i have a bad vibration when excellerating hard mostly in first gear getting less the higher the gear . i've changed the diff ,the prop looks new and cant see anything wrong under the car,bushes ,ect.
it had a new gearbox just before i bought it and i was wondering if they fitted a box with wrong center diff ratio would that cause the vibration.
if it had the wrong ratio center diff would'nt it vibrate all the time because its smooth when not booting it.
the rear diff is 4.4 does any one know what ratio the center should be, the cars a sti/4 1998.
cheers

 

I have EXACTLY the same problem in my MY99 GC8 that just got a 4.444, and i just changed the prop.

Did you get a result?

geoff

 

I think there is a manual way of checking the diff ratio by marking both the prop shaft & cv joint. Do one full turn of the prop shaft & count how many times the cv joint rotates.
i.e if you have marked the cv joint at 12 o'clock you should get four full rotations & a bit = 4.1 any thing over 3.00 o'clock after 4 rotations=4.4 etc for one full rotation of the prop shaft.
I was lucky when I sourced my g/box as I didnt know which ratio's my car was running, the chap who supplied me the new box also checked the ratios using a similar process as above