Anyone ever replaced the rear shaft seal in the differential box?

[themysteryman83]

Oil is leaking from the front of my differential, no not a slow leak, it drips everyday from the drive shaft. From what I have read this is pretty common, but now I need to know how easy this is to replace. I have the Bently manual and it really doesn't look too hard. So my questions are: How hard is it to do? How long does it take for a person with moderate knowledge? Is there another way to tell if I have a LSD without jacking up the car and turning the wheels (so I can get the right oil)?

Thanks in advance,

Ian

[cali-ti]

i was going to replace that seal on the used e30 LSD i put into my car and then reconsidered it. you have to get the nut off for the drive shaft flange (i can show you how i was going to attempt to do it if you want) and then retorque it to something like 250 lb-ft when you reinstall it. at that point, i said forget it. you may want to consider having a shop do it or just getting a different diff (LSD if you don't have it). LSD should have a white "S" painted on them as well as an "S" on the metal tag bolted onto the diff (along with the ratio, eg: 3.45S or S3.45 forget which one is used).

[themysteryman83]

Lol, it's so soaked in oil right now I don't even know where the plate is. From what I read in the bently manual, the torque is ~130 ft lbs. Omg if it took 250 it would take the almost the weight of two of me just to break it loose! I wish I had the money for a different diff. I would love to do the e30 one in maybe a 2.93 to get those high rpm's down to a reasonable level. I'm losing a lot of gas mileage because of it too I think. What kind of rpm's do ya run on your 318 with a 3.73??? My top speed is about 108 at 6500!!!

[cali-ti]

guess you're right on the torque spec. it may be higher on the e30 one which i was looking at. the fun part is that the flange spins, you need a way to lock it in place somehow to torque it on/off.

the rpms are about 10% higher that with the stock 3.45 diff. so cruising at around 80mph went from something like 3700 to 4000 RPMs. if you kept the stock 4-cyl and put in a 2.93 diff, your acceleration would be absolutely pathetic, i don't think you'd like it ;)

[J!m]

The easiest way to remove and replace that nut is to use a 3/4 inch drive impact driver.

Use a torque-limiting extension (available from Snap-On or other expensive tool trucks) to put it back on, and soak the threads with red locktite before you put the nut back on.