DIY Question: Rear Differential Seal Change

I have a 2005 BMW 325i Automatic. I was working on replacing the rear differential seal when I came to the nut that holds it in and couldn't find the right size socket and/or the socket walls weren't thin enough for clearance. If that doesn't sound right or I need a special tool please let me know. Luckily it's a slow leak and not too high on my list of repairs so I can let it go for just a bit. Your input would help. Thank you.

-Noob

are you talking about the input shaft seal, output shaft seals or diff cover gasket? I have a feeling you are talking about the input shaft, if so that takes a thin walled socket. can be bought at sears, it also has a locking washer around the nut. Furthermore, if you take off that need to be put on exactly the same tension/torque as before or you'll damage the pinion/ring as it'll knock them out of alignment/sync and cause the diff to go out.

what number seal? 10? http://www.realoem.com/bmw/showparts...85&hg=33&fg=05

i have a similar leak with my rear differential. do you have a link to the part number or where i should look for it on realoem for the real mail input seal? (2002 325xi). is it part #7? http://www.realoem.com/bmw/showparts...61&hg=33&fg=10

Originally Posted by wdeerfield

i have a similar leak with my rear differential. do you have a link to the part number or where i should look for it on realoem for the real mail input seal? (2002 325xi) thanks much.

do you mean "rear main" ?

Originally Posted by Alex323Ci

are you talking about the input shaft seal, output shaft seals or diff cover gasket? I have a feeling you are talking about the input shaft, if so that takes a thin walled socket. can be bought at sears, it also has a locking washer around the nut. Furthermore, if you take off that need to be put on exactly the same tension/torque as before or you'll damage the pinion/ring as it'll knock them out of alignment/sync and cause the diff to go out.

what number seal? 10? http://www.realoem.com/bmw/showparts...85&hg=33&fg=05

Yes. The Input Shaft Seal. #10 as you listed it. It matches with the part number that is on the bag. You said a thin walled socket at Sears. I did not get the size of the nut. Would you happen to know? As for the torque, how do I know what it is/was/will be? I do not have the Bentley Repair Manual yet (Yes. . . feel free to laugh) as I'm doing repairs.

look in the DIY section of the forum. should be an Diff Input Flange diy listed. the way you reset the nut torque is to make a mark on the nut and tip of pinion shaft next to each other. count the revolutions exactly that it takes to remove. after the new seal is on, re-install the nut the exact same number of turns and back to the matching marks on the nut and tip of shaft. make sure the locking ring/nut is back on and bend in to keep from coming loose.
so what you are doing is putting it back on the exact amount of threads and spot it was before you took it off.

Originally Posted by Alex323Ci

do you mean "rear main" ?

Yes, sorry. Rear Main Seal where the driveshaft bolts up to the rear diff.

Originally Posted by Alex323Ci

look in the DIY section of the forum. should be an Diff Input Flange diy listed. the way you reset the nut torque is to make a mark on the nut and tip of pinion shaft next to each other. count the revolutions exactly that it takes to remove. after the new seal is on, re-install the nut the exact same number of turns and back to the matching marks on the nut and tip of shaft. make sure the locking ring/nut is back on and bend in to keep from coming loose.
so what you are doing is putting it back on the exact amount of threads and spot it was before you took it off.

This is what I found. Before you read on, does 30mm thin walled socket sound right? Other than that the procedure seems straight forward. I'll wait for your reply on the pinion nut size before I start.

Procedure:

1. Determine the "spinning torque" prior to disassembly. Run one of the driveshaft-input flange bolts into the input flange until it bottoms out. Use a stack of washers or a socket under the head of the bolt if it sticks through the flange too far. Use an in-lb or in-oz dial torque wrench and the appropriate sockets/adapters to see how much torque it takes to keep the pinion (and the rest fo the diff guts) spinning once started in motion. Ignore the initial spike in torque and watch for the constant number after the spike. Write down that value on the side of the diff case. Do the same thing for both your old diff and the new one. You should put the new flange on the old diff so the next guy an use it.

2. Pry out the pinion nut lock plates and remove the nuts (30mm socket). To keep the flange from spinning, have a buddy thread a couple driveshaft bolts into the flange and counter with a pry bar. Keep the nut with its original diff.

3. Pull off the input flanges. The flanges will come off with hand pressure. If not, use a rubber mallet. A 10 ton 3 leg puller is not necessary.

4. This is a good time to replace input flange seals if necessary.

5. Put your original flange on your new diff with the new nut using Loctite 272 (high strength, requires heat to remove). Snug it down and check the spinning torque. If the spinning torque is low, tighten the pinion nut a little more and check again. Repeat until the spinning torque is correct. DO NOT OVERTIGHTEN THE PINION NUT. Overtightening causes the crush sleeve to crush too far resulting in either overloaded bearings or insufficient pinion nut torque and a loose input flange. You will have to replace the crush sleeve and start over.

6. Install a new pinion nut lock plate. Use a socket or punch to drive the plate all the way down. Stake the lock plate into the grooves to keep it fom spinning.

7. Repeat steps 5 and 6 using your old diff and pinion nut and new flange.

I also came up with this:

I had already taken the input out to replace the leaking seal before I came to the revelation that I should have consulted my Bentley book before hand..
Once opened I then learned there is NO indication as to what the torque spec could be or information about the spinning tq to establish proper spec.

Bentley is stating to dike mark both the nut and input pinnon surface to properly reinstall nut to spec. I hope the tread count was the same, (still this was an after thought on my part, to late.)

I read on a different site someone indicated about 11-14 inch-lbs is a good start.

bump for clarification of rear main seal part.. thanks.
http://www.realoem.com/bmw/showparts...61&hg=33&fg=10
is part #7 what i should replace for a leak in the front of the rear diff?

Originally Posted by conkelid

This is what I found. Before you read on, does 30mm thin walled socket sound right? Other than that the procedure seems straight forward. I'll wait for your reply on the pinion nut size before I start.

This is what I did:


Tools:

a) 1 1-1/4" 1/2 drive socket (or 30mm)
b) Flat screw driver
c) Slidehammer

1) After removal, I marked the front nut and pinion with Red paint to re-align correct position upon re-install and proper torque so that I wouldn't damage crush collar

2) Pry over the lock ring tabs on front flange with a med screwdriver.. remove with needle nose pliers.. I had a airgun avail, so I simply removed the front 30mm pinion nut (if you don't have avail loosen this nut while diff is still in car with handbrake on after fr driveshaft removal)

3) Gentle tap with a hammer and woodblock front flange will slide off, also have a rags avail as diff fluid will leak

4) Perform same on new differential as described. Re-torque front nut to line up with the red marking you make prior to removal.. then install a NEW lock ring and peen the edges over to secure

Originally Posted by wdeerfield

bump for clarification of rear main seal part.. thanks.
http://www.realoem.com/bmw/showparts...61&hg=33&fg=10
is part #7 what i should replace for a leak in the front of the rear diff?

Yes. I believe this is the same part. If you look earlier in the post for my model and yours, the #7 on yours and #10 on mine are the same part number, the Rear Differential Input Seal, listed as "Shaft Seal". The stealership reviewed mine during a service and said the "Differential Seal" was leaking and needed to be replaced. Parts said, and when I checked later, verified that specifically the "Input Seal" was the culprit. I was told that that was normal for that seal to wear and need replacing. Hope this clarifies.

Please Review and Compare:
Yours: http://www.realoem.com/bmw/showparts...61&hg=33&fg=10
Mine: http://www.realoem.com/bmw/showparts...85&hg=33&fg=05

Originally Posted by lkstaack

This is what I did:

Thanks for the information. I'm due for this repair in early February. I'll give this method a try as it seems pretty simple, and that's good for me and everybody.

Originally Posted by lkstaack

This is what I did:



3) Gentle tap with a hammer and woodblock front flange will slide off, also have a rags avail as diff fluid will leak

Very helpful.

How about avoiding this need for rags by draining the differential fluid first and refilling with new fluid when you're done with the seal replacement?

DIYs for fluid change are online. Pretty simple to remove drain plug and fill plug. DIYs cite 75W90 synthetic gear oil for non-M3 (non-LSD) e46.

Originally Posted by kbok

How about avoiding this need for rags by draining the differential fluid first and refilling with new fluid when you're done with the seal replacement?

Wow! Why didn't I think of that?

Actually, it's still going to leak out when you pull it....draining the oil doesn't get every last bit out.

How serious a problem is a front differential leak? I had a shop notice it when I got new tires. Should I get it fixed immediately. Thank im a noob