What would happen if you put a WRX gearbox onto a UK spec rear diff?

Scott

 

Somethiong would go POP, within a fairly short time, if you're gonna do that, you'll need the rear diff aswell, that way it'll be fine!

 

do you want a rear diff?

 

I have just had a wrx box fitted and suspect the diff wasn't changed and so far it hasn't gone pop!
I think i had better talk to the garage before i drive my car anymore!

 

Depends, Having said what I said, if it were a bugeye wrx, then it'd probably be ok, but if earlier then it ai.n't

 

MY 94. I have driven about 50 miles with it. Will I have buggered it up? What happens if it does go pop do the back wheels just lock up or a grinding noise? so far no noise.

 

I don't think it'll bu66er the rear diff, I think it'll muck up the centre one in the new box, the rear diff should be an lsd, where-as the centre is probably a viscous coupling which will allow slip, but it won't appreciate slipping all the time, it's designed to allow slip when it needs to, not continuously!

 

Thanks Ron. I am armed with info now when i talk to garage

 

hang on,

when you say wrx, do you mean classic shape jap car, or new shape uk car gearbox on to a classic shape uk car.

If the second, you may be fine, if the first you will be causing your centre diff to take up the speed differential, since the front wheels will be turning slower than the rear wheels.

It is a viscous centre diff in your car meaning the fluid in it within 50 miles or so would be boiling! you may be fine, but I wouldnt drive it much further without either changing the rear diff to a 4.44 final drive, or getting the correct gearbox.

BTW if you change your rear diff to a4.44 final drive your speedo will be wrong as it takes the pulse from the gearbox without taking into account final drive ratio.

Your speedo itself knows what the pulses translate to in terms of speed as it will have been calibrated for a 3.9 final drive.

In short you will need a jap spec instrument cluster or to have your pulses multiplied by 4.44/3.9 electronically by calling a company such as protec in bristol.