Doing a diff rebuild.

[sapote]

No you're fine. Their shim is conical, so it'll compress when installed and fill the gap as needed.

The other option is to measure the play and get a flat shim that's correctly sized. Accomplishes the same thing in the end.

Using the conical shim is for the convenience of one size fits all (gap), but it has some trade off: it has small contact areas (just a circle on each side instead of the whole shim area) and so it will wear out faster; it creates a tight mesh on the side-gears and the spiders, and could cause a little more noise. The factory designed with good amount of gear clearance for a reason.

[bigjae46]

Update: car is back together. My clunk has been fixed. Even the M clunk is largely reduced. The poly bushings barely add any NVH. There is a very subtle whine which is awesome. Worth mentioning my shifter is a little bit notchier

There is almost no clunk going from neutral to first or neutral to reverse etc. this was a big issue before and what I thought was M clunk.

Overall very happy with the rebuild

Great news!!!


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[SteelGreyM]

No you're fine. Their shim is conical, so it'll compress when installed and fill the gap as needed.

The other option is to measure the play and get a flat shim that's correctly sized. Accomplishes the same thing in the end.

I was just curious what route you had chosen to go down. Glad to hear your issue is fixed though. Interested in seeing how the diff behaves in the upcoming (tens of thousands of) miles!

I figured I’d be alright. Their solution made sense so long as they did the proper testing which is seems they have.

Me as well! I shouldn’t get so confident as it’s only been a handful of miles so far. But no weird sounds or anything coming from back there. Not that much of a difference at all to be honest. The car just feels… “newer”!!! Which I couldn’t be happier about !

[heinzboehmer]

Free play shim thing.

Should I have measured something? They told me I would be okay and I blindly trusted them.

No you're fine. Their shim is conical, so it'll compress when installed and fill the gap as needed.

The other option is to measure the play and get a flat shim that's correctly sized. Accomplishes the same thing in the end.

I was just curious what route you had chosen to go down. Glad to hear your issue is fixed though. Interested in seeing how the diff behaves in the upcoming (tens of thousands of) miles!

[SteelGreyM]

So did you use the free play fix shim thing from racingdiffs or did you measure the play and buy appropriately sized flat shims?

Free play shim thing.

Should I have measured something? They told me I would be okay and I blindly trusted them.

[heinzboehmer]

So did you use the free play fix shim thing from racingdiffs or did you measure the play and buy appropriately sized flat shims?

[SteelGreyM]

So exactly what had been done or replaced? Clutch stack, side-gears shims, output flange taper bearings? No pinion bearing change?

Only the side gear shims and clutch stack! The bearings I didn’t touch. Probably should have done them while I was there but I got lazy for the first time with this car. (Too much fixing all at once).

[sapote]

Update: car is back together. My clunk has been fixed. Even the M clunk is largely reduced. The poly bushings barely add any NVH. There is a very subtle whine which is awesome. Worth mentioning my shifter is a little bit notchier

There is almost no clunk going from neutral to first or neutral to reverse etc. this was a big issue before and what I thought was M clunk.

Overall very happy with the rebuild

So exactly what had been done or replaced? Clutch stack, side-gears shims, output flange taper bearings? No pinion bearing change?

[SteelGreyM]

Update: car is back together. My clunk has been fixed. Even the M clunk is largely reduced. The poly bushings barely add any NVH. There is a very subtle whine which is awesome. Worth mentioning my shifter is a little bit notchier

There is almost no clunk going from neutral to first or neutral to reverse etc. this was a big issue before and what I thought was M clunk.

Overall very happy with the rebuild

[sapote]

Not sure that would work. The points where the diff bolts thread into the subframe are in front of the rear bushings, so there's no space to move the diff forward with the bolts broken loose..

You're right that the subframe threaded pieces are in front of the diff ears and so cannot push the diff forward.

OP said the bolt head touched the chassis on the way out without any tool on the bolt. Maybe he had non stock extra long bolts.

[cobra]

My wheel hop was caused by too much rebound damping on the shocks, causing them to pack and then alternate between grip and losing grip.

[heinzboehmer]

Break loose the bolts, then remove the front bushing bolt, then I think you can push the diff forward to give more space between the trunk and the rear bushing bolts.

Not sure that would work. The points where the diff bolts thread into the subframe are in front of the rear bushings, so there's no space to move the diff forward with the bolts broken loose.

Also, the hard part is breaking the bolts loose (and torquing them when reassembling). Once they're broken loose, you can use a <insert correct size here> mm box wrench to get them all the way out.

[sapote]

I’m really not sure how you did that as my diff bolts contact the wheel well on the way in/out without the socket on! Very very annoying. I keep a can of undercoating ready just for this job.

Break loose the bolts, then remove the front bushing bolt, then I think you can push the diff forward to give more space between the trunk and the rear bushing bolts.

[bigjae46]

Give yourself at least a week to do the job if you don’t want to rush it and have a bad experience . It is taking me longer than expected. I’m on my 2nd week but had to spend a lot of time waiting for parts.

Oh and remove the driveshaft. I thought I could get away with leaving it connected. For disassembly you can leave it on. But it’s tough enough just to get the diff in by itself I wouldn’t want to mess with lining up the driveshaft too.

Yes. What everyone is saying about the vice is true. Need a good solid one THAT IS BOLTED to a table. You are putting 120lb ft on those carrier bell bolts you do not want it slipping around.

The torque spec for the 14m ring gear bolts is 100nm + 30 degrees. I’ll admit I’ve used an impact to tighten the crown gear bolts. It’s a big Milwaukee battery impact that can certainly get over 100 ft/lbs.

The first one I did took about 2 weeks. I built my 3.91 in less than 3 hours. Didn’t have to mess with the pinion shim.

Be sure to have a new CV gasket.


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[SteelGreyM]

https://www.fcpeuro.com/products/bmw-lubricant-olistamoly-2-ln-584-lo-100g-83190447919

This is the cv joint grease I used. Seems to be the OEM.