Half shaft rebuild question

[E46m3zcp]

Hey,

Posting here before pulling the trigger on something that will cost me near $200 in shipping.

The problem: my driveline has some slack, resulting in a loud bang/thud when shifting gears aggressively (like on track, shifting 3->4 WOT, at or near redline). A lot of jerking which, even though my subframe is reinforced, makes me fear for its integrity.

I think I pinpointed the problem to be slack in the half shafts, as can be seen in this video (please disregard whatever I'm saying, and focus your attention on the inner CV joints, which seem to be spinning, while the half shafts are not, because the e-brake is on).

https://youtube.com/shorts/aJWxB6IRCqo

SO, I'm looking to buy this from Burkhart engineering but it's costing me almost the price for the parts in shipping

https://burkhart-engineering.com/shop/antriebswellengelenk-antriebswelle-getriebeseitig-passend-fuer-m3-e36-e46-inkl-csl-bmw/

Our common distriburors have options but they're like $500 a side.

Any opinions on :
1- My problem diagnosis
2- My suggested solution

[maupineda]

You can source all those parts locally. The inner CV is a GKN part. Search the forum, a member posted the PN. I am assuming you are in the US

[E46m3zcp]

https://nam3forum.com/forums/forum/main-forum/e46-2001-2006/46356-rear-axle-rebuild-replacement/page3

ok, listed as a Porsche replacement I see

[sapote]

I think I pinpointed the problem to be slack in the half shafts, as can be seen in this video

I don't see obvious problem from the video. The amount of plays on the input is normal due to the normal ring/pinion + spinder/side-gear plays. As about the half-shaft plays, it's hard to see how much the smaller shaft rotated relative to the CV bigger dia rotation, and a very small amount of plays is due to the total plays on the 3 splined shafts for each side.

I don't see the plays in the video causing the lound clunk, but it could be from the diff internal plays for worn down LSD.

[E46m3zcp]

You're right, it's hard to check the movement of the CV joint against the smaller diameter shaft in the video. I will undo the CV-joint from the diff and double-check, but it seemed like there was the same amount of play as at the beginning of this video:

https://www.youtube.com/watch?v=mG29dLUSMFs

The end of the video shows that on a fresh part, there's no play at all.

Also, I'm suspicious of this Porsche-marketed CV joint others have used. It seems like if this were the right part, they would sell a kit with the correct boot and market it as fitting our e46 m3s, I suspect the Porsche one is not the right CV joint. People reported having difficulty installing it in the thread linked above.

[1000hp]

You're right, it's hard to check the movement of the CV joint against the smaller diameter shaft in the video. I will undo the CV-joint from the diff and double-check, but it seemed like there was the same amount of play as at the beginning of this video:

https://www.youtube.com/watch?v=mG29dLUSMFs

Interesting. The output shaft on mine has at least as much play as the CV joint in the video (checked with no axle installed). But if the joint also has as much play as the one in the video, maybe the play can compound and cause the obnoxious "M-clunk" issue.

I know sapote is gonna buck over this, but I seem to recall somone stating that their diff had been rebuilt and still clunked 🤔

It would be worth a shot for only $200, or whatever the Burkhart joint ends up costing with shipping and tariff bs.

[sapote]

“Interesting. The output shaft on mine has at least as much play as the CV joint in the video (checked with no axle installed)”

I think you meant the diff output flange which should have reasonable plays.
The haft shaft: should has no plays when holding/ rocking from cv to cv.

[1000hp]

“Interesting. The output shaft on mine has at least as much play as the CV joint in the video (checked with no axle installed)”

I think you meant the diff output flange which should have reasonable plays.
The haft shaft: should has no plays when holding/ rocking from cv to cv.

Yeah, I'm saying that if the CV joint also has play, which I haven't checked on my car, the two combined might cause a clunk. (I distinguish between the two in that first sentence).

[sapote]

(I distinguish between the two in that first sentence).

" The output shaft on mine" output shaft =/= output flange.
It's confuse to call the output flange as output shaft which is the same as the half shaft.

[1000hp]

" The output shaft on mine" output shaft =/= output flange.
It's confuse to call the output flange as output shaft which is the same as the half shaft.

Fair enough.

To clarify...
- The passenger side output flanges on these diffs often have lots of play.

- If the CV joint has as much play in the one in the video, that play combined with the play in the output flange might be responsible for the clunk on some cars.

[sapote]

Diff output flanges: V1 have more radial and rotational plays on the R; V2 diff have more radial and rotational plays on the left.
The said plays is not the root cause of the clunk, as all open-diff have the same comparable plays but they don't have the clunk issue. The clunk is caused by the LSD clutch pack sudden slip, allowing the spider gears hitting the side-gears at high speed, Bang!