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Thread: STR Z4 Coupe "build"

  1. #76
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    Quote Originally Posted by z3papa View Post
    Murph -- what did you start with and what did you finish with.
    ok, finally dug up my info...

    Started at 30/90 ramps with 40% lockup.

    Pretty sure it changed when I had it rebuilt to 3.07, I think it went to 40/60, but neither Jim nor I wrote it down, whoops.

    in 2011 the power-on push was gone, but I couldn't get any off-throttle rotation.

    I think I'm going to move to 40/90 that Jim has available this year.

  2. #77
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    Quote Originally Posted by Toby Larsson View Post
    The OS Giken lsd for the new Camaro is out and is being used successfully in both drifting and roadrace. The Ford unit has been tested for awhile and should be available very soon. The Ford unit opens up some interesting options with large number of cheap gear ratios available that can be mounted in the aluminum housing from the Cobra and equipped with cv's can be mounted in most BMW subframes as a IRS setup. Let me know if you're interested in one and I can put you in touch with the right person for more info.
    Well I'll be damned... thanks Toby! OS Giken told me not 3 months ago they were NOT going to make a diff for the Ford 8.8". Please PM me the contact - thanks!!!



    And yes, the 8.8" aluminum IRS housing has been put into BMWs before, like the E36 LS1 swap from one of our former customers. We've got our eye on another chassis that needs this IRS diff swap, too. The ring gear is SO strong, yet the aluminum housing is lighter than the cast steel BMW units. It also does not carry the BMW tax - there are dozens of gear ratios available for $180/set. If we can get an OS Giken for it now... that's great news.
    Last edited by Fair; 01-27-2012 at 03:51 PM.
    Terry Fair @ Vorshlag Motorsports

  3. #78
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    Ho-hum, getting antsy about the shocks. Going to poop self when I try the adjusters for the first time. By comparison,

    Bilstein Clubsport



    AST 4150




    Time to get off my lazy bum and get in the shop. I have a ring gear to clean and some spacers to fab for a work project.

  4. #79
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    Quote Originally Posted by Fair View Post
    They make a damn fine diff - I love the one in our E46 330. Dan @ Diffsonline is the source. About $1700, which is painful. Not a big deal - see you chose the WaveTrac.
    We have a BMW racing LSD. I looked into getting an OS Giken but with needing to get the dampers rebuilt, re-gearing from a 3.46 to a 3.23 and fixing everything else with the car there is no budget.

    Is $1700 complete from Dan or is that just the LSD unit? If that's set up, that's a great price. I can get the diff alone much, much much cheaper than that, but then it needs bearings, setup etc and the E46 diffs are not easy to set up as I'm learning now trying to do it myself.

  5. #80
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    It's DONE!



    Making ring gear steak mmmmm (PS I have the best wife in the world )



    Gettin ready for bolts



    Races much easier to install when warm (~150-200F). The right side slid right on!



    There was a guy on e90post that had to cut his case for the Quaife to fit... But the recesses in the case are a perfect fit when you put it in this way. No case modification required for the Wavetrac.



    Bearings and snaprings installed, almost there! It took a lot of finesse to get the second snapring in. If you are doing this make absolutely sure the snaprings are FULLY seated into the groove.



    Checking backlash. The stock open diff was at .003", this one is right on the tight edge of spec at .0025". Which is a good thing becuase I have no idea where I would source the different size snaprings...



    Drive side pattern



    Coast side pattern



    Getting the last of the old oil out



    Oil seal installation SST which is a repurposed subframe bushing removal SST



    Always, ALWAYS use a new axle circlip! (new on top)

    Last edited by illinipo; 10-18-2012 at 11:14 PM.

  6. #81
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    nice pete! damnit between you posting that and the rolex 24 I'm gonna go try and be productive. wish me luck.

  7. #82
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    Nice work.

    You can't buy the snap rings, which function as the preload and backlash shims. I bought a few junked diffs to build up a collection of them.

    You don't show pictures of it but I hope you checked the preload of the diff. You need to set that correctly before you put the pinion in, and before you check the backlash.

  8. #83
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    Do you mean the side bearing preload? Insert sheepish look here. Couple thoughts on that to justify having forgot it. The preload is much more critical for taper roller bearings than this type, which basically just needs enough to keep the balls rolling. Since the backlash is so close to what it was stock I imagine the preload is also within a couple thou. All of the balls are rolling (so it is not too loose) and the resistance to spin the diff feels about like it did before (so it is not too tight). Besides, not sure how I would measure preload without having a thinner snapring on hand...

    Ah well, if the bearings fail they fail and it will have to come back out. I'm confident that this will work. You'd be amazed how many shops toss together transaxles with LSD's without bothering to check preload!

    I did not remove the pinion.

  9. #84
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    I don't know the spec for the non-tapered bearing diffs, but would think there is one. Your diff looks a lot like my E46 diffs with the exception of the bearings. But yes, you need to set the preload on the carrier when you change the bearings or the LSD unit. Your bearings might not be exactly in the same location as they were on the factory open diff and there are production tolerances on the bearings as well as the LSD unit.

    You can't check it with the pinion in because the pinion bearing has preload as well, and the gear mesh adds friction. If you mark the location of the pinion nut you can remove it and press out the pinion then put it back without screwing up the pinion depth.

    You're correct that you would need thicker (if the preload is too low) or thinner (if the preload is too high) shims to correct it. The total shim thickness sets the preload, and the relative thickness of the two shims sets the backlash. Thinner shims are easy - you lap the shims you have to get them to the right thickness. Thicker shims you need to source from a junked diff. I have a bunch.

    If I were you I'd call Dan at Diffsonline and ask him what the spec is for the Z4 diff. Then pull it and check it. You don't want to have a failure at an event or worse, on the road driving to an event. Shops do all sorts of incorrect things. You seem like a guy that does things properly.

  10. #85
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    For your next build, wrap the ring gear in tinfoil before you heat it up so you don't stink up your whole house

    I've done >20 diffs, your work looks good !

  11. #86
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    Thank you very much, Toby, it is nice to hear that from an experienced BMW guy.

    I had been cleaning the gear for nearly an hour before that, so fortunately the smell didn't get past the exhaust fan over the oven

  12. #87
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    Quote Originally Posted by John V View Post
    We have a BMW racing LSD. I looked into getting an OS Giken but with needing to get the dampers rebuilt, re-gearing from a 3.46 to a 3.23 and fixing everything else with the car there is no budget.

    Is $1700 complete from Dan or is that just the LSD unit? If that's set up, that's a great price. I can get the diff alone much, much much cheaper than that, but then it needs bearings, setup etc and the E46 diffs are not easy to set up as I'm learning now trying to do it myself.
    When Vic/Tunnell had your car they had two diffs, did you only get the one in the car? I remember they spent a lot of money at the time to build those two diffs, what is it you don't like about them/it?

    Here's the company in CA that builds alot of the OSG's for Viper and Corvette's, they have also done a number of BMW's and they did a TT Supra for me when I was in a hurry getting it done.


    Talk to Devin, http://gounitrax.com/


    Vac motorsports are now an OSG dealer as well.
    Last edited by Toby Larsson; 01-28-2012 at 10:44 PM.

  13. #88
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    Has anyone made custom spherical RSM's with mcmaster 2995K33 or similar? I can definitely do that for less than $160, even if I have to make the flanges. But I would like to try to use the stock RSM plate to start off.

    The alternative is pay $16.42 to ship the $15 rogue RSM "track" bushings and forget about it.

  14. #89
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    hmm never thought of that but a good thought. LMK if you want something as I have an account at mcmaster

  15. #90
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    Quote Originally Posted by Toby Larsson View Post
    When Vic/Tunnell had your car they had two diffs, did you only get the one in the car? I remember they spent a lot of money at the time to build those two diffs, what is it you don't like about them/it?
    Two rear ends came with the car - one with the LSD and the other with a spool.

    The only thing I'm changing is the gearing - from a 3.38 to a 3.23. I haven't driven the car enough to know whether I like or dislike the diff but I did want to price the Giken as the people who have it seem to love it.

  16. #91
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    Well that RSM talk is moot as I just picked up a set of Ground Control sphericals for 60 bucks Might have to fab a couple spacers since they will come with 12mm and I believe the AST are a 10mm shaft. No big deal.

    Next order of business, maybe a moderator could move this thread to the build thread subforum? It's nice to get all the views here but it makes more sense to be in there.

  17. #92
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    Get pumped - wassup61 is coming this weekend to make a serious dent in the reassembly.

    Meanwhile I have to find time this week to drill out the exhaust stud that broke off in one of the flanges... I have a feeling that will turn into a 6 hour job real quick.

  18. #93
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    Did you ever figure out what the preload spec for your diff is?

  19. #94
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    Just googled it. Page 8 of the metric mechanic pdf has info on the M variable diff, which has the same snapring and ball bearing design.

    We’ve developed a method for expanding the case
    so these bearing can be shimmed and pre-loaded to
    the proper 9 to 11 inch pounds of rolling torque
    and still be able to set the back-lash on the ring and
    pinion to .0030” - .0035”.
    http://www.metricmechanic.com/pdfs/m...al-booklet.pdf


    At first, I was thinking to check it like I have done in the past with transaxles, by putting a smaller snapring in and using a feeler gauge to determine the extra space. However, it looks like BMW checks preload by the friction of the bearings, like I said in my earlier post.

    Quote Originally Posted by illinipo View Post
    All of the balls are rolling (so it is not too loose) and the resistance to spin the diff feels about like it did before (so it is not too tight).
    That is a whole new concept to me to actually use this torque to measure preload. Seems to me there are a couple other variables that can change this torque value and goof up your reading... but that is why I don't work for BMW.

    But, like you said,

    Quote Originally Posted by John V View Post
    You can't check it with the pinion in because the pinion bearing has preload as well, and the gear mesh adds friction.
    And only now do I understand why that matters. If you measure the preload by friction, you can't have the gear meshing friction in there too.


    It all adds up to a massive pain in the neck, and the car owner agreed with me that we will drive it like it is and check the bearings and gear after a couple hundred miles when we change the fluid out.
    Last edited by illinipo; 01-31-2012 at 02:40 PM.

  20. #95
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    Having disassembled four E46 diffs now I cannot advise against that strongly enough. A couple of hundred miles is enough to destroy your bearings and potentially your diff if something lets go and gets into the unit.

    It's your stuff and you're free to do what you want - but it's not that much work to check it now.

    As for having other variables affect the reading... there isn't much. In the E36 TIS they list adjustment factors to add if you measure the rolling torque with the output shaft seals installed. Other than that and the difference between new / old bearings I can't think of anything. Assuming you have a good dial torque wrench.
    Last edited by John V; 01-31-2012 at 06:32 PM.

  21. #96
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    The number one diff killer is too much preload on the pinion bearing.

    If you see the speedo start acting funky, stop!

    That means that powdered bits of steel have stuck to the speedo magnet, and that is not good.

    I have had the best luck in setting the pinion preload like a bicycle wheel. I tighten the nut about 1/4 turn after there is no play in the pinion (after crushing the sleeve), and then resist all temptations to tighten it further.

    Diffs are very much a "feel" thing when setting them up.
    Last edited by Hellabad; 01-31-2012 at 07:31 PM.
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    1992 e36 325 track car

  22. #97
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    Quote Originally Posted by John V View Post
    but it's not that much work to check it now.
    Really? New axle seals, new pinion crush sleeve, and possibly new shims there as well. Plus resetting pinion preload and depth. And sourcing the right circlips, if I even need them. It's at least another full day in the shop and around $100, just to check the rolling torque of the diff.

    "marking the pinion nut and going back there on reassembly" is just another corner to cut. If I am going to the trouble of removing the pinion to check preload then it would be a new crush sleeve, then going in and re-setting depth and backlash. Avoiding this trouble was the point behind not removing the pinion in the first place.


    Let's examine failure modes.

    1. If the preload is too loose, the balls would not spin. You'd end up with flat spots on the balls eventually and the diff/gears would start to vibrate/moan/groan as the balls are worn down and no longer fit the races, and the ring and pinion start to tear each other apart. The sound would be plenty obvious and we would stop driving the car immediately and tear it down. This failure mode is moot because I have visually confirmed that the balls are, in fact, rolling quite excellently on both sides. So failure mode 1 will not happen.

    2. The preload is too tight. In this case the balls will start heating up like crazy and wear a loading pattern into the races, chipping little flakes of metal off. Symptoms would be difficult or impossible to install the second snapring (it took some convincing; did not slide in nor did it have to be hammered very hard), difficulty to spin the diff by hand and quick to lose inertia (it was not any harder to turn than stock and maintains inertia like stock), and groaning noise while driving, which would also cause us to stop driving the car immediately and tear it down.

    3. No failure. I'm willing to wager that the Wavetrac is built to .0005 tolerance, which is industry standard as of about 10 years ago. Meaning BMW also built it to .0005 tolerance. Which means the most the preload will be off from what it was stock is .001.


    The majority of tolerances taken up by the shims is in the cast case. Casting is WAY less precise than machining. Bearings these days are built to .0001 and sometimes .00005 for the super fancy expensive ones. And like I said before, the diffs are likely machined to .0005.


    Allow me to quote from our rules sticky. Let's

    * Agree to Disagree ...
    Quote Originally Posted by Hellabad View Post
    The number one diff killer is too much preload on the pinion bearing.

    If you see the speedo start acting funky, stop!

    That means that powdered bits of steel have stuck to the speedo magnet, and that is not good.

    I have had the best luck in setting the pinion preload like a bicycle wheel. I tighten the nut about 1/4 turn after there is no play in the pinion (after crushing the sleeve), and then resist all temptations to tighten it further.

    Diffs are very much a "feel" thing when setting them up.
    Agree, but I have not touched the pinion shaft on this install.

    And there are no electrical connectors on the diff... ?
    Last edited by illinipo; 01-31-2012 at 07:40 PM. Reason: Automerged Doublepost

  23. #98
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    Quote Originally Posted by illinipo View Post
    Really? New axle seals, new pinion crush sleeve, and possibly new shims there as well. Plus resetting pinion preload and depth. And sourcing the right circlips, if I even need them. It's at least another full day in the shop and around $100, just to check the rolling torque of the diff.

    "marking the pinion nut and going back there on reassembly" is just another corner to cut. If I am going to the trouble of removing the pinion to check preload then it would be a new crush sleeve, then going in and re-setting depth and backlash. Avoiding this trouble was the point behind not removing the pinion in the first place.


    Let's examine failure modes.

    1. If the preload is too loose, the balls would not spin. You'd end up with flat spots on the balls eventually and the diff/gears would start to vibrate/moan/groan as the balls are worn down and no longer fit the races, and the ring and pinion start to tear each other apart. The sound would be plenty obvious and we would stop driving the car immediately and tear it down. This failure mode is moot because I have visually confirmed that the balls are, in fact, rolling quite excellently on both sides. So failure mode 1 will not happen.

    2. The preload is too tight. In this case the balls will start heating up like crazy and wear a loading pattern into the races, chipping little flakes of metal off. Symptoms would be difficult or impossible to install the second snapring (it took some convincing; did not slide in nor did it have to be hammered very hard), difficulty to spin the diff by hand and quick to lose inertia (it was not any harder to turn than stock and maintains inertia like stock), and groaning noise while driving, which would also cause us to stop driving the car immediately and tear it down.

    3. No failure. I'm willing to wager that the Wavetrac is built to .0005 tolerance, which is industry standard as of about 10 years ago. Meaning BMW also built it to .0005 tolerance. Which means the most the preload will be off from what it was stock is .001.


    The majority of tolerances taken up by the shims is in the cast case. Casting is WAY less precise than machining. Bearings these days are built to .0001 and sometimes .00005 for the super fancy expensive ones. And like I said before, the diffs are likely machined to .0005.


    Allow me to quote from our rules sticky. Let's





    Agree, but I have not touched the pinion shaft on this install.
    OK. Resist the temptation that I have to resist. If you decide to change the front seal or whatever, mark the pinion shaft and nut, and retorque to the exact same spot. Crushing a new crush sleeve is not as easy as it sounds in the books, so I personally try to avoid it if I can.


    Quote Originally Posted by illinipo View Post

    And there are no electrical connectors on the diff... ?
    IIRc your car has it on the diff cover for the speedo? My e46 and e36 do.
    Last edited by Hellabad; 01-31-2012 at 07:59 PM.
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  24. #99
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    Quote Originally Posted by Hellabad View Post
    OK. Resist the temptation that I have to resist. If you decide to change the front seal or whatever, mark the pinion shaft and nut, and retorque to the exact same spot. Crushing a new crush sleeve is not as easy as it sounds in the books, so I personally try to avoid it if I can.
    Not sure I understand what you are trying to say here?


    Quote Originally Posted by Hellabad View Post
    IIRc your car has it on the diff cover for the speedo? My e46 and e36 do.
    Nothing of the like.

    Last edited by illinipo; 10-18-2012 at 11:16 PM.

  25. #100
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    What Jay said. You don't need a new crush sleeve. Mark it and reinstall where it was. If you understand the function of the crush sleeve you'll understand that this will maintain the exact pinion preload you have now.

    Yes, you'll need new seals. That's a small price to pay compared to destroying a diff.

    I'm not sure what you mean by "tolerance." I have four E46 diffs disassembled here. The difference between the thickest and thinnest pairs of shims installed in them is more than 2.5mm. That should tell you something.

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