Diff Question Again!!!

[fushuman]

I know i asked this question and no one answered (maybe it's stupid but hey, as a famous phylosopher said, "there's no stupid q's, only stupid people" or something like that).

Anyway i have this humming noise in the rear while driving and I checked the bearings and tires. They're OK. so last thing is the diff.
Now i've read posts that says it's "lifetime" and it's sealed, but some say it's not. It's like a crazy debate or something
SO WHAT THE F#%$ SHOULD I DO? is it safe? has anybody ever changed the diff. fluid? what type should i use? Can i change it at a Castrol Center? (that's where i get my oil change)
Yes it may be stupid but i need to be sure.
Thanks

[Kevin325i]

I've changed it. Just get a good gear oil and if you have an LSD make sure you have the right fluid.

You need a special alen wrench socket however that's insanely hard to find.

[theogill]

How do you know if you have an LSD? My 328 has sport package w M suspension, but the list of options from the dealer makes no mention of an LSD.
Does have Traction tho.
Thanks.

[slyhog-22056]

I had the same problem even after changing fluids in my 633CSi. I replaced ALL the bearings and the noise is gone. It wasnt apparent the bearings were worn by visual inspection, but changed them anyway. DON'T order the bearings from BMW suppliers, the same numbers are available here, just drop the beginning letter on the bearing number.
1 bearing for mine was $69 on the net but got all ring gear, and pinion bearings as well as outer races (4 total) as well as all seal for $89 from a nationwide bearing supplier. They all crossed over to USA made bearings, (FAFNIR), If I remember right.
The biggest problem is pressing the old ones off and on, but I had access to a shop pressed and completely rebuilt the rearend and repainted it in less than 4 hours. 1 very important thing though, the shims under the outer covers for the shafts to go into are not the same thickness from side to side and are used to preload the ring gear bearings, dont mix them up, it will move the ring gear either to tight or too loose against the pinion gear. mine were .005 in difference and it does make a difference for centering the ring gear.
Dont let it intimidate you because it is different than american made diff's.

[dfw325e]

I changed mine...and i would encourage it...to keep the small metal fragments out of your rear end. I use mobil one synthetic..for diff and tran.

[97alpineM3]

When they say "lifetime"... that is a type of fluid used... meaning.. unless you have a leak or something that would cause the fluid to go away... a lifetime fluid will be able to stand a lifetime... with out change... that doesnt mean you cant change it.

If I'm not mistaken... its two 17mm internal allen head plugs... remove the top one... then the bottom... let it drain... replace the bottom one... fill till the top one has diff fluid coming out... and your done... check your owners manual for the correct type of oil.. or just search the internet untill you find.

I havnt done that in a while... this topic reminds me.. thanks...

Good Luck
Les

[bitcore]

to tell if you have an LSD:
Odds are that you don't, but I believe it was an option from the factory so it is possible.
If you have a jack, jack the ass end of the car in the air, undo the handbrake, put the transmission in neutral. Now, spin one of the tires with your hand, if the other tire goes the same direction (like if the axle was one piece of steel) or dons't spin at all, then you have an LSD. If the other wheel spins the OPPOSITE direction, you have a standard open differential.

The other way that definately works is: Do a burnout. if you have 2 skid marks = LSD. One skid mark = open diff. (don't do this, I'm kidding. It works, but it's a bad idea)