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Quick question for those with the A8 ZR1

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Quick question for those with the A8 ZR1

 
Old 02-20-2019, 08:09 AM
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bearphoto
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Default Quick question for those with the A8 ZR1

I'm contemplating trading in my Z06 A8 and my Z51 m7 for a ZR1 A8. Is this the same A8 trans the Z06 and other corvette models have that have occasional shudder issues or is this a beefed up or different trans built to handle the power of the ZR1? I have not seen any A8 trans issues from the ZR1 owners. Comments please. Thanks in advance.
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Old 02-20-2019, 12:43 PM
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Repo Pilot
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According to my dealer who sells alot of corvettes, the latest fluid drain and change (to a new fluid which will not suspend water) has solved it. GM also now has a way of hooking up their test software on a lap-top during a test drive that displays the line pressures in the A8. When it shudders it clearly shows in reoccurring pressure spikes.

I have a very small shudder at times under gentle acceleration which does show on the analysis but is nothing like what a problem car looks like. My shudder (in #1407) when it happens under low to moderate power, is barely noticeable and is gone almost as fast as it appears. I've never had a car with at AT in my life before the ZR. The shifts are lightening fast and solid. Even while in "D"umb mode you can instantly override the current gear selection with the paddle shifters.

The only bitch I have is that the Torque converter pretty much releases below 3000 during engine braking and I understand there is a setting somewhere in the performance menu to stop this from happening, I just have not had the time to find it yet.

BTW - the A8 has had no effect on my testosterone levels.

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Old 02-20-2019, 02:06 PM
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Hib Halverson
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Originally Posted by bearphoto View Post
I'm contemplating trading in my Z06 A8 and my Z51 m7 for a ZR1 A8. Is this the same A8 trans the Z06 and other corvette models have that have occasional shudder issues or is this a beefed up or different trans built to handle the power of the ZR1? I have not seen any A8 trans issues from the ZR1 owners. Comments please. Thanks in advance.
The C7s all use the 8L90. There are slightly different versions and different trans calibrations but all the A8s are basically the same.

The early A8s had a problem with shudder/chatter at certain speeds and RPMs but most of that issue was caused by the original formulation of Dexron HP automatic transmission fluid and how it interacted with the torque converter clutch. The formulation was revised, but then the revised ACDelco version of that fluid became difficult to source. GM then told its dealers to use Mobil 1 "Synthetic LV ATF HP". My understanding is that solved the chatter issue. All the A8s in ZR-1s were manufactured after that change was implemented, so I will be surprised if anyone with one of those cars has an issue.

I should add that I have a 8L45 in a 2018 Chevy Colorado. The 8L45 which is very much like the 8L90 but with smaller diameter rotating parts and a lower input torque rating. The early 8L45s, also, had the chatter problem. My 8L45 was factory filled with the newer fluid formulation and I have not experienced and sudder/chatter issues in the 5000 miles I've put on it so far.

Last edited by Hib Halverson; 02-20-2019 at 03:08 PM.
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Old 02-20-2019, 02:08 PM
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as repo pilot mentioned, the reason the zr1 are not having issues is because they are all 2019 model year, and that was after GM started using the correct fluid from the factory. The trans is not the problem, the bad fluid being used is what caused the damages and shudder on the earlier years.

You would have the same success with a 2019 z06 or grand sport or base stingray for that matter.
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Old 02-20-2019, 07:18 PM
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Excellent responses, thank you very much. My 17 Z06 has had no issues either with the A8 but its only used in M mode.
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Old 02-21-2019, 04:32 AM
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i have a 16 that im about to trade in, it has over 20,000 miles, and I have had no issue. Never did the flush. I drive the thing pretty hard. I don't do drag racing from a dig. That is probably what hurts it the quickest. If i was going to keep the car, i would get the flush done.
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