My sister had a TY752vb4aa gearbox from a version 2 sti 555 fitted to her classic and I believe that the rear diff ratio was a 4.111 from the transmission chart but I need to know how to identify the rear diff that I have to know whether it's the correct ratio for this box?

Is it externally marked or do I need to open it and count the teeth or read the code stamped on the crown wheel?

Can anyone help me please?

Thanks

 

Pretty sure they are stamped from memory, if not count them as below

Ratios are :
9 - 40 = 4.444 [ 40 divided by 9 ] JDM STi
9 - 37 = 4.111 JDM WRX
10 - 39 = 3.900 JDM RA versions
11 - 39 = 3.545 Standard UK Now that is where the problem gets worse, as you
can see 3.9 and 3.545 use a 39 tooth crown wheel.

 

I thought that they were stamped too because I remember stripping one before but I couldn't find anything using a search. That's very good information though and that will definitely help thanks