E28 Diff install DIY

[Bluebimma]

Disclaimer:
Follow my instructions at your own risk. I am not liable for any damages caused by following my instructions. Proceed at your own risk.

Please read before tearing your car apart and make sure you have everything needed for the swap. The E28 differential swap is the same as installing an E30/24 differential into the E36 compact chassis.


Supplies needed.
E28 Differential
E30 ABS axles and studs or (optional unless lowered)
E36/5 Output Flanges
E36/5 Output shafts
For any medium case diff install on the E36/5, you will need a ///M Coupe, ///M Roadster, any Z-series 6cyl plate or E30 (6cyl.) medium case differential plate. Z3 1.9 and small case differential plates from the E30 318 and m3 do not work with this upgrade. (This is essential to mount the diff to the car since the E28 doesnt have the same mount point)
New locking circlip for the output flanges
2qts of Part# 83 22 1 470 080 from the dealer or an equivalent blend of gear oil with Posi additive
Standard Mectric tool set with 10-19mm, rachets, a breaker bar, open end wrenches, a pipe to use as a breaker bar if you dont own one which can be used with your rachet and wrench, shop towels, gloves, jack stands

Gear ratio file:
http://www.fileden.com/files/2007/1/...ial%20Tony.xls

[Bluebimma]

Your diff may sound like this if the gears have sheared themselves.

[Bluebimma]

First jack the car up. Secure the front wheels from rolling. Stabilize the rear end if working in your garage, etc.
Remove exhaust if needed. I took mine off to be replaced anyways.
The driveshaft to input flange uses a locking nuts which needs to be replaced when done. These require a 16mm wrench and a pipe if you need more leverage to break them loose. Put the gearbox in 1st gear and lock the e-brake so the driveshaft doesn’t spin. Unlock to move on to the other bolts. It really helps to have someone else there to lock and unlock the gearbox/e-brake. Once you remove these, move to the next step.

Next, mark your axles to the output flanges before you unbolt them. The bolts that attach these to the output flanges are male star heads, 10mm. There are a total of 12, 6 per side. Remove those and hang the axles up to the chassis using wire or some other method.


I used a jack to lift the diff just a smidge to get at the next set of bolts. There are two top bolts that require a 19mm wrench and possibly a pipe to break loose. These are a total pain, so stick with it. Once those are removed, go down to the next two bolts at the mid/lower half of the diff, these are also 19mm, but you can easily get a socket and wrench on them.


Next is the last bolt which is the mounting plate bolt and nut. Make sure your diff is secured on a jack or whatever you’re using to lower it from the vehicle, use [2] 19mm sockets and wrenches to unbolt the nut and bolt.
Once unbolted, the diff can now be dropped from the chassis.
While out, there are many things you can and should want to do. You can paint your new diff, the cover, change gaskets, clean the diff, clean the underside of the car, replace bolts, etc.

You will reuse your gear speed sensor, so unbolt that from the old differential, clean it, and install on the new one. Test fits indicate that the fill/drain bolts are interchangeable for the 318Ti, ///M Coupe|Roadster, and E28 differential plates; not sure about the e30 bolts. You will need a new gasket for your E28 diff to diff plate surface.

Installation is the reverse of the removal. When installing the new differential, lift the differential into place and bolt the TOP two bolts first for alignment. You will have great difficulties realigning the new differential if these arent aligned first. Next is the two bottom bolts, then the rear differential plate mount.

[Bluebimma]

Differential diagram.



E28 Limited slip unit.

[Bluebimma]

///MCoupe/Roadster Finned Differential Mounting Plate
33-11-2-228-335-M9

///Mcoupe Differential plate mounts and aligns perfectly with Medium Case differentials. NOTE: Rear driveshaft was removed due to other complications, this is NOT required for the differential swap.




E28 Output Flange on the left, E36 Compact on the right. There is a difference in length but nothing to be worried about. You must use the E36 compact output flanges if you wish to reuse the E36 compact axles. They will NOT bolt to the E28 flanges.

[Bluebimma]

Pictures of a blown differential.

Diagnosis: Damaged 3.45 Input causing excessive damage to Output gear.

[Bluebimma]

E28 Differential installed.

3.45 to 3.25 is a 300rpm drop in over stock meaning, @80mph youd do 3,800rpm with the 3.45, the 3.25 rolls it at 3,500rpms.

After said and done, enjoy your new Limited-slip Differential.

[thesk8nmidget]

Very nice write up.

One thing though. You do not need a different mouting plate. But it would make it a little easier to line all the nuts and bolts up.

Do you have the part number for the diff cover?

[Bluebimma]

Im not done with the diy yet. Youre saying the 1.9 mount plate and medium case diffs are the same size/bolt on?

I checked it out and compared, theyre by no means the same and the 1.9 mount plate will NOT bolt to an e28 different. None of the holes are lined up.

[Bluebimma]

33-11-2-228-335-M9
MCoupe/Roadster Finned Differential Cover
Pelicanparts.com

[thesk8nmidget]

thanks!

[Bluebimma]

Re-edited for final write up, good luck guys and gals!

[Phamster]

Nice! Thanks for the write up.

[FATHER]

i install mine with TI flanges and shaft, i used 2.93lsd, what ratyio you install??

[ATF]

I believe the blown one was a 3.45, He replaced it with a 3.25

Hey Tony,
Did you cuddle with that thing in bed before you put it in? Lying on the garage floor with the thing, getting all dirty.. like it's your baby

Nice write up.