My STI 4 rear diff has started making some unpleasant noises. Not the usual whine of say a high milage one - mine's only done 30K - but a 'clonk' like somethings loose. Under normal driving: pulling away, braking, turning etc its fine, but, when you rev to say only 2000rpm and depress the clutch, let the revs drop and then let the clutch out quickly there is a 'clonk' or two - sounds like transmission shunt. I've had the car in the air and the noise seems to be coming from the rear diff. - a friend rotated one of the rear wheels back and forth fast by hand and the noise comes from the front of the diff. It sounds like something loose (or broken) almost like a small hammer tapping on solid metal! i.e. not worn, just slack. The car drives fine. Naturally I'm a little concerned and the car is booked into my local main dealer - what is at the front of the diff - where it joins the propshaft? Is there a bearing that could be loose/damaged?

 

Yes...There should be a bearing or two holding the pinion in alignment to the crownwheel......

 

It is quite possable that the if it is not a bearing problem,then either the crownwheel bolts are starting to come loose or the pre load on the diff plates needs re setting

Rob

 

This sounds like my diff

"pre load on the rear diff needs resetting" - is this expensive, and is it a specialist job?