Diff seal replacement

Discussion in 'E36 M3 (1991-1999) and E30 M3 (1986-1990)' started by surestart, Feb 13, 2020 at 6:59 PM.

  1. 13 Feb 2020 at 6:59 PM #1

    surestart Achieved official socks

    Mar 8, 2007
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    2000 e36 M3 convertible
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    Thinking of replacing the diff seal on my e36 M3. Does anyone know if I can just unbolt the prop from the diff and then change the seal or do I need to remove other items like the exhaust to get at it ?

  2. 13 Feb 2020 at 7:17 PM #2

    M3POWERBOY Sponsor

    Aug 25, 2011
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    Exhaust and prop needs dropping mate
  3. 13 Feb 2020 at 8:01 PM #3

    harrypevo Achieved official socks

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    Yeah, you're going to have to drop the exhaust to get all the shields out to get to the prop.
  4. 13 Feb 2020 at 9:30 PM #4

    tony66 Achieved official socks

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    i just fitted my standard rear exhaust [was a magnex on it] make sure you get a new set gaskets/seals at minimum for where it joins the cat section
    also budget time to work the 4 hanger nuts loose as they can be solid-good time to replace the rubbers too as when you drop the back box you normally find they are shot to bits
    ohh-and eat your breakfast-rear box is heavy,typical m3 of any era
    Aglanm3 likes this.
  5. 15 Feb 2020 at 7:08 PM #5

    Aglanm3 On the path

    Oct 22, 2018
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    Are you sure that the seals need replacement?! If there is a leak you should know the source first, is it the differential seals or from the differential filling or draining plug ( or anything else like rear gasket or speed sensor etc..)
    Then the differential has 3 seals one front seal and 2 side seals. You have to decide which one or all need replacement.
    The front seal will need the whole differential to be dropped. While the other 2 seals won't need dropping the differential.
    Dropping the differential isn't an easy job. If you have an extra help would be much easier. If not you should try to left an old M3 differential to know how heavy ( I mean it) it is.
    Do you have access to a lift/ garage or are to you going to do it in your driveway?
    If you are going to replace only the 2 side seals. In your driveway, this job might be straight forward or could be a nightmare.
    I've done this job recently and I can tell you, you might start making a list of many items to be replaced as well.
    1. Jack the rear of the car. Support the car. Be safe.

    2. Remove the rear wheels.

    3. Start by loosening the bolts and nuts between the exhaust and cat. These might be corroded and might need heat or angle grinder to cut them if badly corroded.( Will need replacement either way)
    One of my exhaust flanges snapped and I had to get replacement for it.

    4. Loosen rear exhaust brackets. Again the rear brackets and rubber supports might be badly corroded and rusty. The chances that they will need replacement is very high. You might need full set. Not cheap for M3.

    5.if succeeded to drop the exhaust then it's time to inspect the heat shield. Might also need replacement if in bad shape.

    6. Now it's the time to loosen the bolts that holds the shafts to the differential. 8 in each side as far as I remember. E12 socket. Make sure that you don't strip them otherwise it will be a nightmare. Make sure you have decent E12 socket and have proper grip on them. You'll need to apply the parking brakes to loosen them one by one. ( It's the time to replace them as well).

    7. You might need to drop the rear anti roll bar as well.

    8. Once you have everything away and down from your differential. It might be the time drain the differential oil. And replace it. That the best time to do it while you are there.

    9.Pry the differential output flanges with a big screw driver( dust covers might need replacement)

    10. Remove the bolts that hold the differential side covers then pry it with big flat screw driver. Make sure you mark the orientation ( top and bottom)each side will have shim make sure that you mark them and don't swap them. This is very important.

    11. Now you have these covers with the seals out. It's easy to press old seals out and get the new seals in. Make sure you mark the position of the old seals and fit the new seals at same position and depth.

    12. Replace the old C lock metal rings with new rings.

    13. Refit the differential side cover. Make sure you have them properly oriented. Mark the top and bottom.

    Then fit everything in reverse order.

    Follow torque specs for e36 M3.

    Be patient. Use lots of penetrating oil/wd40 or any other alternative.

    I might have skipped some details. But you have the major steps.

    I'd inspect the car first and start making a list of the items to be replaced.

    Good luck.
    Last edited: Feb 15, 2020 at 7:19 PM
    tony66 likes this.

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