[GA_ZL1]

I (and others) have posted before about A10-equipped ZLE transmissions getting very hot at the track and then doing funky shifting/power cuts. I experienced this again at Road Atlanta last weekend in my 2023 ZLE, as per the first screen shot below (PDR data displayed using the GM Cosworth app). As you'll see, across this session, the trans temp went from 183 to 234, when shifting/power went haywire. The day was low 80s, which is not hot by RA standards. I've seen the AFT spike to as high as 244 with the same symptoms (see second screen shot from June 2023).

The problem, as diagnosed by others on the forum, is overfilled AFT. Before my recent event, I had my A10 serviced (GM says we should flush AFT every 15 track hours), and I explained to the tech that he needed to get the AFT temp at 200+ and then bleed off the excess fluid through the stand pipe. Perhaps he didn't get the fluid hot enough before the bleed. Maybe the AFT needs to be even hotter prior to the bleed?

Does anyone know of an ATLANTA AREA tech at either a GM store or an independent shop who is capable of setting the AFT level properly, so I can enjoy my car to its fullest on the track?

Also, two "solutions" have been offered in this forum. Any thoughts or suggestions regarding them?

1) Get the tranny nice and hot at the track and then bleed it off there. OK, but how does one do this without a lift and burning oneself with the hot car parts or hot AFT?

2) Shift in manual mode on track, to minimize the number of shifts and to control the RPMs (short-shift a bit). Interestingly, GM says one should NOT do this: "Manually shifting (aka tap-shifting) the 10-speed transmission during track events can lead to slower track times and may induce higher transmission temperatures" (as per Feb 2019 GM Bulletin No: 19-NA-038).

I had a 2018 ZLE with the 6-speed manual that I traded for my 2023 (I wanted to get a fresh ZLE before GM stopped producing them). I'm wondering if this wasn't a bad decision, for the M6 tranny never overheated on the track.

TIA for any advice of Atlanta area techs/shops or other suggestions.

Exasperated in Georgia.

[Slurpee]

I do not believe this is ATF temp related. This happened to me as well, check my post.
I am convinced this is engine oil temperature related. When you hit 300F on oil, the transmission starts to short shift to bring down oil temperatures. The short shifting goes away after oil goes below 300F. I confirmed the data in pi toolbox:
Your 298F max engine oil temperature supports this theory.
I believe the only remedy to this is to reduce engine oil temperatures, either by adding an air oil cooler, reducing your coolant ratio (I am trying 70/30 water/coolant with 1.5 bottles of water wetter), or managing your temperatures by introducing cooldown and hot laps. Our oil is cooled by our coolant. The hotter your coolant (246F is HOT), the hotter your oil will be. Putting the car in manual mode will not remove the short shifting. The car will still short shift before you touch the paddles. This will lead to double shifts, which I experienced.

The coolant ratio is the easiest. If I still have issues, I will try an 80/20 ratio before going down the air cooler option.

[Z OH 6]

Take it to Vengeance Racing in Cumming, GA.

[GA_ZL1]

Thanks, Slurpee, for the input! I always check my oil temp right after the checker flag on my cool-down lap, and even last weekend, the onboard gauge showed about 250-260 oil temp (it's tough to get a good estimated temp given our gauge does not show a digital output). And when I downloaded the data on Cosworth, I was surprised to see the oil 295 also. Yikes! Interestingly, I've never gotten a message or warning that either the tranny or oil temp were high. I'll check with my Camaro shop about oil temp being the culprit.

So, you're also saying that manual short-shifting isn't a possibly remedy? You say "Putting the car in manual mode will not remove the short shifting. The car will still short shift before you touch the paddles." It doesn't hold a gear until you use the paddle for an upshift? Were you manual shifting in your Road America video? Not quite clear about this.

Thanks again!

Originally Posted by Slurpee

I do not believe this is ATF temp related. This happened to me as well, check my post.
I am convinced this is engine oil temperature related. When you hit 300F on oil, the transmission starts to short shift to bring down oil temperatures. The short shifting goes away after oil goes below 300F. I confirmed the data in pi toolbox:
Your 298F max engine oil temperature supports this theory.
I believe the only remedy to this is to reduce engine oil temperatures, either by adding an air oil cooler, reducing your coolant ratio (I am trying 70/30 water/coolant with 1.5 bottles of water wetter), or managing your temperatures by introducing cooldown and hot laps. Our oil is cooled by our coolant. The hotter your coolant (246F is HOT), the hotter your oil will be. Putting the car in manual mode will not remove the short shifting. The car will still short shift before you touch the paddles. This will lead to double shifts, which I experienced.

The coolant ratio is the easiest. If I still have issues, I will try an 80/20 ratio before going down the air cooler option.

[Slurpee]

Originally Posted by GA_ZL1

So, you're also saying that manual short-shifting isn't a possibly remedy? You say "Putting the car in manual mode will not remove the short shifting. The car will still short shift before you touch the paddles." It doesn't hold a gear until you use the paddle for an upshift? Were you manual shifting in your Road America video? Not quite clear about this.
Thanks again!

Sorry for the confusion. If you put it in manual mode, the car will auto short shift without any driver input. It won’t hold the gear until redline.

Not in that video. I put it in manual mode after that. What happened is the car will auto shift upwards and then you will hit the paddle up shift anticipating redline. This is the double shift I was referencing.

I brought it to my dealer and they opened up a case with GM. They then ghosted me.

[Z OH 6]

Are there any other ZL1s with A10s at the track with the same issue?

[Gunkk]

I wonder how much EDIFF and exhaust heat contributes to the problem. Just a wag, but could it be contributing to a total thermal load issue on the trans fluid? On the subject, has anyone tried using down blowing pusher fans on top of the trans cooler? Or heat shielding on the ediff-to-trans fluid lines that run near the exhaust?

[Slurpee]

Originally Posted by Z OH 6

Are there any other ZL1s with A10s at the track with the same issue?

Yes. You can search on the forums there’s a good amount of documented cases.

[Slurpee]

Originally Posted by Gunkk

I wonder how much EDIFF and exhaust heat contributes to the problem. Just a wag, but could it be contributing to a total thermal load issue on the trans fluid? On the subject, has anyone tried using down blowing pusher fans on top of the trans cooler? Or heat shielding on the ediff-to-trans fluid lines that run near the exhaust?

Like I said, I do not believe this is trans fluid related. If you look at my video, I have this issue when the fluid is 226F, which is well within temperature specs.

[chevroletman]

This may not be related but I had issues with my 2019 ZL1 1LE getting hot - coolant 280ish and 300+ oil temps- car was completely stock. dealer tried to help, but couldn't duplicate problem, of course. dealer changed t-stat bled intercooler ect. same issues. I was lucky enough to have my PDR data from the 2017 ZL1 i had previous to compare with, showed dealer data from same track under same conditions. GM engineering and dealer were stumped ( car had only about 1500 miles on it at this time). long story short I determined that holding the engine at high RPM, above 5300 of so, for longer periods would cause temps to climb. So for example in a long sweeping turn with trans shifting on it's own and holding RPM at say 6000 temps would climb. Did some of my own testing and drove a mile down the highway holding RPM at 6000 no load on engine temps went up 15+ degrees on coolant in 1 mile at 60 mph. So I determined that coolant temp was RPM related. Dealer ended up changing the water pump and problem was solved. After my coolant temps stayed manageable around 225 trans is running cool and shifting issues are gone. Oil temps now stay around 260. Again sorry for the long post

[nighttowl]

Originally Posted by chevroletman

Dealer ended up changing the water pump and problem was solved. After my coolant temps stayed manageable around 225 trans is running cool and shifting issues are gone. Oil temps now stay around 260. Again sorry for the long post

Did they say what was wrong with the water pump?

[SpeZ]

Great to see I am not alone with that issue.
I tracked my ZL1 with 1LE aero recently.
My oil temp is really concerning, it was most of the time at 275° and after few rounds it even hit 290°. Used fresh 0W-40. Running at 840 HP at the engine.
I manually upshifted multiple times and in order to create less heat and give the the oil a chance to cool down a bit.
My trans temp was when I checked few times pretty much steady at 203°.
Even my freaking oil dipstick got cooked. It is literally yellow/gold coloured at the height where it sits next to the manifolds.
Everything exhaust related is stock, but I would bet going catless will noticeable decrease the oil temp.
Doing so will trigger DB limit at most tracks tho...

Edit: oh yea and coolant temp seemed to be always stable at ~203°. Once under heavy acceleration it went quick to 235°. Probably caused by extreme fast coolant exchange of the high revs.

[Slurpee]

Originally Posted by SpeZ

Great to see I am not alone with that issue.
I tracked my ZL1 with 1LE aero recently.
My oil temp is really concerning, it was most of the time at 275° and after few rounds it even hit 290°. Used fresh 0W-40. Running at 840 HP at the engine.
I manually upshifted multiple times and in order to create less heat and give the the oil a chance to cool down a bit.
My trans temp was when I checked few times pretty much steady at 203°.
Even my freaking oil dipstick got cooked. It is literally yellow/gold coloured at the height where it sits next to the manifolds.
Everything exhaust related is stock, but I would bet going catless will noticeable decrease the oil temp.
Doing so will trigger DB limit at most tracks tho...

Edit: oh yea and coolant temp seemed to be always stable at ~203°. Once under heavy acceleration it went quick to 235°. Probably caused by extreme fast coolant exchange of the high revs.

You may want to consider running 15W50 for the track with the added aero, especially if you are using stickier tires than OEM SC3s. My friend got in contact with M1 and their 15W50 doesn't degrade until a ridiculous temperature, something like 400-500F. I still do an oil change after every track event though, cheap insurance.

[mlee]

Originally Posted by Z OH 6

Are there any other ZL1s with A10s at the track with the same issue?

Yes, we saw this happen in 2017 at NCM with the regular ZL1