SHPirate

My 2015 C7 with 11k miles has a very slight shudder at 1500rpm, between 45-55mph. The car is out of warranty so rather than sticking the crappy GM replacement Converter back in I'm considering an after market from Circle D specialties. They offer some really nice heavy duty options. From what I have been told by a few transmission specialist is that the 8L90 (8 speed auto) is a very robust tranny and the only real issue is the stock GM torque converter.

My Corvette is a daily driver for my wife and she really doesn't want the
driving characteristics to change much. I play with the car on the weekends but
most importantly to me is durability. I would like my transmission to last
the next 100,000 miles without the further need for repairs.

That being said it looks like the lowest stall Circle D has to offer is around
2600. Will that be a noticeable change? Will this amount of stall make it
difficult for my wife to handle the car in the rain?

I'm curious what the stock stall is on the GM torque converter?

Any input will be appreciated.

Flame Red

My theory is that the aftermarket will solve GM's A8 problem. But unless you are a super tech with a full shop, R&R of a C7 torque converter is daunting to do yourself. I am sure a dealer would want thousands in labor to swap it out. So kind of expensive to be the guinea pig. Plus it would take many tens of thousands of miles to test if it really solved it.

I am kind of suprised one of these aftermarket manufacturer's have not tried it. There are tons on GM products that have this problem and it would be a huge market I would think if one really could solve it.

But the rest of us forum members would be grateful for your findings!

robert miller

You are correct on the circle D set up at 2600 stall. If you are not going to be racing this car with a really good size cam in it the 2600 will work in this car. The c7 converter is diff than the c5 & c6 the way it wk it is a triple disk so it will handle more rpm in lower range over the c5 r c6 converter. Your wife will not be able to tell the diff in that 2600 stall.

Joshinator99

sevinn

0'ing out slip tables is solution to the shudder and can save the factory converter if you catch it early enough.

BuLion

Robert, maybe you are right here; my only experience is I have a Precision 3000 stall on my 5th gen Camaro and compared to factory converter (~1800 lockup) its very different in driving behavior - for the better. The higher stall allows the engine to maintain the higher power band over a wider range.

This is one of the mods I've been considering on our Z next year as well, harden it up (over factory) and I kinda expect it to be "similar" to our Camaro in how it keeps the engine more in the power band.

SHPirate

Well after much thought and research I've decided to be proactive and even though my shudder is minor now I'm going to replace the torque converter.

Every single transmission guy I spoke with said a fluid flush is just a band aid that is covering up a damaged torque converter. The flush may work short term but on a high horsepower car like a Corvette the issues will return sooner rather than later.

I'm going to have a Circle D 265mm Pro Series billet (3 disk lock up) torque converter with 2600 stall installed. I'm luckier than most due to the fact my friend builds and drives dragsters and has a lift in his shop. He is very familiar with the Corvette 8L90 transmission. He figures we should be able to change it out in 6-8 hours. He is also very familiar with the GM LS motor so we will be doing a mild tune. He says the torque converter along with the tune will totally wake this car up without effecting the street drivability. Although the 460hp Corvette is already impressive, my buddy says that with this setup the car will be a street beast.

I placed my order with Circle D and because they custom build their converters it can take up to 10 days. I have been told by numerous transmission guys that the Corvette 8 speed auto trans is very strong and with the proper torque converter can withstand 700-800+hp engines.

I'm very much looking forward to having this work done and putting my shuddering transmission worries behind me. I will definitely check back in to tell you guys the outcome of my endeavor.

Wish me luck! LOL

lakemg

Keep us posted on the progress. Might do the same thing if my TC starts acting up

Mike Jesse

SHPirate

I have a guy that will be doing a mild tune on the car and he is also planning to adjust the shift points. He is a GM technician that helps my buddy work on his LS drag cars.

--My main objective is to remedy the torque converter issue and create a bullet proof transmission.

******It is VERY important that while doing these modifications I do not ruin the overall driving experience for my wife who drives the car everyday.******

--If while doing these mods I can make the car a little more peppy without changing the drive-ability it will be an added bonus for my weekend playtime!

At 460hp and with it's advanced suspension the C7 Z51 is already a street beast but I've been assured by the guys at Circle D, RPM Transmissions and my buddy, with this torque converter and a mild tune we can wake up this car without loosing it's smooth easy driving manners. I hope they are right because I'll never hear the end of it if the wife thinks I've made the car "too aggressive" LOL.

robert miller

I know, only reason I know this was when I called & was talking to the guy at CIRCLE D on the converter in what they do & have over the factor converter. He told me the stock set up was also triple disk 1st year on it but the circle D stuff was better guts inside. I cant wait to get this new motor into the car.. Robert

davanz

I have a 2016 LT1, A8, and also have been considering an aftermarket TC to sidestep all the GM engineering/fix fiasco. So I too would like to know the factory stock stall RPM rating of the A8 in a non Z06 application. Anybody know?

wrecker3

I would wait until this TSB is released !!! Doc ID: 4526930

RealmSteel

The transmission is covered under the power train warranty.
Isn't it like 5 years/60k miles?

I'll be interested in hearing how the aftermarket TC works.
I had the flush and fill done on my '16 Z51 about a thousand miles ago and it seems to work fine.
I figured if it goes past warranty and starts the shuddering crap again, I'll just change converters. I didn't really think about going aftermarket.

Internets_Ninja

If you daily drive the car you will not enjoy a higher than OEM stall converter. Also, pretty sure a higher than OEM stall will need a tune. And isn't the GM power train warranty 5 year /100K miles? You are certainly still in this window and the transmission qualifies as power train.

Joshinator99

Joshinator99

Internets_Ninja

You might want to do some research on the TCM tune when changing to a non OEM and higher stall converter in A8 and A10 cars.

sevinn

100% agreed! If even just to disable the oem slip that will absolutely destroy aftermarket converters.

Mike Mercury

are you the original purchaser?