prop or box knock????

[luxconvertible]

not to sure wot to do? do i need a new prop? or is there something else i need to replace? wot it is theres a funny nock when u come off of the gas sounds like the exhaust but i no its not please could some1 assist its been like this 4 sometime now though!!
thanks Ben

[Simon13]

could be your centre prop shaft bearing when they go they can bang against the heat shield, but of a pain in the arse job to do! do you only hear the knocking when the car is moving?

[mrLEE30]

Could also be the axle bushes which really are a pain in the arse to replace, this was the case on mine and some special tool required to do job properly which only at BM dealers, we got round it eventually, the symtoms were when crusing especially at around 60 in 5th then off the gas and a thump is heard from the back. Prop bearing noise you would hear and feel more toward the front of the car and if so bad would vibrate too, changing that is fairly easy, take off exhaust, remove heat shield, remove prop, disconnect prop (marking the two pieces so that when reconnected it doesnt vibrate) then change the bearing. good luck mr lee

[kevin316i]

Sounds similar to a sound that I have in my 316i. I thought it might have been the diff, but it was still there after the diff was replaced. Its more of a rattle sound rather than a knock. Will be bringing in car soon for new brakes on front so I'll see if the mechanic can shed any light on the issue and I'll let you know.

[mrLEE30]

Kevin,
if its a rattle from the back check the top of the shock absorber mounts, pull the plastic carpet thingy out of the boot climb inside and have a mate bounce the car, you may see the shocks moving up and down where the rubber has perished, replacement is easy, but for a quick fix undo the bolt and stick a big washer in there. mr lee

[Simon13]

If your getting banging like that from the axle carrier bushes they must absolutly mullered. They often charge more to change them if they are really shagged. And really is not a job unless you are a very good home mechanic, plus you need the tool!