Hi,

This goes to show you what I know of the 900 series.
I didn’t know a M90 was a manual shift car! I was thinking only an automatic from the sounds of the shifter operating. I guess I thought I was convincing myself that it was an automatic. (:)

So now that you have a clutch in the car, that makes a big difference!

That sounds very well could be a bad clutch assembly as it’s slipping and chattering.
Why only in reverse does seem very odd though?

Does a chirping sound happen when letting the clutch out when going forward as well?
It will be shorter in duration and more likely to happen only when the clutch is the coldest.
Did you do all that backing up first thing!
After driving the car does it become less or stop all together in reverse after all things are up to operating temperature?

Shame you don’t have someone listen outside the car as that particular sound does have the tendency to emanate from everywhere with its volume.
It should sound like it’s from underneath the car.

A Car Talk show provided a checking procedure and that’s was to put the car up against a tree or solid wall.
Then, with the car in second gear or higher and let the engine idle or slightly above and push the object.
If the engine doesn’t stall the clutch is shot!
This might also create the noise.

I would suggest using a thick blanket though and spread the load to your bumper surface with a flat piece of wood and not a tree! As they are usually round and not very big in diameter! (:)


Phil