What is swap ratio
Figure J: Rear Differential Bolt
E46 DIY Differential Swap
These instructions are only as a guide for people to swap differentials. Please read through all the instructions before attempting to install on your own. I take no responsibilities for any inaccuracies or problems/damage /injuries you may encounter from using these instructions. Please consult your shop manual. Sorry about the poor photos. I wasn’t planning on doing a differential write up. Most of the pictures were taken after I installed the differential. That said… lets begin.
For stock sway bars:
2. Remove bolts holding endlinks. You access these from the top of the upper rear wish bone. The endlink bolt is right behind the spring. (Figure B ) 13mm nut and bolt. (Tightening torque - 25 ft lbs) 3. Remove metal tabs holding the Sway bar (Figure C ). 13mm nut and bolt. Remove sway bar. (Tightening torque - 16 ft lbs )
For Aftermarket sway bars:
1. Unbolt endlinks from the ends of your aftermarket sway bar.
2. Remove metal tabs holding the Sway bar (Figure C ). 13mm nut and bolt. Remove sway bar. (Tightening torque - 16 ft lbs)
3. Remove Exhaust hangers and let it dangle. Unscrew the 2 rubber hangers on the exhaust. 4 13mm nuts (you'll need the room for the next step.) (Figure D )
4. Remove Rear suspension reinforcement brace. There's also a heat shield on the exhaust side held up by 2 10mm bolts. Remove the heat shield first. (Figure E ) The Brace is held down by 6 bolts. Remove the inner 4 13mm bolts first. Then remove the 2 outer bolts, 18mm. (Figure F ) (Tightening torque - 18mm nut 57 ft-lbs, 13mm bolt 22 ft-lbs)
5. Disconnect the drive shaft from the differential input flange. 4 E12 Torx Bolts. (Figure G ) Pry the drive shaft off the differential input flange with a screwdriver. (Tightening torque - E12 Torx bolts 61 ft-lbs)
6. Suspend the right/left axles with a wire/string (Figure I ). Disconnect the right and left drive axles from the differential output flanges. Each
axle has 6 E12 external Torx bolts. (Figure G ) (Tightening torque - E12 bolts 59 ft-lbs)
7. Remove the Differential. Support the differential with a jack. The Differential is held down by 3 bolts. 2 18mm bolts in the front, 21mm bolt on the rear. Remove the 2 front ones first (Figure F). then remove the rear one (Figure J ). (Tightening torque – 18mm Bolts 70 ft-lbs, 21mm Bolt 128ft-lbs) (when reinstalling, insert all 3 bolts finger tight. Tighten the 2 front bolts first, then tighten down the rear bolt).
Work the differential off the car by pulling it towards the rear end. Slowly lower the jack as you pull it out. (you need 2 people for this part.)
8. Since the new differential is off the car. Now is the ideal time to fill up the differential. The drain/fill plugs use a 14mm hex wrench. (Figure A ) It's hard to find. so I used a nut and bolt that was 14mm in diameter instead. Click here for my DIY 14mm hex socket. Use the new seal rings after filling up the differential with new gear oil. (Tightening torque 14mm plug 52 ft –lbs).
Note: I just used Mobil 1 Synthetic 75/90 gear oil since that's what they had at Pep Boys. (oil specification BMW SAF-XO synthetic oil. 0.95 US qt)
Note: Depending on the which car you have and which car your new differential came from, you may need to swap input/output flanges. Here's a post from e46fanatics about the input flange removal/install. (I'll incorporate this into my write up later)
Someone posted a good video showing Output Flange removal / install. Here's a link to his video:
Differential Part #s
07 11 9 963 355 --- Seal Rings for drain and fill plugs
26 11 1 229 536 --- E12 Torx Screw M10x20 (bolts for input / output flanges)
33 17 6 750 780 --- Hex Bolt M12x1, 5x80 (Bolts for Front differential Mount)
33 17 1 094 392 --- Hex Bolt M14x1, 5x133 (Bolt for Rear differential Mount)
31 12 1 092 110 --- Self Locking Collar Nut M14x1,5 (Bolt for Rear differential Mount)Source: www.bokchoys.com