HTM Viper

does anyone know if a 5speed rear end will fit in an automatic rx7?

i found a used 3.9 but would rather have the 4.1 in the back

Styk33

From what I have heard there is no difference (other than the gear ratio).

FD4S

The 3.9, 4.1, and the 4.3 all fit in the auto. As long as it came from another FD, it'll fit.

The 4.3 can be found in the J-specs (later models) and provides the best solution to the auto.

I'm sure you are aware of the seriously lacking low end of the auto setup. Try a 4.3 instead of a 4.1.

CTHIS RX7

yeah they are interchangable i have used the 4.3 and the 3.9 with my 5 speed but didnt notice a hugh change in performance.

FD4S

I've heard many 5spd owners saying that there's not much of a performance difference when changing between the 3.9 and 4.3.

On the other hand, an auto transmission will surely benefit from a 4.3. The car will be rev-ing 10% higher, and would make the car somewhat more driveable in town. As an ex-auto driver, I believe the response will benefit.

7ai-7CL

I'm selling the 4.10 gear for $150obo with 9000 miles on it. tell you the truth there is a difference. i'm actually running on 4.37 right now, you will loose top end but acceleration wise its a plus. If you compare the two such as 3.90 to 4.10 there are a big difference in size. especially the pinion gear.