Jim78SA

I was wondering, with people swapping to 4 speed autos into their C3s, if it was possible to swap the 6L series transmissions while still utilizing the first gen blocks? Has anyone ever done it?

cagotzmann

I also looked at this for my 78. The cost for me in Canada was very expensive. I still needed to solve the fitment issues with crossmember / driveshaft / tunnel fitment. I then decided with a T56 Magnum. Same problems to solve. Cheaper / similar in Cost. The extra was changing from auto pedals to manual. ( this has been done by many and is a simple swap since you are using factory parts.) Its a pain but nothing complicated. Now that it is complete I think I made the right choice, unless someone knows of a true 6 speed auto that would fit. TCI makes a 6 speed but it has been reviewed very poorly in reliability.

Corey_68

It will take some work for the 6L80, but it can/has been done. Word to the wise, they are huge, heavy, lots of parasitic loss.

7T1vette

What would be the advantage...other than few have done it? Expensive; need to hook up a controller and the sensors; have to modify the tunnel area;heavier. If you just need something beefy to handle your engine's power, get a well built O/D tranny.

There are some situations where the extra ranges would be of benefit...but not for most of us.

Poorhousenext

If you are going to put a 6L80e behind a not electronic controlled engine. First thing your going to need is a stand along TCM to do it. Zero Gravity Performance says they have one that will work. Will it, I don't know but price is $950.00

http://zerogravityperformance.com/pr...on-controller/

6L80E is tune sensitive, so you will need to find a tuner that can tune one, an be able to do it without ECM info.

Very low 4.02 1st gear, 2.23 2nd, 1.53 3rd, no 1-1 4th, it's 1.15 ratio, but you get 2 1st gear ratios an 2 OD gears ratios.

Next it's not a small transmission, and it's pan to ground clearance can present a problem. Tunnel will require major modification an a C3 might require Fire wall modification also. C2 didn't.

With truck pan. You can get around another 1.0" of ground clearance with a GTO 6L80E pan shown later.





Your exhaust pass thru holes in tans cross member will have to go. Probably have to make half moon ones since exhaust will to be routed under floor pan, not in tunnel.



With G8 pan.




Fitment of shifter could be worst depending on car shifter used is from. You might be able to modify an aftermarket shifter if you don't want TU/TD capability.







With your stock block, you may have problems with Flex plate, starter. Trans dip stick/fill tube for sure.

Benefit.
When parked, you get to brag about having a 6 speed auto with TU/TD or Paddle shift...LOL

You better be creative problem solver.

7T1vette

Lot of work for 'modest' benefits. You can see the amount of work from the above post. Great work, BTW!