txag_530i

You have to remove the fill plug and suction out the old fluid with a fluid extractor (like the Mity Vac Fluid Evacuator) or simple hand-pump. You replace the fluid in the same fashion. There's no other way to do it without dropping the rear axle to get the differential bolts clear of the back frame of the car. Fu%^&*g brilliant design from BMW.

txag_530i

If the drain is on the bottom of the device then how do you propose to get the replacement fluid to the correct level?

gcalo

I have designed a plug for the drain that will have a center portion that turns to open w/in the differential, has a 1/4" hose connection, and it will enable one to pump in 2 qts of 75W90 Redline (or whatever determined fluid), turn to close, and that's it.

Going to our machinist who makes all our parts for our license plate holders

Piece of cake!

gcalo

Measure what comes out after the draining.

It should be about 2 liters.

Replace with the same amount.

Booyaazaa

How's the plug coming?

gcalo

Have the design done.

Refining a few small issues then it goes to machinist for samples

best1

My diff is leaking at both half shafts. Looks like I will get new fluid.

gcalo

That is a bummer.

Sounds like your seals have gone bad.

All the more reason to change the oil regularly.

best1

i changed it at 80K. now at 113K. Indy said it is a common problem on these cars.

gcalo

I am very lucky then because at 114,800 miles my underside is dry.

No leaks on diff either