varkwso

I just swapped the diff in my 99 FRC. The one rebuilt by Lamar Walden was out of a 2003 ZO6 (T1 Road Atlanta casualty). I hear there are differences in a C5Z diff from the rest. Looking at them side by side they appeared to be identical castings with the only difference being the tag on the C5Z diff said 3.42SP instead of 3.42 on my FRC diff. So what are the differences, other then the shot peened gears?

New gears, heavy duty clutches and bearings - amazing how much quieter it is in the car!

travisnd

2001+ differentials got a 3-rib case and then there's the shot peened gears, but you already knew that part. Other than that no differences AFAIK.

varkwso

Where is the "3 rib". Internal?

travisnd

External... the structural ribs along the top of the diff case.

Here's the stock 3-rib 3.42 out my old '03 convertible. I sold the car with a 3.90 rear in it. I don't have any pics of a single-rib older-style case.

varkwso

The one out of my 99FRC looks like that - course no guarantee a previous owner (both were track junkies) did not replace it before I got it.

travisnd

Then it was replaced

I think this is the single rib case. Front center part has one vs. three.

sperkins

Here's the one in my '99 FRC. It's a single rib.
At first I thought it must have been swapped with a C6 unit because it has 2006 written on it with a sharpie. I never put 2 and 2 together that meant it was serviced in 2006.

travisnd

It really only matters if you're drag racing.

varkwso

The one out of my 99 FRC must have been replaced since it is definitely the 3 rib per these photos and was not out of a ZO6.

ptindall

Perhaps you answered your own question?

Jaymz

I have broken a couple of them on the road course.

varkwso

The casting was my real question since my two were identical and were not supposed to be.

varkwso

What have you NOT broken on a road course ( I have a replacement spindle for you BTW)?

travisnd