Guys,
I had great luck running 610 whp and no issues. added nitrous (800WhP ) and a suspect transmission tune and killed it in 4 passes at the strip. I have since had a few tuning issues and am back to stock for the time being. My friend ( procharged 840 whp)tore up his transmission and thought it was a bad tune . after taking it to a new tuner thinking it was residual damage he had a new trans put in. It is on the way out after 4 passes at a half mile event. Another friend of mine who drag races a whole lot tore up their first trans when everything was stock. put in a new one and tuned engine. failed pretty quick. her third trans is now on the way out (over800whp). I see a few of these big HP cars on the internet and they dont seem to shift exactly right either. Is anyone running over 800 WHP and having great luck. I mean out using the car . not just a few passes. I am trying to get a real feel for this. between 3 of us there have been 6 transmissions tore up. we all 3 beat on the cars pretty hard. really looking for real world feedback from individuals using their car the same way. debating whether to mod my car again.

Thanks Kevin

 

Running near 1000bhp a built "auto" trans is always the way to go vs stock.

 

I don't know if "A8 fail thread" is the most accurate when you have a suspect tune in there. Get the line pressures wrong for a second and a half and there goes the transmission.

That said, it'd be great to know what the mechanical limits of the A8 are. We've seen some 9 second passes, and the LMR cars are over 1000hp, so something's possible, but what mods and tune changes they're doing is no doubt proprietary!

 

Are you running a c7 z06 ? If so would you share who built your trans. I have not found anyone yet.

Thanks,

Kevin

 

I think title is very appropriate. I discuss stock cars trans failing and modified failing Trying to get real info from real users. I see the big hp cars as well. One of the shops with one of the baddest cars did my buddy's car and he broke his transmission. Not looking for opinions. Looking for facts from people running the hell out of modified A8 cars and what success are they having. I hope I get some good honest feedback.

Thanks,

Kevin

 

I agree with Dave since you are talking about failures from non-stock power levels which is NOT indicated in the thread title. How about a thread title, "Multiple instances of C7 exploding" which would be quite an attention magnet but the accompanying post would then clarify that the explosion in question is C7 foaming explosive compound and not the current generation of Corvette.

 

Yep to be fair. I'm a M7 guy but the 800 rwhp part and a tune is going to affect the durability of the A8 when the car comes with about 530 rwhp.

 

I don't see anything wrong with thread title or the info Kevin is seeking. I hope the thread garners facts that help him - and this community - understand what it takes to make reliable, durable power with the A8, and I wish him luck in this quest.

It would be helpful info for the whole community.

 

Same here.


The thread title isn't helpful.

 

I know of several transmissions that have failed with everything being stock. It's a weak link period. Why is everyone so concerned about what the thread is called. Do we have to be so politically correct . Still hoping for good accurate feedback. Somebody please share results good or bad. Stock or modified. Are there any transmission. Shops building something that can take a beating?

Thanks,

Kevin

 

I for one am following this thread. I have an A8 and car is in shop getting mods. I wont be abusing quite as much as OP but I'd like to know what to look for and what fails so I know what to look for during round 2 of mods.

 

If you were out beating on your car modded or not and buying transmissions at $ 5500.00 per pop I think you might feel different. Do you have an A8 C7 Z06 ? If so do you drag race or participate in high speed events. If so can you share with us how the car is holding up ? Any issues? I am wanting to take my car to the next level again but am trying to find out how do I do that with this trans. That's it . Nothing more. I have talked to speed shops that assure me with their tune it is no problem. Then my buddy loses a trans with that guys tune. I know there are risks involved with modding. I have thrown away $10k so far. Before I do more I am looking for good solid info. Not sure why you don't think this or the title is appropriate.

Thanks,

Kevin

 

Lucky - LOL - I do beat on this thing from time to time. They are a blast.

 

Running 800hp thru an A8 trans. not designed for it is probably asking for trouble IMO, but it's your car and you can do whatever you wish.
IMO, strengthening the internals is only way to avoid future problems...taking it out of spec with "tunes" will probably grenade the thing rather than helping matters.

Yup.

Not yet.

I will when I do.

I should explain...
The title gave me (and others) the impression the discussion would be about a STOCK setup, not a modified one.
Now, if title was something like, "A8 failure on a modded car," I would have instantly understood.
Sorry for the confusion and good luck.

 

There is quite a few local C7Zs with A8s making 700-800+rwhp and they are living fine...AMP has one making 1100 rwhp and running 9.30s@150 on a stock A8 and been 182 mph in the 1/2 mile, they also have one making 1200+ and been 8.98@151 on a stock trans, so far its still going. Not saying they will last forever but, lots of them are holding up.... and then on the flip side, I've seen a few bone stock cars with A8s fail, hell some fail coming home from the dealer on the first drive.

My point is, there is a lot moving parts, a lot of things can fail...Odds are, if they fail at 800, they would have failed at 600...(unless its blowing through clutches, then its straight up too much power)... But since no one is reporting WHAT is actually failing in them, no one knows the real cause...Was it too much power that made fail? or a 50 cent clip that fell out of the valve body? No one knows...

I'd be willing to bet the "hard parts" in the 8L90 is VERY strong...I bet the stuff that is "failing" are small, incidental parts that when they go, cause full inoperation.

Look at the 6l80/6l90 from the C6/CTSV, those things have proven to hold 700+ rwhp time after time after time. Sure some fail, some fail on stock cars also. That is a proven transmission, and I have a hard time believing GM built the 8L90 to be weaker, when they intended on using it in their strongest production car ever...


That being said....at 800+rwhp, in a 3700lb raceweight car, there are no guarantees the 8l90 will hold up...same thing for the 6l80 for that matter.

OP, what is failing in your trans? clutches? bands? hard parts?

9 times out of 10, a combination of the added power and a sketchy trans tune kills them, then the real kicker is finding someone that can build them right... THATS where the real problem comes in.... Seems like no aftermarket builder can keep a 6L80 together at over 700-800.... Stock trannies seem to last longer believe it or not.

My last experience was with my C5Z that I did an auto swap on, I used an RPM Transmissions Level 7 4L65. I made 850 rwhp, ran low 9s and put 8-9k miles on it, COUNTLESS 3-2-3 highway bombs...and that transmission was still as good when I sold the car as the day I put it in, but that was a $5k transmission also..

I'm sure it won't be long before people are doing 4l65 swaps on C7s if the A8s start dying often.

 

That may be.
However, it has been conventional wisdom for as far back as I can remember that when significantly more power is being put thru a drivetrain strengthening of the transaxle is preferred for the sake of longevity.

Drag strip runs put a lot of stress into the system.
I wouldn't want the anxiety while waiting for the Christmas Tree to cycle thru and wondering if I am few seconds away from buying a new trans.
Of course, YMMV.

 

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 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.

 

If I was going the Big Horsepower route with an A8, I would ship my car to Callaway or someone of equal reputation and expertise.
For me at least, it would take a lot worry out of the equation.

 

Sun,
I agree it is a worry free option. However a z06 with meth, tune, and headers will out perform the Callaway in a straight line. Never ran one on a road course so can't say. at these HP levels I never had any issues. In hindsight I should have stayed there but you get the speed bug. If any of the builders would offer up maybe a 700whp or more package with a drive train warranty I would take a hard look at it and I know a lot of people would. However I think until the after market people do something with the trans I don't think that will happen. I would hate to have to warranty these much over 600 whp.

Kevin