10L80 - filled transmission at wrong temp???

[jyi786]

Update #2: Changed the transmission mount and this time, followed the procedure according to Alldata to properly check fill level.

With the truck completely off and the transmission cold, I just wanted to chance it and see exactly how much fluid would come out, if any, if I opened the check plug. According to the manual, it's supposed to come gushing out. Well, nothing came out. So I proceeded to pump the transmission with 3 quarts of fresh ULV ATF (I actually bought the special GM adapter that lets you attach it to the check plug hole), then set about raising the transmission fluid temp to 212F, which is what the Alldata procedure called for.

When I got the transmission to 212F, I then opened the check plug, and voila: fluid gushed out. About 2.25 quarts came out before it slowed to a steady fast drip, at which point I closed it and buttoned everything up.

I know that there is a difference between how much fluid was actually in there when cold vs hot, so I'm not exactly sure that even though I put in 3 quarts, the difference that came out was actually what was missing from the transmission: about .75 quarts.

Is being low .75 quarts enough to cause the 10L80 transmission to shudder? My test drive seemed to indicate that everything was good, but I will only be able to tell tomorrow when the transmission is cold.

 

[Seamus]

I did the same change a few weeks ago and used the check plug not the tube and did it at 167 degrees, maybe a little hotter. But not 212. I have not one issue. I doubt the .75 caused a shudder. How many miles on your truck? The 10 speeds have been very robust compared to 8 speeds that had the shudder from TC. I do know someone with a 2020 10 speed that had a TC fail at 45K. Unusual.

 

[jyi786]

I did the same change a few weeks ago and used the check plug not the tube and did it at 167 degrees, maybe a little hotter. But not 212. I have not one issue. I doubt the .75 caused a shudder. How many miles on your truck? The 10 speeds have been very robust compared to 8 speeds that had the shudder from TC. I do know someone with a 2020 10 speed that had a TC fail at 45K. Unusual.

I initially did it at 167F as well. I learned that it was wrong. My truck has 117K miles.

 

[BlaineBug]

For those with transmission cooler bypass and/or the revised transmission cooler thermostat, how are you guys getting it all of the way up to 212 degrees Fahrenheit? That seems way hot.

 

[jyi786]

Power torquing did the job for me yesterday in getting it up to temp. Took a while though.

And I drove it today. Shudders much less, but still slightly there, and only when transmission is cold.

 

[BlaineBug]

Power torquing did the job for me yesterday in getting it up to temp. Took a while though.

And I drove it today. Shudders much less, but still slightly there, and only when transmission is cold.

If you have the capability to buy or borrow a scan tool which can show you torque converter slip speed you may want to check and see what is going on simultaneously as you experience the shudder.

 

[Seamus]

Wouldnt it expand more at a hotter temperature?? Meaning at 167 and dripping out its overfilled-- not underfilled because it needs to fully expand at 212 then let it out plug. When it cools it will be underfilled and not come out the drain plug because its not expanded. It will only come out the plug at that temp and be correct.
I like science but hotter expands more not less. Cold contracts.

In essence I may be slightly overfilled at 167 not underfilled.

Thoughts

 

[Seamus]

To prove this theory I may drive my truck up on the lift hot, get it to 212 and i bet a little comes out the plug....and then this will be correct.

 

[jyi786]

Whatever the case may be, Alldata called for it at 212F, so that's what I did. I know that by doing it at 167F potentially introduced this issue, as I never had it before.

 

[15burban]

What does your trans temp normally run at? I'm still trying to wrap my head around why they would want you to check it at such a higher temperature then what it normally runs at. Since I'm assuming it's normal temp is below 212.