I drove my sleepy self to the Auto Crafts Shop at a nearby military installation at 7am in the morning. BRRRR! It was 11F. I was the first (and only) person to arrive around 7am. Yes, I know… I’m crazy… or so I’m told.
I had the opportunity to do a more thorough reconnaissance of this rear diff removal/replacement procedure this weekend. This is a partial dry-run for a future diff swap. I’m still deciding between the BMW M Performance Limited Slip Differential (LSD) and another aftermarket clutch based LSD. In the end, I probably see myself going with the BMW M Performance LSD. I will probably keep the original final drive in case I would like to use it as a core unit for aftermarket clutch based LSD in the future.
Swapping out brake pads (equipped with M Sport Brake Option)
I began by swapping out F80/82 M3/M4 brake pads (OEM - Textar) for my original M Sport Brake Pads (OEM - Jurid). It’s been getting colder and I prefer to have a bit less brake dust in the months when I’m can’t wash the car outside as often. Brake fluid remains the same with Castrol SRF.
I’ll miss the better feel of the M3/M4 brake pads. It feels more linear and provides greater braking force at higher speeds, but they’ll be back in action sometime in the spring in anticipation of more AutoX and HPDEs. I always use Permatex Ceramic Extreme Lubricant and never have an issue with noise with hotter/more abrasive pads if applied properly.
Now we begin to remove components to get better eyes on the entire propeller shaft… I simply followed the procedures in the PDF I have attached with this post.
Removing center chassis reinforcement plate.
Removing the complete exhaust. I’m not a fan of cutting the exhaust so I decided to remove the complete exhaust. You’ll need another person to help you (my GF who has a 2016 X3 35i). You’ll also want to have 2 jack stands to support the exhaust.
Slackening (and then eventually removing) center exhaust mount. Requires E10 socket (Inverted Torx bit)
Slackening (and then eventually removing) mounting brackets at axle back (muffler) section.
Loosening the V-band that mates/seals the downpipe to the catalytic converter section of the complete exhaust system. This takes a bit of effort as the bolt and nut are heavily rusted. This is normal. I was able to do it with a standard 3/8” drive ratchet. You cannot re-use this part. It’s one time use which means you better seat it properly when you are re-installing the exhaust.
Exhaust removed.
Once you remove the exhaust, remove the heat shields. You can probably do the LSD removal/install by removing the heat shield furthest to the rear, but I removed both heat shields because I wanted to get a good look at the transmission, transmission mounts, flexible disc, and forward portion of propeller shaft as well.
Front section of propeller shaft.
Close up of transmission (ZF 8HP45) mounts and flexible disc which connects the transmission and front portion of the propeller shaft. They seem to be in excellent condition considering my car has 72,000 miles on the odometer.
Center mount and central section of propeller shaft. When removing the propeller shaft from the rear diff, you’ll need to pay particular attention to the installation and bolt tightening sequences. I believe you will slacken (but not remove) the center mount in order to allow the propeller shaft to belt slightly at the joint, but be careful not to bend it too much or else it will damage the propeller shaft.
ISTAD also says when you need to tighten the insert nut where the rear differential and propeller shaft meet, you will need to brace this so that it does not rotate when you are torqueing down the insert nut. I suppose BMW wants you to place a small metal shaft through the joint and brace it against the chassis. I was initially wary of doing this as it might damage the joint, but I tried to rotate the propeller shaft (parking brake disengaged) and it didn’t budge. Perhaps there is already sufficient internal resistance with respect to the propeller shaft, rear differential, and transmission that the specified bracing method is acceptable.
And we’re finally to the most important part… the rear differential.
Remove the vibration absorber at the rear of the rear differential/subframe mount.
Disconnect the propeller shaft. HP Autosport makes a tool to remove the insert nut with a 1/2" hole. It allows you to place/connect a 1/2" drive torque wrench. The BMW specified tool doesn’t have this functionality.
Release the center mount that you previously slackened.
Tie up propeller shaft to somewhere. Don’t bend the propeller shaft excessively.
Now you need to remove the output shafts from the rear differential.
Here’s a CV axle tool from BavAuto that will probably work in removing the axles.
But the main issue is pressing the output shafts back into the rear differential. With this new BMW design, there’s nowhere on the output shaft to tap to put it back into the rear differential. They require you use a special tool that costs about $400.
Here’s few pictures of the rear differential in place.
While I was in here, I wondered how much work it would be to replace the rubber mounts/bushings for the rear differential. There are 3: 2 front and 1 rear.
Front side of rear differential with 2 rubber mounts.
The front rubber mounts/bushings aren’t bad. They require a special tool. You can find these in the attached PDF.
The rear rubber mount is the one that may require a lot of work. ISTAD Rheingold lists dropping the entire rear subframe in order to replace this rubber mount/bushing. I was scouring the internet to find any tool that would be able to remove/install this rubber mount/bushing without having the drop the rear subframe. I’ve found some similar tools at Koch Tools and Baum Tools. Unfortunately, they stated they were designed for larger F-chassis BMWs such as the 5, 6, and Series. I wondered why these chassis vehicles did not require removing the rear subframe. Well, based on what I saw today, it would appear as if the fuel tank prevents a tool from either withdrawing or installing a rubber mount/bushing due to limited distance. See fuel tank at the top portion of the picture.
That's it for now folks...