Driveshaft parts question

[Hypr5]

Hey guys, a while ago I posted a question about my car shaking and I found the center bearing to be cracked. When i finally removed the driveshaft today, the center bearing was MUCH worse than I had thought and the rubber was brittle and was no longer in contact with the metal support.

Now my car has no guibo - its a little u-join to the tranny plate. but the back of the driveshaft has a CV joint and it easily moves to near extreme angles and im not sure if this is normal. I dont see cracks or anything, but could this contribute to the vibrations? I'd hate to reassemble this and find the same problem again.

Thanks!

[DanH]

Replacing a bad center bearing should do a lot to fix a shaking driveshaft.

What do you consider an extreme angle? The CV joint needs to move to somewhat of an angle to be able to remove the shaft. If the boot is still intact and sealed it is probably fine. The CV joint costs 5-10 times more to buy a rebuilt driveshaft than to fix the center bearing. It likely would be making noise if it is bad.

[Hypr5]

When the shaking first started happening, while reversing i heard a noise that sounded like metal slapping metal. It has since gone away and I am left with only shakes. Would that be the type of noise or would it be more of a groaning?

[Hypr5]

I know that when you disamble the driveshaft, it has to be put back together EXACTLY as it came apart or it can vibrate, but what about how it mounts up to the car? what if it doesnt go in exactly the way it came out? Can that cause shaking too?

Thanks!

[DanH]

That slapping noise you heard most likely was due to the driveshaft hitting the exhaust heatshield due to the center bearing being shot. The same thing occurred on mine before I replaced the bearing. It was a loud grinding sound.

If the shaft is out of balance that could cause shaking too, among other things, such as failing rear suspension parts. Does the shake vary with the speed of the driveshaft?


When the shaking first started happening, while reversing i heard a noise that sounded like metal slapping metal. It has since gone away and I am left with only shakes. Would that be the type of noise or would it be more of a groaning?

[Bellicose Right Winger]

Putting the driveshaft back together is just a matter of lining up the match marks you make prior to disassembly. These marks will let you put the splined connection back together in the exact same orientation. You should also match mark the front u-joint & trans output flange with a prick punch so they go together in the same orientation. Do the same thing where cv joint bolts to differential pinion flange. I'd consider replacing the trans mounts also. I'm not familiar with the M20, but on my M30 E34, the trans mounts had collapsed, from exhaust heat and age so they were about 3/8" shorter then the new ones. This doesn't seem like much but it does change the driveshaft angle, and increases the angle that the u-joint operates, which can contribute to driveline vibrations. This is particularly important on high mileage u-joints that have developed a "notch" in their range of movement. The new trans mounts and center bearing fixed a vibration I had and avoided a costly driveshaft replacement. I posted more detail on this, which should turn up via the search engine, if you're interested.

Paul Shovestul




Hey guys, a while ago I posted a question about my car shaking and I found the center bearing to be cracked. When i finally removed the driveshaft today, the center bearing was MUCH worse than I had thought and the rubber was brittle and was no longer in contact with the metal support.

Now my car has no guibo - its a little u-join to the tranny plate. but the back of the driveshaft has a CV joint and it easily moves to near extreme angles and im not sure if this is normal. I dont see cracks or anything, but could this contribute to the vibrations? I'd hate to reassemble this and find the same problem again.

Thanks!

[Hypr5]

Thanks for the reply.

Apparently I didnt notice this before, but when the u-joints are PERFECTLY centered, it feels as if there is a notch there, is this call for replacement? they swivel smoothly otherwise.

[Bellicose Right Winger]

I wouldn't worry about the notch as long as there is no play in the u-joint. I've found the notch on all (4) high mileage BMW driveshafts I've removed. But the notch could be a problem if the driveshaft angle is such that rotation of the driveshaft causes the u-joint to operate outside the narrow range of the notch. Changing the trans mounts on my car restored the proper angles and eliminated the vibration I had. 26K miles later all is vibration free.

Paul Shovestul



Thanks for the reply.

Apparently I didnt notice this before, but when the u-joints are PERFECTLY centered, it feels as if there is a notch there, is this call for replacement? they swivel smoothly otherwise.

[Hector]

driveshafts with serviceable u-joints? BMP sells them but don't know how much. I recently checked the driveshaft in my car and found some play. The driveshaft has been replaced once and was thinking about getting the one where you can service the u-joints.

Anyone have any experience with these BMP driveshafts?



I wouldn't worry about the notch as long as there is no play in the u-joint. I've found the notch on all (4) high mileage BMW driveshafts I've removed. But the notch could be a problem if the driveshaft angle is such that rotation of the driveshaft causes the u-joint to operate outside the narrow range of the notch. Changing the trans mounts on my car restored the proper angles and eliminated the vibration I had. 26K miles later all is vibration free.

Paul Shovestul

[Bellicose Right Winger]

Hector,
Fortunately I've never had to replace a driveshaft. Sorry to hear you may have worn out a second one. Is play the only symptom or do you have vibration issues also? Any chance the play you detect is really in the transmission or differential? I thought most of the rebuilders like Portland Driveline and the one in Atlanta used serviceable u-joints.

Paul Shovestul





driveshafts with serviceable u-joints? BMP sells them but don't know how much. I recently checked the driveshaft in my car and found some play. The driveshaft has been replaced once and was thinking about getting the one where you can service the u-joints.

Anyone have any experience with these BMP driveshafts?

[Hypr5]

All the bad vibrations are gone. It was just a totally shot center bearing. Yay