Little backround.

Yesterday I installed a nice 3.15 lsd in my 328is. Not even 30 miles later, the rear tires lock up on the highway. As I manage to pull onto the shoulder (tires smoking and all), I realize that I can get the car into gear, but, it doesn't go anywhere.

So after a tow to my frinends house, I re-install the 2.93. Just for fun, I take the cover off the 3.15, and see that nothing looks amiss with it. No bolts are loose, no teeth are chipped. Nothing. It looks brand new. Not deterred by this, I remove the differential assembly, and try to turn the input shaft. Problem. The bearing is toast. It spins about 1/4 turn, and then locks again. Near as I can tell, the bearing failed through some unknown circumstance.

Does anyone know where I can purchase another bearing for the input shaft?

Or, am I better off looking for a 3.15 open diff, and just swapping the LSD unit into that?

:help

Well, since you have not paid me for it yet, I guess it's a free diff :confused

On a more serious note, did you swap the input flange in order for it to fit your car? Perhaps the it was under/over-torqued?

Anyway...the bearing has a part# associated with it, have you tried calling a dealer to see if it's available?

p.s. left you a VMM earlier today

Edited: reason, spoke to Bogdan

Dealer, other parts suppliers, etc. Swapping out is NOT easy. I spent a couple of hours making the correct size press dies on a lathe to get the input and output shaft bearings out of a diff I did a while back. Swapping input flanges, replacing the input shaft seal, etc, requires careful retorquing of the input shaft nut. If you're swapping flanges, you have to make sure you don't overtorque the nut, or you can burn up the bearing from too much preload. They're a pair of oppsoing taper roller bearings. That may be a cause of the input bearing failure on your diff. Sorry, it is not easy to change out for the home/DIY mechanic.

Dealer, other parts suppliers, etc. Swapping out is NOT easy. I spent a couple of hours making the correct size press dies on a lathe to get the input and output shaft bearings out of a diff I did a while back. Swapping input flanges, replacing the input shaft seal, etc, requires careful retorquing of the input shaft nut. If you're swapping flanges, you have to make sure you don't overtorque the nut, or you can burn up the bearing from too much preload. They're a pair of oppsoing taper roller bearings. That may be a cause of the input bearing failure on your diff. Sorry, it is not easy to change out for the home/DIY mechanic.

Thats a hard-learned lesson there. :(

So, how many hours of labor is that to fix. ;)

call Dan at Diffsonline...he can help you with anything you'll need...

Check the tires for flatspots too.

Dealer, other parts suppliers, etc. Swapping out is NOT easy. I spent a couple of hours making the correct size press dies on a lathe to get the input and output shaft bearings out of a diff I did a while back. Swapping input flanges, replacing the input shaft seal, etc, requires careful retorquing of the input shaft nut. If you're swapping flanges, you have to make sure you don't overtorque the nut, or you can burn up the bearing from too much preload. They're a pair of oppsoing taper roller bearings. That may be a cause of the input bearing failure on your diff. Sorry, it is not easy to change out for the home/DIY mechanic.


What he said. The last time I changed any diff bearings, I had access to a 25 ton press and a machine shop full of scrap round stock.

If you or someone you know has some experience with automotive differentials, straight bearing replacement is not difficult. The hard part is properly tightening the input flange nut because there is no a torque spec. This nut is tightened based on bearing drag torque which is related ultimately to bearing preload, 5000N if I remember correctly. Of course, you can't just stack the two pinion bearings in a press with a plate with a 1/4" drive square hole between them. This will give you drag torque for the bearings but tells you nothing about the pinion seal. Of course, drag torque due to seal friction varies widely depending on seal condition. If I had to guess without looking at any tech manuals, I would say the total pinion drag torque is usually in the couple dozen inch-ounce range. I'm sure the diff experts know new seal and worn seal drag torque numbers off the top of their heads.

dan at diffsonline.com will get you whatever you need for the diff. You should send your diff to a machine shop to get it assembled properly. You are not gonna want to have this lock up problem again after spending $ on a new bearings and spending time on trying to put it together right. I had my kaaz diff sent to a machine shop to install new hardware and gearing before it was installed.

Call up Dan @ Diff's Online and ask him his address. Then go to UPS.com and send it to him. In a little bit you will get back a working diff. Seriously though, this is not a diy for 99% of the home mechanics. There are a lot of specialty tools and knowledge needed.

-tony

Sounds like it might be easier to just find a 3.15 open diff with a 4-bolt and swap the LSD part to that. :)

That way I don't even need to mess with the input shaft and bearing replacement, or ship it halfway up the east coast.

Bogdan..listen to the others dude...there are only a few guys out there that really know diffs and diffsonline is for sure one of them! it's not a DIY...pay a few extra bucks and get the peice of mind that it's been done right and that it can take the abuse you may throw at it....diffsonline or Baviarian Performance Group...Dan and John M respectively...they work together....they'd be able to handle any questions, advice, and repair/rebuild, plus installation of your diff...or any other race/autox/street prep you may need to talk about...I've known these guys for 3 years and I'd trust them in a heartbeat!

bearings are avaiable by SFK, FAG, and maybe timken

any parts supplier that has an account with SSF can get the bearings.

Bogdan..listen to the others dude...there are only a few guys out there that really know diffs and diffsonline is for sure one of them! it's not a DIY...pay a few extra bucks and get the peice of mind that it's been done right and that it can take the abuse you may throw at it....diffsonline or Baviarian Performance Group...Dan and John M respectively...they work together....they'd be able to handle any questions, advice, and repair/rebuild, plus installation of your diff...or any other race/autox/street prep you may need to talk about...I've known these guys for 3 years and I'd trust them in a heartbeat!

Believe me, attempting to replace the bearings is something I would not attempt to do. Sometihng like that is better left to the professionals, as many others have stated.

What I would be inclined to do, is find a 3.15 open with a 4-bolt flange, and swap the LSD unit into that. :)

hey dude, sorry to hear about this.... and wish I coulda helped you tow. I guess I should buy a winch for my trailer eh? :embarrasm

Believe me, attempting to replace the bearings is something I would not attempt to do. Sometihng like that is better left to the professionals, as many others have stated.

What I would be inclined to do, is find a 3.15 open with a 4-bolt flange, and swap the LSD unit into that. :)

Then you'll have an LSD with bearings that are shimmed for a different case. Do your self a favor and pick of a copy of the TIS on ebay. Read the section about rebuilding e30 diffs. Then you might realize what you’re getting into. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>
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BTW, Autohausaz.com has really good prices on those bearings.<o:p></o:p>

Then you'll have an LSD with bearings that are shimmed for a different case. Do your self a favor and pick of a copy of the TIS on ebay. Read the section about rebuilding e30 diffs. Then you might realize what you’re getting into. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>
<o:p></o:p>
BTW, Autohausaz.com has really good prices on those bearings.<o:p></o:p>

Crap. You're right.

Shipped out it's going to be. :embarrasm