I have impreza turbo classic saloon. I have just changed my springs (lowered by 25mm) and have changed my wheels to 18 inch. It may be total co-incident but now when coasting under load down hill in gear or on the flat I am getting a whining noise coming from the rear offside wheel. It only makes the noise at certain speeds (nosiest at 40mph in 3rd/4th gear) and when you dip the clutch and disengage the transmission the noise goes away completely. Under acceleration the noise doesn't appear to be there either.


Reverse has got very noisy also.


Is this possibly due to the modifications I have made or could it be the signs of worn diff?

 

Id say its transmission related poss thrust bearing, as when u say clutch depressed the sound is stopping, your mods possibly have caused something a chain reaction on a part.... not sure. but 18s will also increase road noise depending on width of wheel ( foot print ) on road. try a lazer alignment this might help. im having rear wheel bearing done tomorrow in hope it will cure my rear noise , which is there in gear or out of gear, and changes pitch as speed changes.but again could be cv joint could be calliper dragging. good luck.