S4 Spider diff area knocking vibration at 20mph

[chris7676]

So having had my Spider for a over a month now, I have noticed the mysterious slight vibration coupled with a quiet knocking in the rear axle while the car is moving at around 20 mph. Incidentally there is a similar feeling while pulling out moderately vigorously in the 1st - as if the diff was slipping / vibrating inside. Any idea what it could be or do these sound unusual ?

[Erik Loye]

Could be the Propshaft front rubber coupling or rear universal joint or Propshaft support.
Check here Propshaft
Erik

[spiderserie4]

I would also check the exhaust/mounts are not hitting on anything at the back, before tearing into anything else more complicated.
Check Gearbox mount too, when oil soiled, it gets weak and allows the top of the gearbox (where the gearstick goes in, and the 2 breathers are etc) to knock against the side of the metal piece over the tunnel, under acceleration (as engine twists to right) This can also happen if the engine mounts are shot.

[SpiderS4]

It sounds like the propshaft universal joint.