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Fixed my "rebuilt" differential

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    Fixed my "rebuilt" differential

    So I get this diff that is suppose to be rebuilt. I put it in and its had a major bearing whine. I've never rebuilt a diff but I am sure it wasn't suppose to whine this bad. I also noticed the flange was a little wobbly on the driver side. I put in the driver side outside bearing race till there is no movement with the flange and I measured the gap to make the shim. .0600" Seems kinda thin since the small shim BMW makes is 1.8mm. But as seen in my other thread, I made a shim and put it in. the whine reduced but I notice a lot of slamming.

    Later on a had to replace my guibo. And while I was down there I noticed a lot of backlash in the diff.

    Fast forward to trying to use medium case flanges and e30 axles in a small case lsd, when I removed the flanges to check the shaft seals (then realized that the flanges themselves were sticking out too far) I pulled out the carrier. I wanted make sure there wasn't any damage from the flanges hitting the spider gear pins. No damage as I didn't go far before I realized my car was spraying Amsoil diff lube everywhere.

    As I was reassembling everything, using the shims that came with it, I noticed the carrier wasn't tight between the outer races, and there was about .250" of backlash. Minchia! Earlier when I put the smaller shim in it tightened up the carrier but pushed it further away from the pinion. Using all the shims I could find between my two diffs and a couple spare shims, I re-set it up to .004" backlash and .0016" play between the carrier bearings (should be 0000 with 11 in/lbs of rotating resistance on new bearings.) But I needed my car today so I left it for now. Put back in the ti's stock axles after repacking the noisy cv joint (reason why I was trying to use e30 axles.)

    This morning, the car's rear end is quiet as a mouse. When I move into my new shop in November (with lights and heat), I will remove the ring gear, leave the driver side shims, tighten the 4 bolts down on the passenger side outside bearing (without shims) till I get 5 - 10 in/lbs of rolling resistance, measure the gap and make the shim.
    Last edited by b*saint; 10-09-2012, 06:22 AM.
    Ma che cazzo state dicendo? :|

    #2
    cool!

    I know my trans has a lot of backlash in it but the diff does also and I get a clunk in the rear when I depress the clutch at low speed while rolling. I am going to go through my diff as well to hopefully get rid of that low speed clunk.

    Where did you obtain your diff setup specs?

    Comment


      #3
      Online. Somebody had them for a medium case, but I figure the bearing is the same part number so it wouldn't hurt using those specs.
      Ma che cazzo state dicendo? :|

      Comment


        #4
        I know of no authoritative source for the differential specifications, but what I've culled from online references is:

        Backlash .06-.14mm (.0024-.0055in)
        Pinion Preload ~.20nm (21-28in-oz).
        The car makes it possible, but the driver makes it happen.
        Jim Levie, Huntsville, AL

        Comment


          #5
          Thats essentially the same info I have.

          Levie, does it sound like I missed anything that could be an issue in the future?
          Ma che cazzo state dicendo? :|

          Comment


            #6
            Originally posted by b*saint View Post
            Thats essentially the same info I have.

            Levie, does it sound like I missed anything that could be an issue in the future?
            I have a hard time visualizing exactly what you did and the process. Setting up a differential can be an iterative process that goes like:

            1) Set pinion preload
            2) Adjust output shaft shims for correct ring gear backlash (check at several points around the ring gear).
            3) Use prussian blue or similar to check pinion to ring gear mesh. The contact pattern should be in the middle of the ring gear. If towards either side of the ring gear the pinion shaft shims need adjustment and you cycle back to (1).
            The car makes it possible, but the driver makes it happen.
            Jim Levie, Huntsville, AL

            Comment


              #7
              I know it's an old post, but it's exactly what I need - jlevie where are the pinion shaft shims located? I know the output shaft ones are, but I haven't seen any shims on the pinion shaft when disassembling the diff. Except there was a pretty big spacer (cca 8mm) under the outer pinion shaft bearing race.

              I have the feeling I'm missing something ... =)

              Comment


                #8
                Wow what a bump!. Im pretty sure thats it. There might be thinner shims in a shim kit, but I've seen it where the biggest single shim passes spec so there's no shim stack.
                Ma che cazzo state dicendo? :|

                Comment


                  #9
                  So how would you adjust the depth of the pinion if there's no shims? This is what I don't understand =) Only with the crush sleeve? Wouldn't that affect break off torque?

                  Comment


                    #10
                    There used to be a shim kit you could buy from the dealer. Who knows if its still available. Dan at diffsonline may have a solution for you if you call them up.
                    Ma che cazzo state dicendo? :|

                    Comment


                      #11
                      Shim kits are still available. i got my part numbers from Realoem and you have a few places to choose from for purchase
                      1988 325 non-letter Seta "Bronzit"
                      1991 325ic "Laguna Green" (Sold)
                      1993 325i "Laguna Green/Silver" (Sold)
                      1998 528i "Artic Silver" m-sport(totalled by drunk driver)
                      2000 528i Titansilber/gray m-sport
                      2000 528i Titansilber/black m-sport(sold)
                      2001 525i Anthracite m-sport(sold)
                      2013 750i Black/Black m-sport "Beast"

                      Comment


                        #12
                        Shim kits from ecs:



                        There is no "pinion" shim kit - at least I haven't found it.
                        Does anyone know how to set the depth of the pinion on these diffs?

                        Comment


                          #13
                          Originally posted by crappycoco View Post
                          Shim kits from ecs:



                          There is no "pinion" shim kit - at least I haven't found it.
                          Does anyone know how to set the depth of the pinion on these diffs?
                          come on man!
                          just search 33129065179 thats one set right there
                          the numbers are on realoem, like i said
                          a ton of places sell the kits, including ECS
                          Last edited by wilholl; 11-15-2015, 05:53 PM.
                          1988 325 non-letter Seta "Bronzit"
                          1991 325ic "Laguna Green" (Sold)
                          1993 325i "Laguna Green/Silver" (Sold)
                          1998 528i "Artic Silver" m-sport(totalled by drunk driver)
                          2000 528i Titansilber/gray m-sport
                          2000 528i Titansilber/black m-sport(sold)
                          2001 525i Anthracite m-sport(sold)
                          2013 750i Black/Black m-sport "Beast"

                          Comment


                            #14
                            So the output shaft shims adjust the location of the ring gear side to side and also the backlash while at it. Then you adjust the pinion so that the contact patch is center on the ring gear (since it moves as the gears are tapered).

                            But why do you need shims for the pinion if there is a crush sleeve? Is it so if it is crushed too far, you can put in a shim and then re-crush it to get it where it needs to be?

                            Doesn't the position of the pinion affect the backlash as well (because the gears are tapered)?

                            Comment


                              #15
                              wilholl, great now I feel like a complete idiot =D
                              Somehow it slipped my mind and ecs doesn't categorize them as a 325is fit ... strange. Thanks for helping, very appreciated!

                              Makes much more sense now.

                              Andrew, from my limited understanding the crush sleeve only affects the preload and there is a shim in there from the factory (or at least mine had one in there already). The pinion shim should position the "mark" Up/down, while the axle shims position it left/right.

                              Originally posted by AndrewBird View Post
                              Doesn't the position of the pinion affect the backlash as well (because the gears are tapered)?
                              Hm, I think also the grooves are tapered, so in my head that means it shouldn't. Very interested if someone could explain this. Also, I'm intrigued why preload is so important for checking backlash?
                              Last edited by crappycoco; 11-16-2015, 12:33 AM.

                              Comment

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