I have a 3.92 push in non-LSD and would ideally find a 4.++ ratio but these seem very rare or non existent. Knowing that the sierra bits are generally all the same is there potential to split my 3.92 use a different pinion (for example) and create the higher ratio i need.

Essentially im now track on and never use 5th. I would like to gear it down to approx 130 to gain better acceleration.

Thanks for any help.

Iirc 3.92 is the smallest pinion (14t?) so its as high as you can go with ford bits.
SBD and Raceline make new CWPs, 4.1, 4.4, and i think even a super rare 5.1.
Last time i checked they are circa 500 quid though.

Could you change the rolling radius of the rear tyres instead?
If you use 13" rims somw carwful checking of tyre data sheets will find smaller rolling radius. As an example changing from 205/60-13 to 235/45-13 will be similar to 3.9 to 4.1 and wider footprint for more grip (needed when you have a short diff!)

You can't mix and match pinions and crownwheels, they won't match/mate

As above you can't mix and match crownwheels and pinions, they are made as matched sets.


You can get 4.1 and a 4.27 ratio from the late 2.0 scorpios (one in the 8v and the other in the 16v)
But these are all 7.5" diffs and not exactly common...


otherwise you've got the choice of aftermarket crownwheel + pinion sets, an aftermarket close ratio gearbox or smaller tyres....

[Edited on 6/4/2016 by mcerd1]

Rx8 rear diff is 4.4 in the s1 or 4.7 in the r3 I believe,big job to change though.

I originally had a 3.62 7" LSD. I am currently in the process of swapping it to a scorpio 7.5" 4.1. Not that much work involved as my diff bracket is wide enough to suit the 7.5" as well. However I had to grind some of the webbing off the casting to fit and if your prop does not have a slider the nose is about 10mm longer on the 7.5".

Your doing a 4.1 with a zx9 engine?

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Originally posted by ReMan
Your doing a 4.1 with a zx9 engine?

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