8L90E Transmission
Thread Starter
Cruising
Joined: Mar 2018
Posts: 10
Likes: 0
From: Flower Mound TX
8L90E Transmission
will an 8L90 fit the tunnel of an 82 model? Has anyone put a 6 or 8 speed automatic into an 82 model? I’m interested in doing a 6.2L LT1 conversion. I’d like to also have more gears. Right now I have nothing eminent going on. I’m trying to determine how far I can go without destroying my car. I want my 82 collectors edition to retain the mostly stock look.
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
I believe Zip has a 6L80e in a C3 and they said it fit without cutting. If not Zip, then it's another one of the forum vendors.
There are a few members with 4L80e transmissions and they didn't cut. The TH400 was a factory option so the tunnel is not as small as some people try to claim it is.
There are a few members with 4L80e transmissions and they didn't cut. The TH400 was a factory option so the tunnel is not as small as some people try to claim it is.
Last edited by lionelhutz; Mar 16, 2018 at 09:19 AM.
Team Owner
Joined: Apr 1999
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Melting Slicks
Joined: Oct 2010
Posts: 2,276
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From: "ɹǝpunuʍop", Adelaide, South Australia
Why would anyone need/want 8 gears in a C3?
I can understand a auto 4 speed with OD, or a 5 speed manual for cruising and fuel econ,
But 8 seems like massive overkill.
I can understand a auto 4 speed with OD, or a 5 speed manual for cruising and fuel econ,
But 8 seems like massive overkill.
Racer
Joined: Oct 2001
Posts: 474
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From: Portage La Prairie Manitoba
Team Owner
Joined: Jan 2007
Posts: 53,648
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From: Southern Cal Ca
St. Jude Donor '22
if, if you can get a controller for shifting and
enough pump pressure, would be real sweet
setup.
try and get the ability to manual shift at times.
size wise, i don't know if it will fit.
enough pump pressure, would be real sweet
setup.
try and get the ability to manual shift at times.
size wise, i don't know if it will fit.
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Team Owner
Joined: Jan 2006
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From: Crossville TN
They need 8 speeds on some modern cars because the engines have a more narrow power band and the extra gears allow the engine to stay at higher rpm throughout. C3 engines have a wide power band and have no need for 8 speeds. You could have 'bragging rights' that you stuck one in your car. But, that's about as big a benefit you will get for doing it.
Had a 1976 L-82, 4-sp
Joined: Mar 2011
Posts: 5,338
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From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
8-speeds? New ZL1 Camaro has a 10-speed. Wonder how far they can go with this? Or, maybe just design a robust CVT?
Safety Car
Joined: Jan 2009
Posts: 4,000
Likes: 299
From: New York
They need 8 speeds on some modern cars because the engines have a more narrow power band and the extra gears allow the engine to stay at higher rpm throughout. C3 engines have a wide power band and have no need for 8 speeds. You could have 'bragging rights' that you stuck one in your car. But, that's about as big a benefit you will get for doing it.
So I have to disagree. 8 Speeds on a SBC or a LS are equal.
Take a stock L48 TH350 floor it . It will 1-2 shift at 40 or 45 mph.
The motor will be spinning at 5600 or so and once it up shifts By By rpm's. You drop to 3k or so and have to re-build your power back up to 5600.
In the 8 speed your 1-2 may occur earlier but your motor will remain at 5600 as long as you hold your foot down. That is an efficient use and application of "Power"
The same applies to cruse power. When you pull away from a light You will maintain your rpm accelerating until you reach your desired speed. The motor will drop VERY few RPM between gears making it more efficient.
Its a win win , not a bragging right at all.
Racer
Joined: Jun 2012
Posts: 269
Likes: 52
From: Springfield, TN
I'm not sure how much larger the 8L90E is, but I can tell you that a 6L80E does fit. There's not much clearance, especially around the bellhousing and at the rear part of the case, but it will fit.
I have an LS2 and a 6L80E that I mocked up in a '76 parts car, just so that I could see if it would fit or not. The plan is to put those into my '71, but I've been having so much fun doing autocross with it that I don't really want to tear into it right now. Maybe I'll put it in once I get the '75 vert back on the road, that way I won't have both cars apart at the same time.
I have an LS2 and a 6L80E that I mocked up in a '76 parts car, just so that I could see if it would fit or not. The plan is to put those into my '71, but I've been having so much fun doing autocross with it that I don't really want to tear into it right now. Maybe I'll put it in once I get the '75 vert back on the road, that way I won't have both cars apart at the same time.
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
The new LT1 has over 400 ft-lbs of torque from about 23000 to 6000 rpm. More torque and a wider powerband than any stock C3 had and even better than many modified C3's. Any claims or implications that this engine needs more gears in the transmission because it lacks a wide powerband like a C3 engine has are simply false.
Thread Starter
Cruising
Joined: Mar 2018
Posts: 10
Likes: 0
From: Flower Mound TX
It probably is overkill. I'm planning an LS conversion. I'm trying to figure out what my options are and how far I can take it without ruining my car. I don't want to cut up the tunnel. I would like to put an LT4 in it. I'd like to put the LT4/8L90E combo similar to a c7 z06. It may not happen, but I'm trying to figure out exactly how far I can take it.
Thread Starter
Cruising
Joined: Mar 2018
Posts: 10
Likes: 0
From: Flower Mound TX
I'm not sure how much larger the 8L90E is, but I can tell you that a 6L80E does fit. There's not much clearance, especially around the bellhousing and at the rear part of the case, but it will fit.
I have an LS2 and a 6L80E that I mocked up in a '76 parts car, just so that I could see if it would fit or not. The plan is to put those into my '71, but I've been having so much fun doing autocross with it that I don't really want to tear into it right now. Maybe I'll put it in once I get the '75 vert back on the road, that way I won't have both cars apart at the same time.
I have an LS2 and a 6L80E that I mocked up in a '76 parts car, just so that I could see if it would fit or not. The plan is to put those into my '71, but I've been having so much fun doing autocross with it that I don't really want to tear into it right now. Maybe I'll put it in once I get the '75 vert back on the road, that way I won't have both cars apart at the same time.
Thread Starter
Cruising
Joined: Mar 2018
Posts: 10
Likes: 0
From: Flower Mound TX
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
Why are you posting here if your only intent is to call the OP names and make fun of his plans for his car?
Have you actually got a technical reason against a 6 or 8 speed transmission? They give tighter gear spreads which keeps the rpm in a tighter range as it shifts which makes a big difference in how it drives. The 6L80e has proven to be a fairly tough transmission, and the 8L90E seems to be too.
If you go on about needs, then why should anyone do any upgrade to a C3? There isn't one upgrade that is needed. A 4-speed automatic shouldn't even be acceptable to you if you're using need as the requirement for doing it.
Last edited by lionelhutz; Mar 18, 2018 at 02:40 AM.
Le Mans Master
Joined: Oct 2005
Posts: 6,247
Likes: 471
From: Glen Allen, VA
I would call Zip Corvette and talk to them about their car. Yes, they're the ones who have done a 6spd auto in their test bed 76. I've seen it as I go there all the time. I haven't asked a whole lot of questions about it because mine's a 4 spd manual, and I'm not really interested in an auto. I'm sure they'd be happy to give you all the details of their car.
Instructor
Joined: Mar 2017
Posts: 161
Likes: 53
From: Spring TX
There's a little bit of detail in the Zip Corvette catalog. The conversion (including the transmission) is spendy for the 6L80E given it's capacities (assuming it's stock, doesn't say). The catalog shows $6K including the transmission. There's a shop in Houston that can upgrade the 6L80 to take big power, it's a bunch of dough.
C3_4ME's advice of calling Zip looks to be spot on.
C3_4ME's advice of calling Zip looks to be spot on.