Transmission output shaft seal, replace.

Support exhaust system
Remove nuts from header flange.
Loosen 13mm bolts on brackets and remove rubber hangers from rear cross member
Remove muffler bracket and lower exhaust from car.
Remove the three 17mm nuts and bolts securing the "Guibo" coupling to the transmission. Leave the Guibo attached to the driveshaft.
Loosen threaded ring at center support. This is best achieved with two large pairs of pliers, apply one set of pliers to the threaded ring (green arrow) and the second set to the weld in the driveshaft tube (yellow arrow). The weld is a rough surface and gives good grip, preventing the pliers from slipping and scarring the tube. It is also the strongest section of the tube. Loosen ring approximately 5 turns.
CAUTION: Do not allow driveshaft to contact fuel transfer pipe between fuel tank halves.
CAUTION: Drive shaft is balanced as a unit, do not separate the two halves without marking them for correct re-assembly.
Tie drive shaft out of the way, in such a manner that no stress is put on the center universal joint.
Pry out locking ring on output shaft nut (if fitted). This ring is not to be re-used, it will deform on removal.
Place transmission in gear, remove nut with a slim walled 30mm socket. If necessary, stop flange from turning with large "water pump" pliers.
Slide output flange off shaft by pulling evenly.
Pry out old seal with a seal remover or screwdriver.
CAUTION: Take care not to damage splines on output shaft, or gouge aluminum seal housing during removal.

Installation:

Install new seal evenly in housing with edge of seal approximately 1mm further out than original seal. This will prevent the sealing lip from running on the same section of the output flange's machined surface.
Clean threads on output shaft and inside nut, apply a liberal amount of Loctite 270 or equivalent thread locking compound.
Note : Do not install the locking ring. This requirement was dropped by BMW when instructions were issued to use Loctite on the threads instead.
Replace gasket and nuts at exhaust manifold flange. Use copper nuts.
Install manifold nuts and muffler bracket, and tighten to correct torque before installing other mounts.
Correctly positioned exhaust must have tailpipes in center of opening in rear valance.
Install rubber hanger and bracket at rear sub-frame and position bracket so that rubber hanger has slight tension only.

Torques:
Flange nut	:	Step 1 : 170 Nm (123 ft lbs.) Step 2 : Loosen Step 3 : 120 Nm (87 ft lbs.)
Center support :	:	22 Nm (16 ft lbs.)
Guibo :	:	10mm 8.8 bolts, 46 Nm (33 ft lbs.) ; 10mm 10.9 bolts, 72 Nm (52 ft lbs.) ; 12mm bolts, 123 Nm (89 ft lbs.)
Rear flange to differential :	:	72 Nm (52 ft lbs.)
Threaded sleeve :	:	17 Nm (12 ft lbs.)
Pipe to manifold	:	Step 1, 30 Nm (22 ft lbs.) Step 2, 50 Nm (26 ft lbs.)
Muffler brackets	:	14 Nm ( 10 ft lbs.)
Hanger bracket to rear sub-frame	:	22 Nm (16 ft lbs.)

E30 M3 Repair Manual V2.7. Copyright Š1999-2001 Koala Motorsport & Brett Anderson