3.9 to 3.54 output shaft
 

Hey all,
I was wondering, if I have an STI 6 speed gearbox with a final drive of 3.9 and I want the rear diff to receive a final drive of 3.54, what ratio would I need to change the factory output shaft to?

The current is 1:1 ratio output shaft (31 teeth). What output shaft would I need to accomplish this?


Here is a picture of the output shaft and transfer gear:
https://cimg4.ibsrv.net/gimg/www.sco...a786e19b22.jpg


I found some output shaft part numbers on the internet but can find any information on how many teeth they have.

33128AA160, 33128AA180


Any help would be much appreciated!

Thanks

It would need to run a 1:1.1 ratio.
The later GDB cars ran a drop set ratio of 1:1.1 with a 3.54 rear diff. Off to top of my head it started from revision F.
So basically, MY06-MY07 cars should run the 3.54 setup from factory, so thats the model year you should be looking at for parts in terms of converting your gearbox.
Best bet would be to speak to @stockcar, it's very likely he will have done this at some point and be able to help further.

Thank you very much for the info! Appreciate it!

Found this part number 33128AA320. I wonder if this could be the right one.