Bryan@btroutman.com

Fast81

Pretty sure you'll have to cut up the tunnel to fit that in. The 4L60E is about the biggest modern AT you fit in without cutting/welding.

lionelhutz

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.

diehrd

I run the 4l80e .. The best thing for its install are Banjo cooling line fittings. Get them off ebay . Makes for a clean install and no hammering of the tunnel

gkull

http://www.chevrolet.com/performance...e-transmission

riverracer au

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.

Engage

Why do they make the new cars with the 8 speed?

calwldlife

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.

7T1vette

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.

resdoggie

8-speeds? New ZL1 Camaro has a 10-speed. Wonder how far they can go with this? Or, maybe just design a robust CVT?

diehrd

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.

CA_WxMan

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.

lionelhutz

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.

Bryan@btroutman.com

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.

Bryan@btroutman.com

Awesomeness! I would be very happy with a 6L80E. I'm not sure if there's really much if any difference in the physical size of the 6L80 and the 8L90. But at least, based on what you are saying, I should at least be able to go with the 6 speed.

Bryan@btroutman.com

I had said in a different thread, I want to do an LT4, but the reality is, it's this the exact LT1 kit that has me thinking of doing this. I have actually seen an LT1/8L90 take off on Ebay as well. I'm leaning toward starting with something like this. The main difference in the LT4 is the supercharger. I know there are some differences in the valves as well, I'm not sure about the cam. but my C3 is 200hp. any LS based engine transmission would be a huge improvement. I'm just trying to figure out which way I want to go and how much I want to spend. Right now, I'm going to concentrate on upgrading the suspension with coil over shocks and upgrade the brakes to 13" or 14" calipers. So I'm realistically a year away from an engine swap, but if I know what I want to do, it gives my time to find the right deal and minimize the expense as much as possible.

7T1vette

Overkill, it is.... But, boyz and their toyz....

Everyone can do what they want with their car. Whether it needs it or not is a different story.

lionelhutz

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.

C3 4ME

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.

BigBill94

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.