A8 fail thread
Thread Starter
Pro
Joined: Jan 2015
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From: Trophy Club Texas
I suspect GM would have had an automatic transmission in their big HP cars for years if they thought they would hold up and be worth warranting. They didn't which cost them sales based on the popularity of the A8 in the Z06. So my guess is that there is something or several somethings in the A8 that are pretty much at their design limits at 650 hp. Add HP and things will happen more quickly than they will at stock levels.
I think you are correct. Thats the data I am looking for. I think up to about 600whp is pretty dependable on most cars. after that stuff starts breaking. not just z06. My buddys camaro did pretty good until he hit about 630 whp. spent a lot of time in the shop this year. seems to be a breaking point.
Kevin
Le Mans Master
Joined: May 2006
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From: League City Tx
Aj,
I agree that the failures seem to be all over the map. some big hp, some not so much. I have only replaced one so far. it was at the chevy dealer and never got a failure report other than it failed. Bought a new one and moved on. Assumed it was just a bad tune( it was) and did not give it another thought until my friend lost one this weekend after 4 passes at a half mile event. first time out with new trans. this was his 2nd to fail, first one by a bad shop, 2nd was done by one of the good shops. I know about the same 3 or 4 cars that seem to be working pretty well. i was trying to get a bigger look at whats going on out there. what kind of luck is the average guy pushing 800whp or so having. are the procharged cars doing better due to a less aggressive torque curve? just looking for data. I expect things to fail but some of these that are getting really used seem to be failing really quick. not saying a widespread issue at all. the few people I know personally that have these cars have had some trans issues. not all are tune related. Maybe I need a C5 or C6 with a built drive train. have been considering that for sure.
Thanks,
Kevin
I agree that the failures seem to be all over the map. some big hp, some not so much. I have only replaced one so far. it was at the chevy dealer and never got a failure report other than it failed. Bought a new one and moved on. Assumed it was just a bad tune( it was) and did not give it another thought until my friend lost one this weekend after 4 passes at a half mile event. first time out with new trans. this was his 2nd to fail, first one by a bad shop, 2nd was done by one of the good shops. I know about the same 3 or 4 cars that seem to be working pretty well. i was trying to get a bigger look at whats going on out there. what kind of luck is the average guy pushing 800whp or so having. are the procharged cars doing better due to a less aggressive torque curve? just looking for data. I expect things to fail but some of these that are getting really used seem to be failing really quick. not saying a widespread issue at all. the few people I know personally that have these cars have had some trans issues. not all are tune related. Maybe I need a C5 or C6 with a built drive train. have been considering that for sure.
Thanks,
Kevin
However..if you wanted to build something really fast and strong, especially for drag racing, I'd definitely stay away from the C5/C6 platforms...you can/will spend insane money trying to keep them alive on the drag strip, and still have them break, and still be at the mercy of "specialty" shops for transmissions and diffs...
That's exactly why I got rid of mine and bought the C7Z to cruise in. If I get the bug to go fast, I'll build an LS based Nova or Camaro with a turbo setup and real drive train for half the cost of building a vette.
But I digress...
As for the 8L90, I would definitely stay <700rwhp to maintain some reliability for piece of mind, and sadly I'll probably stay <600 myself to never worry about the trans..
I think for guys that want to build a FAST C7Z for the strip, you're gonna have to penny up the $20k for a 4L80...and even those are far from bulletproof.
Advanced
Joined: Mar 2016
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For what it’s worth: stock 2016 Z51 with 5k miles here and A8 still in shape even though I push her pretty hard. My A8 seems to be a bit out of tune. Up shifts into 2nd and 3rd come with a big punch, I wouldn’t be surprised if the trans goes out within warranty time. Just a feeling. Bought her in March. You guys know of any factory side A8 software updates?
If I’d throw cams or screws at it, I’d upgrade the trans right away, or more likely sell the car and get a M7.
If I’d throw cams or screws at it, I’d upgrade the trans right away, or more likely sell the car and get a M7.
Last edited by McCarthy; Oct 16, 2016 at 08:17 PM.
Safety Car
Joined: Nov 2011
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correct me if I wrong,but I would think it would be common sence that if you build a car to 800hp and or above and recalibrate the tranny or motor you should be smart enough not to depend on a stock tranny that was designed for 650 hp.and then complain if it blows.i am a common sence kind of guy and a old street racer.back then everybody who built their car put in a rock crusher tranny because we all knew and expected that stock tranny would not hold up to the abuse.and yes I know his is a auto and we all had sticks back then but the principal is still the same.build it and eventually if you beat it enough it will blow.if you want to go big you gotta pay,no way around it.
Race Director
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Thread Starter
Pro
Joined: Jan 2015
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From: Trophy Club Texas
correct me if I wrong,but I would think it would be common sence that if you build a car to 800hp and or above and recalibrate the tranny or motor you should be smart enough not to depend on a stock tranny that was designed for 650 hp.and then complain if it blows.i am a common sence kind of guy and a old street racer.back then everybody who built their car put in a rock crusher tranny because we all knew and expected that stock tranny would not hold up to the abuse.and yes I know his is a auto and we all had sticks back then but the principal is still the same.build it and eventually if you beat it enough it will blow.if you want to go big you gotta pay,no way around it.
Kevin
Le Mans Master
Joined: May 2006
Posts: 9,993
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From: League City Tx
Lord, I can assure you I am smart enough to understand this. I have not been successful in finding anyone that builds a stronger trans yet. I was hoping to see what luck other users where having. I had great luck at 600whp. Maybe some guys are having good luck at 700. I don't know. This is the purpose of this thread. I did not realize stating facts was necessarily complaining. Maybe I need a lawn chair and a windbreaker. That way I won't break my car anymore .
Kevin
Kevin
Hopefully someone will come to the market for a building a good 8L90 because there will definitely be a demand for it..
I wouldn't think building one would be THAT much different then building a 6L80, it seems the tuning aspect of it though is a whole different ball game.
I'm definitely sub'd for building/upgrading progress...
I'm also interested in the original point of this thread, lets see who is making 700-800+ with the A8 and what are the doing with it. Racing dyno charts and bragging at car shows or actually making hits.
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Thread Starter
Pro
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From: Trophy Club Texas
Yes sir Travis. I believe I see you signed up as well. We will be stock more or less but looking forward to it. Ill be the slowest guy there. But Ill be having fun. I hope we have a 40 mile an hour tailwind! Come find us. we have an old RV rented.
The Consigliere
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From: 2023 Z06 & 2010 ZR1
Safety Car
Joined: Nov 2011
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Lord, I can assure you I am smart enough to understand this. I have not been successful in finding anyone that builds a stronger trans yet. I was hoping to see what luck other users where having. I had great luck at 600whp. Maybe some guys are having good luck at 700. I don't know. This is the purpose of this thread. I did not realize stating facts was necessarily complaining. Maybe I need a lawn chair and a windbreaker. That way I won't break my car anymore .
Kevin
Kevin
