Drive Shaft Carrier Bearing Replacement

[kfine]

I have a 2003 S8 with 175k miles. I think my drive shaft carrier bearing might be failing. I've had a slight vibration/thumping on initial acceleration for probably the last 6k miles and now I'm hearing a rotational screeching noise from the drive line. I haven't put the car on the lift yet but the vibration symptoms are exactly the same as on my BMW E38 750il when its carrier bearing was failing. I'm having some difficulty finding the carrier bearing. I found some other thread about replacement of the entire drive shaft. Does anyone have any info on this procedure?

[Stromaluski]

Greenville, SC? I'm in Taylors, right by Lake Robinson.

[kfine]

Hey Strom,

Pretty sure we follow one another on instagram im kfine12183 on there. I'm in Travelers Rest. Ever had to replace the carrier bearing on your S8?

[Stromaluski]

PM'd.

[kfine]

Following up for anyone reading this in the future:

So, not only was my carrier bearing bad but either the Ujoints are squeeking or the CV type joint at the rear of the shaft is. I didn't pull the shaft yet so couldn't pinpoint it. I bought a carrier bearing assembly and was planning on swapping it out today, but after looking at the shaft I'm not seeing a way to separate it. There is not a bolt holding it together but rather some odd fastener with a 32 point star about 21 or so mm in diameter. I was expecting to find a 17mm bolt like on some video I watched about an A8. There is a hole in the center of this fastener which might accept an allen key. but with the other parts of my driveshaft I'm thinking I'll see if I can source a replacement.

[kfine]

Got a new shaft out of a place in TX.


Install it and there is a drive line vibration. There are weights on the shaft so I assume* its properly balanced.
Took it out, moved the carrier bearing around centering it as best I could. Measuring with a mechanics scale.
Install it and the drive line vibration is worse.



Now I've ordered the dumb expensive snap-on 3139 dirveshaft alignment tool. Hopefully I just need to get the right shim size in there while the driveshaft is straight.

[Stromaluski]

Good to hear there is progress!

[kfine]

Got the special tool and the special spacers.



moved the carrier around per what appears to be an Audi service manual procedure I found somewhere online. I ended up adding 5mm shims on top of what was already between my carrier mount and the body. The vibration is mostly gone. I'd say about 98% gone. I'm going to drive it some and maybe mess with it more in the future the next time the car is on the lift.

I'm a pro at removing the exhaust at this point and have all the bolt sizes and torque specs for the hardware involved memorized. I've done this now 4 times.

[Stromaluski]

Got the special tool and the special spacers.



moved the carrier around per what appears to be an Audi service manual procedure I found somewhere online. I ended up adding 5mm shims on top of what was already between my carrier mount and the body. The vibration is mostly gone. I'd say about 98% gone. I'm going to drive it some and maybe mess with it more in the future the next time the car is on the lift.

I'm a pro at removing the exhaust at this point and have all the bolt sizes and torque specs for the hardware involved memorized. I've done this now 4 times.

Nice! It would make sense that shims would need to be added since engine/transmission/diff mounts will sag over time, but the center support is solid mounted.

I may have to see about borrowing that tool from you at some point if I can ever get around to doing the manual swap in mine.

[Gosser]

Nice, never seen what the actual tool looks like. My brother made the same tool with two bars of square tubing and angle that he welded up, then you just zip tie it to the drive shaft. It worked out on his B5 S4. And this is me using it on my B6 CVT to quattro swap to align where I needed to weld the center bearing support brackets to the body:

[kfine]

I think the alignment tool might be just a waste of time and money. I've replaced driveshafts and carrier bearings on a few BMW's and Mercedes and I've never used or even heard of one of these alignment shafts. I've not had any vibration issues on the other cars where I've performed this service. This S8 shaft is a real pain. I went back and got the old shaft from my buddy's house and was going to try to see if I could find a way to separate it.

This is how the shaft is assembled. I noticed this morning that there is a snap ring on there


Snap ring removed but not sure that the shaft is just going to simply separate. I stuffed a large pry bar in there which did absolutely nothing. Not sure how hard I want to pry against the U-Joint.


Out of time for now.

[kfine]

More of this nonsense.....

The old driveshaft is junk. the U-joint is so bad that I can barely move it by hand. I ended up separating the shaft, and replacing the failed carrier bearing anyway, but then when I put the shaft back in there was an awful drone. Also, since I wasn't planning on trying to ever reuse that old shaft, I didn't cap the CV joint ends and some of the ball bearings fell out, therefore I have no way to tell if when I reassembled them the bearings were put back into their original place in the CV.

So back to the new shaft... I took the new shaft to a local driveline shop who's built other custom driveshafts for me in the past. Had them check the balance on the new shaft and I guess it checked out fine. I put the new shaft back in with some different size shims and that seems to have eliminated most of the vibrations. I still feel some at about 45mph and 65mph, but don't feel anything under acceleration. I've driven the car about 200 or so miles. It's still not right. I might just keep trying different size shims 1mm at a time until its good. What a pain.

[Stromaluski]

So back to the new shaft... I took the new shaft to a local driveline shop who's built other custom driveshafts for me in the past.

What shop is that?

[kfine]

What shop is that?

I had Carolina Driveline check it out so I'm sure it's correct.

I took the exhaust off and re-shimmed the carrier again this morning. Went from 3.95mm shims to 4.5mm shims and the vibration is the best it's been yet. I now have a higher frequency vibration at speeds 80+, but the vibration at 45 and 65 is mostly gone. Also noticed that now my AC doesn't blow cold and I have a new oil leak. I haven't driven this car outside of test drives since June. It just sits in my driveway and breaks down.

[kfine]

And the oil leak is gear oil from the driver front axle seal. Seems all that sitting around and not driving has worn it out . It went from absolutely dry to a dripping leak during the time my wife drove it 8 miles yesterday... I feel like moving this thread to the classified section.

[john_gonzo]

2003 A4 owner here. The A4 has a dot on the rear differential input flange and a dot on the driveshaft. The flange (or driveshaft) is supposed to be rotated until the dots are aligned prior to bolting the driveshaft to the flange. Disregarding this can introduce vibration.

Perhaps your beast is the same?