Clunk in Rear, Differential Or Differential Bushing?

[katism04]

I'm having a bit of trouble with my 2005 3.0 Z4. At low speeds when I'm accelerating or shifting there is a distinct clunk coming from the back. I took it to one shop today and they said that the differential needed to be replaced. This car has 55k miles, seems a bit extreme for a car of this mileage. They showed me that the differential was leaking a bit (the area was a bit moist) and while shifting, there was a bit of a hop/skip in the mechanism.

I called a second shop to get another opinion - they won't be able to see my car for a couple days, but they said that they've almost never replaced a differential at that mileage. They are thinking it might be more related to the bushing.

Anyone have a similar problem that can help me out? Would like to avoid having to buy an entirely new differential (was quoted $1646 for the part itself, $300 for labor).

Thanks!

 

[GP20]

Maybe change the differential oil and make sure everything's sealed properly before spending the money for a brand new differential? Those things aren't cheap.

 

[rabman5]

I had a rear bushing fail on my 04 Z4 3.0. I didn't hear a clunk, but there was an awfuk grinding sound at low speeds. That happened at about 20k miles.

 

[JimExpl]

Min does exaclty the same. From previous experience in rwd cars I expect that it's either the diff, or the UJ bearings have worn on the propshaft. I'll try and get it looked at next week. The prop bearings aren't a serviceable item from BMW, but I am sure that a specialist will be able to repair them.
If it's not this then I'll renew the diff oil and use an additive to queten things down.

 

[katism04]

So, I got the second opinion on my car - apparently there is nothing wrong with the bushing or the differential, and instead, the clunk I hear is from the transmission. It's a normal gear sound that just happens to be louder than normal in my car. I'm secretly relieved I won't need to pay $2000 for a new differential, but it's a little unnerving to hear two completely different diagnoses...

Well, I guess for now I'll just have to wait and see, and hope the car doesn't suddenly explode!

Thanks everyone =D