Diff bolt question

[mrgreen387]

Do they break easy during power launch? I had problem with my old e36 m3 before but not sure if e46 would do the same thing? If so, which part number would be? I want to avoid break it because it cost a lot of money to remove the broken bolt. lol

[Tbonem3]

Old rear diff bolts (etorx) were fully threaded and too weak so they were updated to be mostly solid shank with enough threads for fastening. Just look up the parts on fcp or ecs, drivetrain.

[heinzboehmer]

There's updated parts for both front and rear bolts. Rears were updated to a design that fits more snugly in the bushing and thus reduces clunking. Front was updated because it tends to shear (I think).

Updated front: 33177840535
Updated rear: 23001222891

Saved this procedure from the old M3Forum for installing diff bolts:

Insert front bolt
Insert rear bolts
Torque front bolt to 200 Nm
Torque rear bolts to 20 Nm + 90°

Also be careful with the front bolt, I cross threaded my diff mount when doing mine.

Edit: Seems like the front bolt was not updated. 33177840535 superceded 33172282077, but the design seems to be the same.

[Tbonem3]

Hmm I don't remember that front one being updated. Do you remember when?

Rears I thought were breaking but maybe it was just that the diameter was too small. Usually making that move is for strength, but could be fit. I remember changing them out, but can't remember the front.

[heinzboehmer]

Huh just looked it up and it looks like you're right. According to RealOEM front was superceded but the design seems to be the same. For some reason I thought the front had been updated to be half threaded like the rear. Updated my previous post.

Regardless, might make sense to source a half threaded bolt if worried about snapping that bolt.

[r4dr]

There are 2x washers too (p/n 07119901766):

[Tbonem3]

You can reuse the washers, just need the newer bolts.