[Polo08816]

Originally posted here: http://f30.bimmerpost.com/forums/sho...1#post21441541

This is write-up is not meant to be a complete standalone DIY. This is just bits and pieces of advice/suggestions I have for the DIYer when following the ISTAD procedures pdf I posted in Post #145. I recommend doing this procedure with the help of another person. My girlfriend is awesome because she wakes up at 5am on Sundays to help me out on these installs.


I finally received all the tools after 2-3 weeks since the special Torx socket needed to be shipped from Germany. All special tools and parts came from getBMWparts. They were extremely helpful in translating BMW tool numbers to part numbers.


Pry-bar of Thor. BMW Tool # 33 5 120. BMW Part Number 83300495851. This is required for the removal and install of the rear differential. I haven’t come up with an alternative way around (as laid out in previous posts) so I dropped some coin on it. BMW went away from the bolted output shaft design so this special tool is now required.




Here’s how the BMW M Performance Limited Slip Differential came:



It comes with a new insert nut so you don’t need to order the repair kit when ordering this differential.


First off, remove the exhaust system and remove the heat shields as performed in Post #145.


Next, disconnect the propeller shaft. I supported the propeller shaft with two jack stands. I then slackened (not fully removed) the two bolts holding the center universal joint (bearing). I secured the propeller shaft against rotation by inserting a screw driver through the u-joint. Usually this is not recommended, however, the BMW ISTAD Rheingold specifies this as an acceptable way to brace the propeller shaft. My guess is that there’s sufficient resistance already since the propeller shaft remains bolted to the transmission.




Then, open the insert nut which connects the propeller shaft to the rear differential. I used a HP Autowerks differential tool for this step. The insert nut must be opened in a CLOCKWISE direction. The insert nut is opposite of normal tightening/loosening directions.




Propeller shaft disconnected from the rear differential.




Remove the rear vibration damper. Removal on my car required a special Torx E10 socket (BMW tool # 2 240 515 and part number # 83302240515)


Now support the differential using a transmission/differential jack. The jack I used wasn’t the best. The chain used to secure it didn’t secure it that well, so I would recommend 1-2 ratcheting straps for someone doing this in the future. The reason is because you will need to tilt the differential to remove and install the output shafts.



Make sure you strap it down between the final differential (back) cover and axle shafts.




Now remove the left (passenger side) output shaft based on the ISTAD Rheingold procedure. You won’t be able to remove the right (driver’s side) output shaft just quite yet. The rear differential mount blocks you from getting a good point of leverage using the special pry bar from the right side.






Use jerky movements and the output shaft will eventually pop out.




Now that you have pressed out the left output shaft, you can release the two front differential bolts using an 18mm socket and breaker bar. This is a long bolt so once you have it loosened, you can go ahead and use an air ratchet to remove it. Make sure you’ve properly supported the differential with that transmission jack.




Remove the rear bolt. There is a nut on the back of the bolt which needs to be replaced. You’ll need to use a breaker bar to secure the nut against rotating with the bolt when you are trying to remove it. I believe they both were 21mm.




Now lower the rear differential.




Pry out the right (driver’s side) output shaft. This one gave me heartache because I could not find a good place on the actual differential to use as a leverage point for the special pry bar. I ended up needed to reinsert the front and back differential bolts and then pressing against the transmission jack to pop out the right output shaft.




Stock open rear differential finally lowered.




Place the new BMW M Performance Limited Slip Differential on the transmission jack and secure it using chain/ratcheting straps.






Unfortunately, I missed a lot of photos at when trying to get the output shafts into the new differential. This was the toughest part of the job in my opinion. The steps I took were different than what is written in ISTAD Rheingold. The steps I took were roughly in this order:

1. Raise differential on transmission jack.
2. Feed right (driver’s side) output shaft into differential.
3. Brace differential against rear subframe. This was done because tapping the special pry bar accessory – the BMW cinching device – with a rubber mallet wasn’t seating the output shaft back into the differential. In retrospect, I could have done a better job of aligning the splines of the output shaft to the grooves in the differential by simply rotating the output shaft until it fit better.
4. Tap right output shaft into differential with rubber mallet. Don’t use a metal hammer. If the splines and teeth are not lined up correctly, tapping the cinching device with a metal hammer may damage the output shaft and rear differential.
5. Lower the differential and turn it so that the left output shaft can be fed into the differential.
6. Feed left output shaft into differential.
7. Raise differential back up into the subframe to a position where you can re-insert the front and rear differential bolts/nuts. Screw in a few threads in so that the differential won’t move. It is now braced.
8. Tap the left output shaft into the differential using a rubber mallet.

Now insert the front and rear differential bolts/nuts but do not torque down yet.
Release the chain/ratcheting strap.




Lower your transmission jack. Differential should be in position.




Now it’s time to connect the propeller shaft back to the differential. Once you start to screw the insert nut in, you have approximately 5 mins to complete this procedure. I don’t have many pictures for this portion of the install but here are the rough steps I took:

1. Slide propeller shaft to the limit position onto insert nut.
2. Fasten the insert nut to propeller shaft by going in a COUNTER-CLOCKWISE direction.
3. Insert center universal joint bolts and screw on a few threads.
4. Torque down insert nut using HP Autowerks differential tool at 85 Nm.
5. Torque down center universal joint bolts to 19 Nm.

Picture of final install:



Reinstall heat shields and complete exhaust system.



Total time for my install:
6 hours
I don’t think I could ever get it down to the 2 hours spec’d for dealers in BMW KSD. I think if I were to do it again, I could do it around 3 hours.


Initial review of the differential:
It's awesome compared to the stock open differential. When you're accelerating hard out of a turn, you can hear the clutches working and no DSC/traction control intervention to be found. I can't wait to experiment with this at some HPDEs this upcoming season.