Hi, I was wondering how would a 3.9 differential upgrade suit an otherwisw stock 2000 auto C5. Is it worth it?

Regards

 

Well, it will provide a great deal more torque multiplication than even the factory "performance" axle ratio. The car will feel like it picked up a lot of "GO1" from a standing start, and be much much preppier in slow streets around town.

Somewhere in the technical or general discussion topic areas, a long time ago, I added a very long discourse about axle ratios and the pros and cons. One point to think about is that there will be speeds where the stock car has more power: the 3.9 car has had to shift into second and the stock car is still in first, etc. Still, overall it will make the car faster feeling and a bit faster at the track.

It will also rev much much higher when cruising at any speed and get poorer gas mileage.
A 3.90 ratio is pretty extreme. If you go with a 3.42 you still have 10% more torque and about more than a quarter more than the standard axle ratio multiplication that the factory performance ratio.

 

3.42s are very common swaps into A4 tranny C5 Corvettes. Lee is right in that a 3.90 is extreme for an A4. I do consider a 3.90 as a good replacement for a coupe or vert's 3.42.

 

I really appreciate the help available on this forum, especially Mr. Lee Willis.

i am in the process of ordering the 3.90 set up, however living in pakistan makes it difficult for me to fulfill the conditions of a core exchange so i will just order the ring and pinion set and have the gear ratios changed on my existing diff instead of buying the entire pumpkin. Any ideas if it would work.