E90 BMW 335i to M3 Differential Swap

By Michael Lampton / Engineered Mechanic Mike

https://www.facebook.com/engineeredmechanicmike

Disclaimer!!!

Follow this guide at your own risk. I am not responsible for any damage to your vehicle. Always use safe

practices when lifting, supporting and working on your vehicle. This is meant solely as a guide for how

the swap was completed and is open to interpretation/deviation based on your setup. All work was

completed on jack stands without the use of a lift.

Now would be a good time to replace the differential bushings as the 335 bushings are weak

compared to the M3 bushings or aftermarket ones like PowerFlex.

Tools Used:

Sockets (mm) (Good to have deep and shallow): 8, 10, 13, 17, 18, 21, (36mm 12point for axle

shafts)

Wrenches (mm): 18, 21 (normal box end wrenches and gear wrenches)

Specialty Sockets: E12, E14 (Shallow and Deep)

3/8” and ½” Ratchets

Multiple jacks and jack stands

Variety of extensions and wobble adapters

Air tools: ½” impact, air hammer

Various pry bars

Bearing separator tool

Step 1: Raise and support the vehicle on level ground so all 4 wheels are off of the ground.

Step 2: Remove the exhaust from the catbacks to the muffler. Remove the two heat shield pieces that are

covering the driveshaft.

Step 3: Before removing the driveshaft, you must measure the length as shown below. The measurements will

not be the same for two cars so do not use someone else’s measurements. You will need these

measurements for when getting the M3 driveshaft reworked.

The 335 transmission end flange from the driveshaft will need to be cut off and welded onto the M3

driveshaft. The M3 driveshaft will also need to be shortened and balanced. Lastly the center bearing

from the 335 will need to be swapped over to the M3 drive shaft. This will be shown later on.

Pictured below is where you should take measurements of your current setup to then compare to the

M3 setup. You will need to measure from hard fixed points since both drive shafts have the ability to slip

forward and back.

1. Measure from the differential mounting flange edge to the center bearing flange edge. The

distance from the differential flange face to the center bearing needs to be the same for both

the 335 and the M3

2. Then, on the 335 shaft, measure from the forward edge of the center bearing flange up to the

transmission end of the driveshaft flange. The distance from the center bearing to the

transmission end of the flange on the driveshaft will vary based on car model. When you get the

M3 driveshaft reworked, you will need to give them the measurement you took here.

Step 4: Unbolt the driveshaft from the transmission end. I used an 18mm box end wrench on the nut and an

impact with an 18mm socket on a wobble. You will need to be able to rotate the driveshaft around to

reach all of the bolts. You only need to remove the 3 bolts that hold the drive shaft to the rubber flex

disc.

#1

335 Differential and Drive

Shaft

M3 Differential and Drive Shaft

#2

Step 5: Unbolt the drive shaft at the center bearing from the body of the car. The bearing is retained by two

13mm bolts.

Step 6: Unbolt the axles from the differential. These are retained by six E12 bolts on each axle.

Step 7: Using a suitable jack support the differential prior to unbolting it. The differential is bolted to the rear

sub frame using two 18mm bolts on the front and one 21mm bolt and nut for the rear. Using a 21mm

wrench and a shallow 21mm socket, remove the rear differential mounting bolt. Then with an 18mm

socket, wobble, and extensions, remove the two 18mm bolts. Once all bolts have been removed, the

differential can be lowered.

Differential removed. Front bushings and rear bushing for differential.

Step 8: With the differential and driveshaft out of the vehicle, set it up side by side with the M3 differential and

driveshaft. Begin by recreating the measurements you took of the 335 and then comparing that to the

M3. Reference Step 3 above.

Step 9: Remove the front tube half of the 335 driveshaft. This is done simply by pulling the rubber boot off of

the tube and pulling the shaft off of the splined yoke.

Step 10: Using a bearing separator tool, remove the center bearing from the 335 driveshaft. This should come off

fairly easily with the proper tool. Remove the rubber boot first will help as well as it is not used again.

Pay attention to the forward direction of the bearing. Mark it with an arrow for the forward direction.

Step 11: On the M3 driveshaft, there is an 18mm bolt that is holding the two drive shafts halves together. Using

an 18mm gear wrench, remove this bolt. Once the bolt is removed the front tube shaft can be slid off of

the yoke.

Step 12: The center bearing on the M3 driveshaft pulled off easily but may require the use of the bearing

separator tool.

Step 13: Install the 335 center bearing onto the M3 drive shaft. Ensure that you reinstall any thin washers used

and the correct orientation of the bearing. Reinstall the front tube half. Install the 18mm bolt as well.

Step 14: Take the M3 drive shaft assembly and the 335 front tube half to a drive shaft shop. It is worth noting

these tubes are hollow and the flange ends are friction welded. This may scare off some driveshaft

shops. First shop we went to couldn’t help. The second shop said not a problem and their solution was

to cut both shafts and mill the 335 flange down so it could slip into the M3 tube and then be welded

after that they balanced everything. See the pictures below.

335 shaft with flange removed

M3 flange removed

M3 shaft with 335 flange installed

Step 15: Remove the rear wheel. Remove the axle nuts using a 36mm 12 point socket. I recommend using a

really strong impact, but a suitable 1/2'” breaker bar and a pipe should do the trick. You will need a way

to keep the axle from spinning. The parking brake may be strong enough to so this but you can always

put a screw driver in the slot of the rotor and use the caliper bracket to keep things from rotating. The

axle nuts are “locked” into place by damaging the outer ring so it bites into these notches on the axle.

Use a chisel and hammer to bend these out of the way. It will be very hard to do, so take your time.

Otherwise you will be fighting these when trying to remove the axle nut.

Step 16: Once the axle nuts have been removed use both a very strong drift punch and heavy 5 lb. hammer to

drive out the axle from the hubs. These will be stuck in there pretty good so it will take some time. I

used an air hammer and it still took some effort. You might try using some penetrating solvent to help

free up any rust in the area too. With the differential out of the way this makes getting the axles out

very easy. This eliminates the need for removing any suspension pieces or the rear hub from anything.

Step 17: Install the new M3 axles. Grease the splines before installing the axles to ease with installation. Below

shows the difference between the 335 axle and the M3 axle. You cannot reuse the 335 axles as they will

not fit the M3 diff hubs. I suggest getting new axle nuts as well. Ensure the axles are fully seated into the

hub the axle nut is properly tightened down.

Step 18: It is now time to install the M3 diff. Using two jacks, support the base of the diff with one jack and use

the other to support the pinion of the diff. Use both to raise the diff into place. Reconnect the axles to

the diff at this time. It will be easier to do now as you can move the diff around prior to it being bolted

to the sub frame. The axle bolts are bigger than those of the 335 so you will need to get the right size

hardware for the axles. Use an E14 socket to install the axle bolts to diff. Lift the diff into place. Install

the front and rear bolts for mounting the diff.

Step 19: Install the drive shaft to the diff first. Install the front of the driveshaft into the output of the

transmission and bolt it back to the flex disc. Mount the center bearing back to the body.

Step 20: Reinstall the heat shields. The rear heat shield may need to be trimmed or completely left off in order to

clear the diff and drive shaft. Reinstall the exhaust and any under body panels. Reinstall the rear wheels.

Safely remove the jack stands and lower the car to the ground. Go for a test drive and enjoy!