2001 C5ster

So it looks like I am going to swap my rear end gearing on my 2.73 geared automatic.
I am unsure if I want to go for a 3.15 or 3.42, but regardless of my choice, it looks like the two options are the gears or the whole pumpkin swap.
The whole pumpkin is more costly, but how does the installation cost compare? Would I be correct in assuming the pumpkin swap would be cheaper because it is an easier job? Anyone have this done?

Capt Mike

I'd go with a complete Diffy, and keep your old unit.

Go to to a site that has an on line calculator that will provide the rpm at varius speeds to help you decide on your ratio

v98roadie

You cannot put 3.15, 3.42, 3.73 or 4.10 gears in a 2.73 rear end with an A4 (don't ask me how I know this). I changed my 02 A4 rear end and went with 3.73 gears. It is as though the car and engine were built for 3.73 gears. It is a beast compared to the old 2.73 rear end. It does negatively affect fuel economy. Like Capt Mike said, go with a forum vendor and get the complete rear end, it will ultimately be less expensive and you'll have warranty. It is the single best performance mod you can do on a normally aspirated A4. Good luck.

vettpapaw

I changed mine from 2:73 to 3:15 mistake go for the 3:42!!!

Capt Mike

Some additional info.

You should check your Ist gear ratio and OD ratio for the trans in your C5. These numbers make all the difference including your tires circumference.

My C5 Vert IPC has a 3:42 Diffy with a manual 6 speed with different than normal stock trans ratios,,, 2.66 first gear, 1 to 1 4th and, 0.5 for 6th. I really like this combo, good power and lots of overlap so not so much shifting

I haven't got around to checking the 2004 FRC ZO6 Le Mans ratios. It seems to be a little closer different 1st, 2nd and 3rd. But with a large HP increase, hard to tell - it's a power shop I'm pretty sure the ditty is also a 3:42

The C4 Vert is a ZZ4 350 Hot Cam Fast Burn with a Doug Nash 4+1, and a 3:73 diffy ratio.. The first gear is a 2.88, forth 1 to 1 and OD is around 0.62. This Car jumps out of the hole. But but without the 2,3 & 4th OD, the 3:73 diffy gears would be too low for me if it was a DD (daily driver) She's FAST & jumps and has great response, but I pay the price...

My '56 210 Coupe is a WS6,, LS1 (with goodies) T56 and a 3:50 9 inch diffy. I seems to recall Ist gear is also a 2.66, 4th 1 to 1, 5th 0.75 OD and 6th 0.50 OD

All of the tires are very close to the same circumference.

The C5 vert with the 3:42 diffy is the most comfortable ride and all around great driver. A smooth gear combo and relaxing.

The C4 with the Hot ZZ4 and 3:73 diffy is a Wild Child. has the Z51 suspension package + and is like driving a Go Cart, a blast to drive - But not for a dd,, she wears me out.

My '56 210 Coupe is the very best diffy ratio with 3:50 9 inch locker diffy. A very good Ist gear and there is a wide MPH range in 2nd gear up. 6th is mostly 50 MPH plus. She is a fast car, lightened here and there.

So there you go. Be sure to check your Ist gear and top gear ratios and run the numbers.

Call Mark and Vette Nuts, he's the man to talk to for a good used diffy and a ratio selection. He's very knowledgeable and drives a Vette. I'm very happy with all my dealings with him !!

Good Luck... Michael. PM if you need any more info...

v98roadie

If you change out the 2.73 for a 3.42 or 3.73 you'll need to have someone do a little programming to change shift the shift points (not sure on a 3.15 since that was a factory offering). There are a lot of threads on changing out the diff in A4's. Do a search and you'll find a ton of info.

SaberD

You can, but you have to put in a ring gear spacer.

C5 Pete

If you buy any C5 diff, no matter what R&P are in it, it will bolt right into your car with no modifications necessary.

You will, however, need to have the tune adjusted for the gear swap so it will shift properly.

You might want to consider a new converter too... While you're in there an all...

tiojames

It's fairly easy to find a good used 3.42 as the Z06 guys take them out and install 4.11s. Should be able to pick one up for $500.
I went from 3.15s to 3.42s on the vert.

Bill Curlee

Some things to consider................. When you remove the differential,, there are some MAINTENANCE ITEMS that you may want to consider:

1. Change the Transmission fluid and filter and make sure that its PROPERLY FILLED.

2. Replace the Torque Tube Propeller Shaft Rubber Couplers (high mileage C5 almost always have worn /aged/cracked bushings.

3. If you purchase a used differential, An AUTOMATIC differential will have an aluminum BULKHEAD installed between the differential and trans that the manual differential doesn't have. You have to reuse your bulkhead if you purchased a manual diff.

There are some improvements that you can do to make the C5 differential BETTER!

Take a look at these post. At a MINIMUM, make SURE that the limited slip clutches and beleview springs are good in the used differential. The OEM springs are well known to CRACK.







Improvement Post:

- C5, ragtopws6 , Upgrading your C5 rear with C6 Z06 guts, : http://forums.corvetteforum.com/c5-g...-z06-guts.html
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- C5, Its_Go_Time, Output Shaft Install - Left and Right: http://forums.corvetteforum.com/c5-t...post1573407966

- C5 Differential Seal replacement: http://forums.corvetteforum.com/c5-g...on-photos.html