Question: 1978 rear end upgrade??

[cementhead1953]

I have acquired a 1994 corvette indepedent suspesion rear end. Anybody know how big a job it is to put this into my 78. Im hoping this will make a large handling and comfort difference.

 

[6880 Mike]

The C4 rear set up is very similar to that in your 78 with the exception of the use of aluminum and the fiberglass spring. Install an aftermarket fiberglass spring under your 78 and you will have effectively gained the primary benefits of the C4 rear at far less cost to you and no surgery.

 

[JohnZ]

I have acquired a 1994 corvette indepedent suspesion rear end. Anybody know how big a job it is to put this into my 78. Im hoping this will make a large handling and comfort difference.

Installing the complete C4 package is a huge tear-up, involving LOTS of fabrication, surgery, and welding; don't even THINK about it.

 

[VetteV8]

Are you sure Mike?
I thought that the C4 uses 2 trailing links, and is totally different from the C3.
I 've seem quite some mods regarding the installation of C4 set-up into the C3, which involves some cutting, grinding and a lot of welding.

Or am I totally confused now :eyerole
Cor

 

[VetteV8]

:L Someone else [JohnZ] is typing quicker than I can
Cor

 

[Peer81]

If you want to go for the perfect C3 IRS the C4 IRS will get you there only half way. If I remember correctly the "toe" problem is fixed by the two extra arms that control toe as the top end of the C4 IRS and the weird change in caster? while the wheel is in and out of the suspension has been corrected by the double "dogbone" construction (as to the original trailingarm). The problem is still that the toe arm is only a controle arm that makes that the halfshafts are still part of the contruction that controls the camber. If you want that to be fixed you're going to need some extra "strudrods" on top of the halfshafts and then make the halfshafts like a Viper has them as they can extend and retract. That makes that the halfshaft are only there as a driveline part and not a suspension part. But hey, with the C4 suspension your still much better of then the C3 has!

But if you want to adapt the C4 IRS. With a 78 the diff rear mount is different and a think 1 or 2" wider then the 80/82 batwing but as you need to fab (weld some ears to the underside of the chassis) that that is not a problem. At the front you need to fab a bracket, as you don't have the C4's C-beam to connect to the transmission the bracket need to connect the front diff to the original place. Also remember that the diff from an C4 automatic is a Dana36 and not an improvement in strength over your original iron diff. You also need to fab a bracket that holds the two "dogbones" at the front around the place where the original trailingarm is located. If you mess that up I think the suspension will be all over the place in corners so calculate where the have to be!

I think the last and biggest problem is that the C4 IRS is much wider then the C3 is. So you need new rims with lots of backspacing. Even then I hope you can make it within the C3 wheelwells.
So start by measuring the total C4 IRS width and compare that to the C3 car width. The difference between the two you need to find two rims to squeeze into that space. Good luck!

Greetings Peter

 

[cementhead1953]

rear end upgrade

That is fast replies,,thanks. As I got the rear end for free and its in excellent condition, I better measure twice regardless. Besides I have some carb work to do also.

 

[GTR1999]

Depends really on what you want to do. Personally I would not make this swap since a properly setup C2 or C3 suspension is fine for most applications. The brakes, suspension, and drivetrain are very good for daily use if in operating condition. The later C3 drove better then the earlier solid mount cars did.

As for strength I would take that 78 iron diff and build it, it will hold up better then the C4 diff if done right. I have some in up to 1000 hp cars.

I would sell the C4 setup and get the 78 back into shape if needed. Good luck.