[GA_ZL1]

I had a GM tech do a ATF change recently on my 2023 ZLE A10 after the recommended 15 hours of track driving. The next time on track (yesterday at Road Atlanta--it was hot), I started getting some funky shifting, which makes me wonder if the bleed was done correctly. I wonder if there was too much ATF in the pan and hence I was getting overheating. According to this forum and a video recommended by ZL1 owners (https://youtu.be/dPrP4NQZg6w), the AFT should be between 203-212 F before removing the bleed plug. Is that correct? My car has the the OE tranny pan still in it, so I presume that the bleed post inside will give me the proper "track level" for ATF. Right? Does it make any difference what driving mode the car is in when the tech is bringing the fluid up to temp and doing the bleed? Should it be in "Track" mode? Anything else I should discuss with my tech to make sure the AFT was changed properly and the level is set properly for track driving? FYI, I drive in the Competitive Driving mode in Track at the "Sport 2" setting, which was the case yesterday. TIA!

[Vigilante375]

That video is correct on changing the fluid and making sure it's at the correct level. Bringing the transmission up to temp doesn't require a specific mode to be used. The car is just sitting there while it's being warmed up and not running thru the gears. The video explains that. You bleed it by pulling off the screw on the bleed port to let the excess fluid out until it stops then put the screw back in. Then it's properly level.

There's not really much to talk with the tech on this other than are they following the procedures correctly, are they letting it warm up to the correct temp and are they bleeding it correctly.

I don't know why GM is going this route with the transmission (well, to make it so that you have to come back to them for a fluid change) other than to make it a pain in the ass for us that like to work on our cars.

[20Bluezl1]

Originally Posted by GA_ZL1

I had a GM tech do a ATF change recently on my 2023 ZLE A10 after the recommended 15 hours of track driving. The next time on track (yesterday at Road Atlanta--it was hot), I started getting some funky shifting, which makes me wonder if the bleed was done correctly. I wonder if there was too much ATF in the pan and hence I was getting overheating. According to this forum and a video recommended by ZL1 owners (https://youtu.be/dPrP4NQZg6w), the AFT should be between 203-212 F before removing the bleed plug. Is that correct? My car has the the OE tranny pan still in it, so I presume that the bleed post inside will give me the proper "track level" for ATF. Right? Does it make any difference what driving mode the car is in when the tech is bringing the fluid up to temp and doing the bleed? Should it be in "Track" mode? Anything else I should discuss with my tech to make sure the AFT was changed properly and the level is set properly for track driving? FYI, I drive in the Competitive Driving mode in Track at the "Sport 2" setting, which was the case yesterday. TIA!

That's is exactly why I'm afraid to take my car to service especially at a chevy dealer. I bought a extra pan to have a bung welded-in sonits easily drained to replace the fluid and the filter.

[GA_ZL1]

Thanks for confirming. I just spoke with my tech (seasoned GM guy who works on ZL1s and Corvettes), and he said he followed the warm-up procedure. He said to bring it in and have him look at it. Not sure what's going on if it's not an overfill issue. Troubling. I traded my 2018 ZL1 1LE M6 for the 2023 A10 and am hoping I didn't make a mistake in getting the auto.

Originally Posted by Vigilante375

That video is correct on changing the fluid and making sure it's at the correct level. Bringing the transmission up to temp doesn't require a specific mode to be used. The car is just sitting there while it's being warmed up and not running thru the gears. The video explains that. You bleed it by pulling off the screw on the bleed port to let the excess fluid out until it stops then put the screw back in. Then it's properly level.

There's not really much to talk with the tech on this other than are they following the procedures correctly, are they letting it warm up to the correct temp and are they bleeding it correctly.

I don't know why GM is going this route with the transmission (well, to make it so that you have to come back to them for a fluid change) other than to make it a pain in the ass for us that like to work on our cars.

[CalgaryZL1]

This is why I made this pan, I can drain and measure what came out and simply put back what did come out. I just don’t have faith in anyone touching the transmission

[Stephen12ZL1]

fluid is definitely at the wrong level...just take out the check plug at temp (>200°F) with the engine running in park while the car is level. PITA and very difficult to do without a lift. It isn't impossible but be prepared to get a shower of fluid mess. Also it is HOT and it will burn from exhaust nearby and boiling fluid temps. Fluid at 180°F or whatever they used isn't hot enough and doesn't follow GM's protocol. I guarantee you they did not get the fluid hot enough prior to checking it.

[Stephen12ZL1]

I hate to sound arrogant but I have adjusted at least 3 different ZL1s tranny fluid level at VIR for exactly the same issue and erratic shifting. It didn't take much but they were all overfilled. The craziness immediately disappeared and they enjoyed the rest of their track time.

[taylorforschool@gmail.com]

Originally Posted by Stephen12ZL1

I hate to sound arrogant but I have adjusted at least 3 different ZL1s tranny fluid level at VIR for exactly the same issue and erratic shifting. It didn't take much but they were all overfilled. The craziness immediately disappeared and they enjoyed the rest of their track time.

Sounds like experience not arrogance and it’s where I would put my money

[GA_ZL1]

Originally Posted by GA_ZL1

I had a GM tech do a ATF change recently on my 2023 ZLE A10 after the recommended 15 hours of track driving. The next time on track (yesterday at Road Atlanta--it was hot), I started getting some funky shifting, which makes me wonder if the bleed was done correctly.....

I finally was able to get a hold of a PC and download the Cosworth software. The first screen shot shows data from an early PM session last Sunday at Rd Atlanta when I had the funky shifting. The second screen shot shows data from an early PM session at Rd Atlanta in April. Note: The April session had the original factory AFT fill; the May session was after my recent AFT drain and refill. Now, the ambient temps were different on the dates (mid/upper 70s in April; about 90 and more humid in May), so I don't know how valid comparisons can be, but clearly the maximum AFT was hotter this past weekend (244 degrees F vs. 225 degrees F) when I had shifting problems. Also max water temp was hotter (246 vs 225), as was the max oil temp (298 vs 286). Man, these cars with the A10 run hot! However, these data tell us nothing about the volume of AFT in the system. Given these data and caveats, perhaps someone has insight into the two sets of data? I tend to agree that the AFT was probably overfilled when changed between the two track dates. I'm going to take the car back and have the tech recheck the AFT and bleed off excess fluid. Does anyone know the target AFT temp one should try to achieve before doing the bleed? Is that in the 2023 ZL1 1LE Service Manual perhaps? Thanks for everyone's input and help!

[GA_ZL1]

Originally Posted by Stephen12ZL1

I hate to sound arrogant but I have adjusted at least 3 different ZL1s tranny fluid level at VIR for exactly the same issue and erratic shifting. It didn't take much but they were all overfilled. The craziness immediately disappeared and they enjoyed the rest of their track time.

Thanks. I'm actually bringing my ZL1 1LE A10 back to my tech tomorrow to check and bleed the ATF again. I wish I could get the fluid as hot for him as what it's like when I come off a 30-minute session at Road Atlanta! What do you suggest for a target "shop" ATF temp before doing another bleed? TIA

[Vigilante375]

Originally Posted by GA_ZL1

I finally was able to get a hold of a PC and download the Cosworth software. The first screen shot shows data from an early PM session last Sunday at Rd Atlanta when I had the funky shifting. The second screen shot shows data from an early PM session at Rd Atlanta in April. Note: The April session had the original factory AFT fill; the May session was after my recent AFT drain and refill. Now, the ambient temps were different on the dates (mid/upper 70s in April; about 90 and more humid in May), so I don't know how valid comparisons can be, but clearly the maximum AFT was hotter this past weekend (244 degrees F vs. 225 degrees F) when I had shifting problems. Also max water temp was hotter (246 vs 225), as was the max oil temp (298 vs 286). Man, these cars with the A10 run hot! However, these data tell us nothing about the volume of AFT in the system. Given these data and caveats, perhaps someone has insight into the two sets of data? I tend to agree that the AFT was probably overfilled when changed between the two track dates. I'm going to take the car back and have the tech recheck the AFT and bleed off excess fluid. Does anyone know the target AFT temp one should try to achieve before doing the bleed? Is that in the 2023 ZL1 1LE Service Manual perhaps? Thanks for everyone's input and help!

You're asking what the temp the ATF should be to properly bleed it?

It's talked about in the video and if your tech person is has the procedure to do this then they should know.

There is no difference in the fluid and maintenance in the A10 between a ZL1 with or without the 1LE package.

[Stephen12ZL1]

volume is tricky as ATF expands in the system as the temperature increases. This expansion causes the problems which would never materialize on the street. I have also found leaving the car in "D" on track allowing 20 extra upshift/downshift events can really spike the transmission temps. I know what the performance supplement says about this but the unnecessary shifting which often occurs at VIR led me to start paddling the shifts manually. For a 25 minute session in the heat this realy adds up as every shifting event makes the fluid temp soar. I will concede the tranny does a great job in "D" if you have a time trial and need a one or two lap hero moment. At VIR for instance (just in turn 1) the tranny will downshift into 3rd unnecessarily then immediately upshift into 4th to 5th. As you approach turn 3, it continues the same unnecessary behavior and rolls through the same logic. I can do this myself with half as many events holding 4th gear...you get the idea. Get a rhythm and try it to see if it makes any difference at your track. Also double check to make sure the techs used the proper ULV fluid and not "whatever is available". Be certain they didn't use HP or Dexron 6. Hope this helps and good luck!

[GA_ZL1]

Originally Posted by Stephen12ZL1

volume is tricky as ATF expands in the system as the temperature increases. This expansion causes the problems which would never materialize on the street. I have also found leaving the car in "D" on track allowing 20 extra upshift/downshift events can really spike the transmission temps. I know what the performance supplement says about this but the unnecessary shifting which often occurs at VIR led me to start paddling the shifts manually. For a 25 minute session in the heat this realy adds up as every shifting event makes the fluid temp soar. I will concede the tranny does a great job in "D" if you have a time trial and need a one or two lap hero moment. At VIR for instance (just in turn 1) the tranny will downshift into 3rd unnecessarily then immediately upshift into 4th to 5th. As you approach turn 3, it continues the same unnecessary behavior and rolls through the same logic. I can do this myself with half as many events holding 4th gear...you get the idea. Get a rhythm and try it to see if it makes any difference at your track. Also double check to make sure the techs used the proper ULV fluid and not "whatever is available". Be certain they didn't use HP or Dexron 6. Hope this helps and good luck!

Stephen: Thanks for your thoughtful reply. I also had wondered about paddle shifting myself, but with the supplement indicating we should leave it in "D," I figured I should follow their recommendation. What I liked about my former 2018 ZLE M6 (my current is a 2023 A10 ZLE) was that I could select the shift points, and this is appealing even with the A10. I also would rather not have the car stay in the 5500-6500 rev range as it does in "D," with all the extra shifts, for we have massive torque even at much lower revs. Less time at or near red line should help everything run a bit cooler. I'm at the dealership today to get things checked out, but maybe I'll try manual shifts at my next event. I imagine that I should be able to use 3-5 gears maximum at a track like Road Atlanta, so it's probably not too difficult to paddle shift. I have a couple of DCT cars that I shift manually (one has a 9 speed DCT--my 2017 NSX), but I still only need about 3 gears for manual shifting. Sorry for being long-winded. If you or anyone else has further suggestions, I'd appreciate them. I'm trying not to have regret about switching from the M6 to the A10. :-)