/B0002JMLQU?ref_=cm_sw_r_apan_dp_0W7CA5V3K21WS49JXEYM&fbclid=IwAR1LU9OGh1UNV4buTtnFAEvoIMLbx7RX6_cd0FVpL6ffbvMwOtb0gl9LA9U&th=1

 

[CarDoc66]

Most late model GM cars with a few miles on them have black fluid when I check them. I mean low miles too, 20-30K. Years ago I was told the red dye in the fluid was there to tell you if it had been overheated. There must be a fluid temp warning lamp in that Caddy, chk your owners manual sometimes they have the information as to what temp will set off the light.
My Chrysler Hemi with the Mercedes NAG transmission never goes above 175 degrees when driving normal. I've seen 200-220 at the track when I abuse the torque converter but that's it. The trans and converter is completely stock using an external cooler integrated into the AC condensor and with a thermostatic bypass in the lines.
All the more reason to change the fluid every 60K or so.

 

[350Rocket]

My 4L60E will get as high as 210 in hot stop and go driving. Normally lower than 170 during my normal driving though. I didn't have access to the temps (through torque pro) before I got an auxiliary cooler installed.

 

[The motor guy]

Had mine at 260 once for about 5 minutes then shut it off

Transmission was in full blown 4th gear limp mode, before it was only partial limp mode. I didn't realize that at 190 it goes into full limp mode, so in about a mile it went from 190-260

 

[oilstudent24]

My wife’s XT6 had a horrible shuddering problem. The dealer ended up replacing the torque converter and all of the valves in the 9T50. I assume that the torque converter died and sent crud through the valves. I never really paid attention to the temps before the repairs, but now it seems to run between 210 and 220 when cruising on the highway and in stop and go traffic. I’m concerned that some of the crud is also blocking the lines going to the radiator transmission cooler, or the cooler itself. There are no codes when I scan it, but I’m not sure if there would be? I’m trying to decide if it needs to go back to the dealer…

Different vehicle of course, but my 2014 F150 runs around 200 degrees or so according to the digital readout. These are highway speeds and not towing. I don’t tow much to tell you those temps.

 

[The motor guy]

Transmission was in full blown 4th gear limp mode, before it was only partial limp mode. I didn't realize that at 190 it goes into full limp mode, so in about a mile it went from 190-260

My 68rfe had never been over 160 50-60 over ambient is about normal for it