Knocking while in gear

[rbartongrimley]

For a while now I have had this problem with my 87 ETA. What it is, is a loud knocking noise almost like when you run a stick along a fence. It only happens when the car is in gear and there is torque on the rear end. So I can be coasting along at 40mph and it will be making the knocking noise and then i will engage the clutch taking off torque from the rear end and the noise will go away. It also seems to be coming from the left rear wheel well.

The weirder part about this is if i stop driving the car for about a week then start driving it again, the noise will not come back for a good 150 miles of driving.

I checked my wheel bearing, and it does have a little bit of play but if that was the problem then it would be making the noise whether or not there was torque on the rear end. I am leaning towards it being in either the left axle or in the differential, but how should I go about checking these items? I have a parts car, so I am contemplating just swapping in another differential and axle but I still don't know if that will fix the problem.

Any suggestions?

[rbartongrimley]

BUMP.

Any ideas?

[Knockenwelle]

When you push the clutch pedal, you DISengage the clutch.

Check the driveshaft CSB and guibo. If OK, it's probably a clutch or trans mechanical problem. How's the trans fluid look? Does it make the noise in all gears, including neutral and reverse?

[rbartongrimley]

When you push the clutch pedal, you DISengage the clutch.

Check the driveshaft CSB and guibo. If OK, it's probably a clutch or trans mechanical problem. How's the trans fluid look? Does it make the noise in all gears, including neutral and reverse?

Oh yea sorry about that.

I checked the driveshaft already and replace the quibo. I changed the trans fluid very recently because I replace the rear main seal, shift shaft seal etc. I have not heard the noise in neutral, and i have not got going fast enough in reverse to see if it makes the noise.

[JuanPabloBongto]

BUMP... I bought Rory's car, and this problem has surfaced again.

I'm getting a click from what sounds like the left rear, frequency increasing with road speed.
The noise is intermittent... most noticeable between 10-30mph, and sometimes will come and go during one drive.

1987 325(eta) 5speed

Sounds JUST like a front-drive car with a bad CV joint. You know, like someone dropping marbles into a 10-gallon paint bucket.

The CV boot is not open.
I have eliminated U-joint as a possibility.

CV?
bearing?
diff?
How can I tell which is the problem??

[JuanPabloBongto]

--------------------------------------------------------------------------------

Well, just had it driven and looked over by a friend of an aquaintance who happens to be a local BMW tech. QUite a coincidence since I'm 1500 miles from home.

In his opinion it's the differential (open 3.25 I believe).
noise always happens in gear, grows under hard decel/accel, quiets under throttle lift-off
Noise goes away RIGHT when you stab the clutch pedal,
noise does not waver or cease when you swerve l/r, clicks no matter the lateral load

I'm going to drive it home... I don't have my tools so I couldn't swap the axle here unless I paid a shop $2-300 to do it.

[Rob]

is it RPM dependant (ie only happens at certain RPMs) or is on only when you're on the throttle? Looks like its the second from your description

[JuanPabloBongto]

I drove it back from out west, and that car is fine... clicking has even gone away for the most part (still occurs at low speed)

I'll be putting a spare LSD on the car so I'll swap in new axle shafts as well.

[Philo]

I'm bumping this thread for an answer. I've got the same thing going on. I've checked over everything on the rear. I can only assume it has something to do with the input flange. What's the proper way to asses the U-joint on the end of the driveshaft?

[jlevie]

The symptoms describe by the OP suggest a failed center support bearing. In almost all cases a failure of the CSB will be caused by binding u-joints in the drive shaft. Meaning that the only real fix is to replace both at the same time.