stripping down my "friends" 84'318i diff

[kaoru-tochiro]

My "friend's" differential started making a humming sound, "he" thought it was a loose exhaust so he quept driving till he heard a grinding crunchy sound, I've never experienced any diff problems before on any car so it's kinda new to me. I unbolted the diff and muscled it out, and took off the rear cover, I can see the gears and luckilly there's no damage!! no marks, but the oil has an ominous grayish paste, then i noticed the input shaft was loose, you could jiggle it up and down about 6 mm. I took off the oil seal to discover that the roller bearings are completely mangled. Now, it seems like a puzzle because I think I have to start with the pin that holds the "spider" gears, but it doesn't slide out because the ring gear is in the way. My damn repair manual (which I won't endorse) doesn't show any instructions. What's my next move?

And remember boys and girls, always check/change your oil.

[lowridder11]

1 word
SWREWD!

[kaoru-tochiro]

Hmmm, :smoka: I can't seem to take off the bolts on the ring gear, they're fused in. Even broke a socket when I tried to pry them with a breaker bar. :smoka: Let me get my monkey wrench...

[1991 318is]

i have a 91 318is and it's doing the same humm noise. Im taking it to a mechanic here tomorrow, but i think it could just be a bad u-joint? is that possible? please let me know how you do, and i will let you know about mine

[kaoru-tochiro]

91 318is, I think you might have a problem with the driveshaft center bearing, that's usually a part that wears out long before the other drive line parts. Our 84 318i has over 260,000 miles now, the center bearing was replaced around 120,000 miles 8 years ago, it also was making a humming soud.

[1991 318is]

thanks for the info...do you know what somethin like that goes for to be repaired? let me know if ya do. let me give you a good web site to get parts of you don't know already......maybe it'll help or sometime down the road.. www.bmwwholesale.net THESE GUYS ARE AWESOME, my friend bought a 1990 325i 6 cylinder motor off them for 375 bucks, they have a ton of bimmer parts. a freaking graveyard, and they are very resonable

[kaoru-tochiro]

That website is goint to be very helpfull, :smoka: thanks a lot!
About your problem, first make sure exactly what's making the noise. But to change a center bearing, they're like $60, first the heat shield must be taken out, then loosen the center bearing, it should come down without taking out the catalitic converter. Maybe a 2 hour job, fairly simple.

[1991 318is]

hey hope the web site works out for ya! :bandit:


Do i need to take off the driveshaft completely or can i just take the driveshaft off at the bearing? Let me know because that would save a ton of time not having to remove the driveshaft from the differential and the transmission....... also do you know a grease that I can get for when you put your bushing back in for when you do your control arm replacement? i did my tie rods, now im moving onto my control arms and i know there is type of grease that you point on the bushing to lubricate it then after a short amount of time it hardens and helps hold it in place... later...........

[kaoru-tochiro]

Wow, that's some magical grease :smoka: slippery at first and sticky later, sorry I've never heard of that stuff. About the center bearing, there's a nut on the shaft directly behind the bearing, loosen that and then the shaft will be allowed to get extended and sort of fold or bend down at the center without taking any u-joints off.:smoka: I hope that catalitic is not too big, I don't usually have too much good luck taking off exhaust systems, the bolts are always seized and usually break on me, hope it doesn't come to that for you. Good luck!