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Faults, Fixes and DIY Please share your experience and knowledge with other members by contributing your own DIY, or by helping another member find the elusive fix!


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Old Mon, May-24-2010, 10:15:41 PM   #1
jcreme
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Default Rear Differential input seal replacement

This will take you about a day.

For my '03-1/2, stuff I couldn't do the job without was:
- 12mm hex socket (allen) for the diff drain plugs
- 32mm (or 1-1/2") socket for the input shaft lock nut
- 550 ft-lb impact wrench
- 1.3 L of 75w90 gear oil. I used Mobil 1 that I found at Auto Zone for $15/L. At Advance Auto Parts (after my purchase, unfortunately) I found Royal Purple for about the same price. Or use the stuff from the stealer if you want to feel rich. At the same time I bought a $4 hand pump which made refilling waaaaaaay simpler and cleaner.

EDIT I later ended up using BMW oil. The gizmo that makes the diff a limited slip needs the extra lubriciity additive in their oil. If you don't use it, you will get a noisy choppy diff.


In addition to the impact wrench, the pneumatic wrench will save you at least a couple of hours' work.

1. Get the car up on jacks

2. Remove the rear suspension reinforcement brace
that bolts to the car near the rear jacking points and the subframe support.

3. Remove the rear section of the exhaust
between the muffler and the resonator. I thought I could get away without doing this and had to take it off later anyway AND it will make the job faster and easier.

4. Remove the silver exhaust heat sheild that runs down the drivetrain tunnel.

5. Remove the rear suspension/subframe support.
a. First remove the little heatshield over the driver’s side subframe bushing
b. Remove the four bolts that hold on the support and remove the support. Keep in mind that this is the rear lift point of the car, If you need to move it mid-job, this needs to go back on.


6. Now is a good time to drain the differential. You probably could use a break by now anyway. Loosen and remove the two 12mm allen bolts on the right side of the diff (the lower is the drain, the upper is the fill) Torque on these is 44ft-lb if you have o-rings or 48ft-lb if you have a sealing washer. Let it drain for 30 minutes are so. Great directions are here.

7. Undo the six torx bolts that hold the drive shaft to the input flange (retorque to 63ft-lb). I couldn’t find the proper socket, so I used a regular 10mm socket. The aren't super tight , so it’s no big deal. Mark the input flange and the driveshaft flange so you can locate them back together in the same way.


8. Once the bolts are out, use a large screwdriver or small pry bar to seperate the input flange from the drive shaft. There is notch on each side of the assembly just for this.


9. I used a small prybar to pry/wiggle the driveshaft out of the input flange. The parts in this area are hardened steel, so they are nearly impossible to damage, but be carful anyway. The flex in the rear diff mounts is juuuuuust enough to get it out. Remove the nuts that hold the driveshaft bearing support to give a little room to manipulate the driveshaft.

10. Remove the input shaft locknut locking plate. It's basically a cup-shaped plate with a nut-shaped hole that is pressed into the flange. You can pull it out with needle-nosed pliers. Use a small screwdriver to bend the edges in if you can't get it out. The bentley manual calls for a new one, but I reused mine by restoring it to its original shape.


11. Mark the input shaft and nut with a centerpunch so you can get them back in exactly the same position. This will prevent you from overloading the bearings underneath. Next to this mark, mark the flange so you can see this position with the socket over the nut. Likewise, count the revolutions as you back of the nut (next step). Also mark the outside of the flange and the differential casing so you can put the flange back on in the same orientation.


11. Remove the input shaft lock nut with a 32mm (1-1/4") socket. This is going to take a lot of torque. I'm cheap and dirty, so I used the driveshaft bolts and a small prybar to hold the input flange in place. As a bonus, this setup olds the prybar and the socket in place. I had to use the impact wrench on this bad boy and had to turn it up to it's max setting (about 550 ft-lb). If you can find one, you should really use a proper impact socket, but given the size of this bad boy, I figured my chances of breaking it were very low. Plus I had a hard enough time finding a socket this size!
When I put the locknut back on, I marked the back of my socket with a marker to match the location of the mark on the lock nut. Then after the number of turns from step 11, you can line up this mark with the mark on the flange that you made on disassembly (you can just make out the black mark at the 3 o'clock position on the socket in this picture from assembly). I had to use the impact wrench again.


12. Pull the input flange off. Mine came off by hand, but you might have to use a couple of taps with the rubber mallet. Now you will (finally) have access to the culprit: the input shaft seal (brown).


13. Use a small seal puller to get the seal out. Have a rag ready, a couple ounces of fluid is waiting for you behind this seal. Sticking to my cheap and dirty tendencies, I pried mine out with a large screwdriver.


14. Put oil all over the new seal and, carefully, evenly, tap it into place with the flat side of a small ball peen hammer.

15. Ahhhh... easy for me to say: assembly is the reverse of disassembly.

Some good info here too: http://forum.e46fanatics.com/showthread.php?p=8703979
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Last edited by jcreme; Sun, Oct-12-2014 at 10:05:49 PM. Reason: Buy BMW Diff oil
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Old Wed, May-26-2010, 04:39:16 PM   #2
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Awesome! Thanks for the write up.
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Old Fri, Aug-13-2010, 08:35:51 PM   #3
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Update: DUH the diff didn't like the non-BMW fluid. It's noisy! Sounds like tire rubbing. Off to BMW to get the stuff with the friction reducer....
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Old Wed, Aug-18-2010, 08:36:20 PM   #4
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Quote:
Originally Posted by jcreme View Post
Update: DUH the diff didn't like the non-BMW fluid. It's noisy! Sounds like tire rubbing. Off to BMW to get the stuff with the friction reducer....
Great DIY!!

We have actually created a Rear Differential Service Kit to help aid in this project...

Click HERE for more information.


Please let us know if you have any questions! Feel free to shoot me a PM or email.

Best,
James
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Old Fri, Apr-22-2011, 12:49:37 PM   #5
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Default Re: Rear Differential input seal replacement

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Originally Posted by jcreme View Post

11. Mark the input shaft and nut with a centerpunch so you can get them back in exactly the same position. This will prevent you from overloading the bearings underneath. Next to this mark, mark the flange so you can see this position with the socket over the nut. Likewise, count the revolutions as you back of the nut (next step). Also mark the outside of the flange and the differential casing so you can put the flange back on in the same orientation.

/showthread.php?p=8703979"]http://forum.e46fanatics.com/showthread.php?p=8703979[/URL]
Does anyone have any recommendations if I forgot to match mark the input shaft to the nut during disassemble? I could potentially measure back lash with an indicator by pushing the input all the way in then pulling it out that small amount, but I don't have a spec. A torque spec may also get me close but I have not found one in my manual.
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Old Wed, Apr-27-2011, 02:58:06 AM   #6
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Sorry I don't have a link for you, but I'm certain that when I was researching for my job, I found a DIY on bimmerforums or e46fanatics and his assembly routine was not based on marking but based on torque alone. It requires a new crush sleeve.

And if I remember right, requires you to measure the torque required to turn the diff and rear wheels before disassembly (although, I bet an estimate is close enough).

Search bimmerforums or e46fanatics and see if you can find it.
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Old Mon, Nov-28-2011, 12:33:49 AM   #7
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Default Re: Rear Differential input seal replacement

Do you know if it's possible to replace the seal as describe on this DIY just using jack stands? According the pictures I could not identify how did you life the car.
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Old Mon, Nov-28-2011, 01:36:37 AM   #8
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Default Re: Rear Differential input seal replacement

Quote:
Originally Posted by jcreme View Post
Update: DUH the diff didn't like the non-BMW fluid. It's noisy! Sounds like tire rubbing. Off to BMW to get the stuff with the friction reducer....
Friction modifier

Quote:
Originally Posted by jcreme View Post
Sorry I don't have a link for you, but I'm certain that when I was researching for my job, I found a DIY on bimmerforums or e46fanatics and his assembly routine was not based on marking but based on torque alone. It requires a new crush sleeve.

And if I remember right, requires you to measure the torque required to turn the diff and rear wheels before disassembly (although, I bet an estimate is close enough).

Search bimmerforums or e46fanatics and see if you can find it.
Actually you need to remove the entire carrier assembly from the differential and measure this with the pinion alone. It is an inch pound value. If you turn the whole assembly - pinion, ring gear/carrier assembly, drive axles, halfshafts, hubs - you will be looking at a foot pound value. The inch pound value of rotating torque - also called preload - on the pinion is fairly insignificant and will likely measure out between 1-2 foot pounds. A proper range of values for the pinion preload is 12-23 inch pounds. And yes this does require a new crush sleeve.
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Old Mon, Dec-05-2011, 08:55:55 PM   #9
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Default Re: Rear Differential input seal replacement

Great DIY on this forum!
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Old Sun, Dec-11-2011, 01:07:31 PM   #10
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Do you know if it's possible to replace the seal as describe on this DIY just using jack stands? According the pictures I could not identify how did you life the car.
I used jack stands. Not at particularly space-demanding job.


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Discussing Rear Differential input seal replacement in the Faults, Fixes and DIY Forum - Please share your experience and knowledge with other members by contributing your own DIY, or by helping another member find the elusive fix! at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)