engine and drivetrain Rotational noise directly related to shaft speed

[SteveK535]

Ok here is what I have done. New guibo and center bearing. Yes I did match shaft halves before taking them apart. Noise still there. Just put it on stand and while my son spun the rear wheels listened to the diff with a stethoscope, some faint noise but nothing unusual, listened to each of the trailing arms near the wheel bearings...nothing. Then I started the car and put it in 3rd while up in the air. Noise comes from what I think is the out put shaft of the transmission. Sounds bearing like with cyclic pulse, like a roller is bad. This noise is not gear selection or engaged related, i.e makes noise in gear, out of gear rolling, any gear...in sync with the shaft rotation. Thoughts?

[TobyB]

This noise is not gear selection or engaged related, i.e makes noise in gear, out of gear rolling, any gear...in sync with the shaft rotation. Thoughts?

Well, unless it's something easy, like the guibo is hitting the shifter,

take the driveshaft off, and see if the trans does it by itself.

I'd check the output flange nut first- they do come loose.

If it's not that, take the driveshaft off, and see if the trans does it by itself.

If it does, it's the output bearing in the trans. Which is unusual.

If it doesn't, look at the nose of the shaft carefully- it has a centering

bushing, and those can wear out. Also look at the end of the trans shaft-

the 'pin' the bushing rides on- as those can be damaged, too.

hth

t

[SteveK535]

Man, I wish I had checked the nut that last week when I had it all apart. I was convinced it was a combination of shifter interference (bare metal ring from rubbing shifter on drive shaft ) and really shot center bearing, trans mount. Did a little more research and evidently per the Rennsport site that is pretty common (or was back in the 70s and BMW failed to acknowledge it as bad design) I'll take it down again and check the nut, other wise, its likely internal any one have a good 4 speed they want to get rid of in the New England area?

[Mike Self]

had this happen with my '73 many years ago...those more experienced than I with 02 trannys told me that the ball bearing on this shaft should have been (and I think are in later trannys) a tapered roller bearing vs a ball bearing 'cause it gets some side loading--not good for a ball bearing. The ball bearing wore to the point where the race disintegrated and pieces came out with the tranny oil. Not good.

Replaced it with a tapered roller bearing...no more problems.

cheers

mike

[SteveK535]

Haven't done much research yet on this, did you do it yourself or send it out? I was thinking if that was the issue, I'd be better off getting a new tranny, but if its doable, maybe I'll tackle it over the winter.

[SteveK535]

Well, my drive shaft is back off the car again to search out the noise. Output flange is tight to the touch, however, I don't have the right size socket (thin wall) to put any torque on it. Figure the size is about 28mm, anyone know for sure? There is some slight side to side play in the shaft, which I didn't like. Started the car with the drive shaft off and the noise is still there, although less pronounced because it is unloaded. Seems to peak around 15 mph, which was 3rd gear with wheels off the ground at idle and with the running gear connected and 2nd without it. So I figure its the internal bearing(s), although I will get a socket on that nut before I get too crazy over this. I may need a reputable source for a reasonable 4 speed transmission. I'd do a 5 speed, but that means a new shaft right? I want to do it right, but not too expensively either. Any recommendations or options?

[TobyB]

It's 30mm. The generic auto stores sell a 30mm deep 'axle socket'

for pretty cheap, and if you then grind that down a bit, it works well.

I chuck 'em in the drill press and use an angle grinder. Even looks OK.

If it's still any kind of noisy with the drive shaft off, I hate to say it, but

start trans shopping. Did the nose of the driveshaft look ok?

t

[SteveK535]

The cap on the nose of the drive shaft is not uniform, it looks like it was pushed into the pin off center when it was initially installed, but the socket is OK. Unless I am wrong, I wasn't too concerned about that. I was looking on line for recyclers, ever hear of Bavarian Auo Recylers in Norther Cal? They are one of the only ones coming up on-line that I think may have them...that is of course other than Metric Mechanic, and I'm not sure I want to go that crazy, although it is tempting. I am trying locally as well, I have a good BMW mechanic/friend that I'll be talking later today. Bone yards aren't as numerous here as they used to be, so it may be a bit of a struggle to find one. Apprectiate any tips you guys migth have.