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Thread: e34 diff swapping need-to-know

  1. #51
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    moroza is offline MORΩN ΛABIA BMW CCA Member
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    A stock E31 diff case needs to be drilled and tapped to properly bolt up to an E34's front diff mounting bracket. It has a completely different style of mounting and uses only the front two holes; the casting is the same, just missing a hole.

    I just got a 2.65 in the mail and am learning things.

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    That's good info, I well update the first post to include that. Thanks.

  3. #53
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    More info now that somebody referenced this thread.

    Quote Originally Posted by dgoodsy View Post
    2) Medium case diffs came in cars with 6 cylinder engines with the only exception being the m5 which came with a large case diff. Large case diffs came in cars with 8 or 12 cylinders with the only exception being 3.0 v8 cars which had the medium case diffs
    this is a handy chart to find the diff ratio that these cars had from the factory. http://www.vinesauto.com/diffratio.htm
    This is the case for US-market cars only. At least some German-market 535i had large-case diffs. We have a few members in other markets on here, and their info regarding what car had what fitted may vary. Ditto for Canadians (and now Americans) importing Japanese and other grey-market cars.

    The narrower diff requires longer axles which is why 525/530A/535A axles are a different part number than other e34 axles. Obviously the medium-large diff is a bit bigger, and happens to be the same size, width-wise between output flange mounting flanges, as the large case diff. This is why the medium-large diff cars share axles with large case diff cars (with the exception of the beefier 540 axles, see 4) below).
    The lengths of the axleshafts aren't the (only) issue; the boltpatterns are different. See here.

    US-market E34 axleshafts below. This list should be complete and most of it I've verified first-hand.
    33211226720 - all 525i, 530iA, >1/91 535iA. Smaller boltpattern.
    33211226622 - 530iM, 540iA, <1/91 535iA, 535iM, M5. Larger boltpattern, 30.5mm thick at the joints, 27mm thick in the middle.
    33201229245 - 540iM only. Identical to the 622 except 30mm thick in the middle (does not affect fitment in any way, and takes the same boot repair kit).

    The input flanges also vary between diffs, however not the same way the output flanges differ. According to realoem the input flanges for the m20 525s, both manual and auto are the same as all 535 input flanges, as well as the input flanges for the auto m50 525. (After further research, according to realoem, auto 530s had this input flange for production months later than 9/93 and m50 manuals with a production date up to and including 8/90)(80mm BC, M8 bolts). The input flanges for the manual m50 525s (after 8/90)are the same as the input flanges for all manual 530s as well as the autos with production months up to and including 9/93 (86mm BC, M10 bolts). **This information is based only on the bolt size and pattern for the drive shaft cv joints on realoem, (there is no information on the input flanges themselves on realoem) and should be taken with a grain of salt. I believe medium case input flanges are also interchangeable between diffs.
    Yes, take it with a grain of salt. It's confusing and tedious to verify, and I'm not going to do it exhaustively for every E34. Recommend verifying on a case-by-case basis before buying any parts. RealOEM's interchange pages are NOT always correct; see here for example, listing the smaller 720 axleshaft as fitting a 535iM, but when you click on the link that PN is (correctly) nowhere to be found.

    Apparently M50 525i sedans all had 86mm 25-spline driveshaft CV 26111229075 regardless of transmission, but 525i wagons (all M50, and in the US all auto) had 80mm 24-spline CV 26111226881.

    6) The large case diffs will bolt in to a medium case diff car (half shafts may need to be swapped as well if the car had a medium regular diff previous).
    Except an M20 or M50 sedan. See below. Also, hub flanges will need to be swapped if the car was a "medium regular" with the smaller 720 axles.

    8) some people say it is a relatively simple task of swapping input flanges, others won't do it for fear of changing pinion depth, and ruining pinion and ring gears. Typically the ones who say it is a pretty simple task are the ones who have done it, those who say it isn't easy haven't done.

    My experience with a brand-new large-case crush sleeve is that it took well over 200ft-lb to crush it. Compared to the 137ft-lb torque spec on the pinion nut, that's a big margin of error, but then I've seen bigger hamfists. Do not use an impact gun to torque it.

    UPDATE: done a couple more of these and can report that while it takes a lot of torque to crush a brand new sleeve, this torque diminishes greatly once it's close to its final point. Overtorquing is easy to do, so be careful.

    1) Will the diff housings for the large case diffs bolt up without modification (other than maybe a chassis specific diff cover) where a medium case diff was? (and vice versa, provided the existing axles are compatible) see 'fact' 6)

    Yes. Diff covers are specific to medium- and large-cases, but front/side and rear brackets are common, and E34 and E32 subframes all have the same geometry for diff fitment purposes. Euro 518, 525tds, and some others have a different subframe and diff mount, where the diff bolts directly to the subframe with 4 bolts and no brackets or bushings. All the ones I've seen also have 4-bolt U-joint yokes at the driveshaft. It's possible some early US 525i have this setup as well.

    2) Do the e31 diffs work in the e34? I have read that they bolt into the e32 with the e32 diff cover, which would mean that they should bolt into the e34 with the appropriate diff cover, does it not? The e31 diff CAN work, see post 51 of this thread.

    See here for some details.

    3) According to realoem the drive flange (the part that the outboard end of the half shaft bolts to) for the 525 is different than the drive flange for all other e34 cars, but realoem gives no information on bolt size and pattern for it. I have heard of some who swapped in new half shafts to match their new diff with different output flanges (in an e30 if I remember correctly) and found that the outboard end of the half shaft did not match the drive flange, but can’t find where I read that now. Can anyone confirm or deny this is that the case with the non 525 half shafts mating with 525 drive flanges?
    This would only be a problem when swapping a large case diff into the 525 because there are no output flanges that work with the large case diff AND the 525 half shafts, meaning non 525 half shafts need to be used.
    An interesting note here is that my 525 (a touring model imported from japan) according to realoem uses the same drive flanges as the US market 530, 535, 540 and m5 cars, but the same axles as the US market 525 (which would lead me to believe that if 525 axles work with ‘non 525’ drive flanges as on my car then non 525 axles should work with 525 drive flanges). Then curiosity drove me to check realoem for the US market 525 touring, and apparently it too has the same drive flanges as the 530, 535 540 and m5 cars. Upon further digging realoem revealed that my car and the US market 525 touring use the same input and output flanges as other m50 cars.
    This is still outstanding, anyone have anything solid?

    525i sedans (M20 and M50) used 74mm wheelbearings that only have one possible hub flange, for the smaller 720 axles (see above).

    525i wagons used 80mm wheelbearings like all other E34 and E32, for which there were two options for inner hub flanges: smaller for the 720 axles, and bigger for the 622. Both use the same outer hub, wheelbearing, and trailing arm, all of which are different from 525i sedans'.

    Medium-case diffs could have either 720 or 622 axles depending on (easily-swapped) diff output flanges, corresponding with (not as easily-swapped) hub inner flanges, but large-case diffs only use the larger 622 axles, which require the bigger hub flanges and the rest of the hardware. Bottom line: to fit a big-case diff on a 525i sedan, you need trailing arm assemblies from a 525i wagon or any other (US-market) E34 or E32*.

    *E32 outer hubs have a ~7mm higher offset and take specific brake rotors.
    5) Is the input flange swap as simple as remove and replace with an impact gun (of course with compatible input flanges)? It seems to me some have said that there are specific skills and tools for this job, or am I getting confused with swapping internals? see 'fact' 8)

    No. Removing with an impact gun is ok, but do NOT use one to put it back on. Use a torque wrench to carefully tighten to 137ft-lb (per Bentley, apparently for all diffs large and medium). You're supposed to use a new lockplate as well (I reuse them at discretion). Otherwise, yes, easy swap.
    Last edited by moroza; 03-30-2020 at 03:26 AM.

  4. #54
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    Thanks a lot Moroza, I have updated the first post with your information. Lots of information here.

  5. #55
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    moroza is offline MORΩN ΛABIA BMW CCA Member
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    Does anyone (paging Wanganstyle ...) know if the large diffs have an offset difference like the mediums? Will a 2.65 gearset fit a 4.something LSD carrier, and if not, what's the cutoff?

  6. #56
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    I remember looking for this same information and I seem to think that all 210 lsd sections had the same offset, but can't find that anywhere now.

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    Quote Originally Posted by moroza View Post
    Does anyone (paging Wanganstyle ...) know if the large diffs have an offset difference like the mediums? Will a 2.65 gearset fit a 4.something LSD carrier, and if not, what's the cutoff?
    No 210mm diff came from the factory with a final 4 or higher; 4,10 is a Bmw Motorsports only product and it’s popular for those with deep pockets for the gear ($970) and the work to install.

    2.65 is in the manual v12 cars; it’s stupid honestly to use unless you have a manual v12 car.

    210mm units share gears, so you can bolt a 2.82 to a unit that originally came from the factory with a 3,91. Why one would do that I don’t know.

    If looking for ultra low rpm for commuting Honda made a car called the insight. It has a 5 speed manual with double overdrive (3 is 1:1, 4-5 are both overdrive) and an electric assist motor; it’s also 0.25 cd which no Bmw has. Much better choice to save fuel than stuffing a 2.65 into a car and making it a slug.

    A Honda Insight costs less than installing some slug low gear to make a Bmw slower; it’s also 61/69mpg epa.
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  8. #58
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    Shrug. I had a 2.65 in my 544 and liked it. "Slug" did not come to mind when driving it. Just wondering if an S3.15 carrier could accept those gears.

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    e34 diff swapping need-to-know

    Quote Originally Posted by moroza View Post
    Shrug. I had a 2.65 in my 544 and liked it. "Slug" did not come to mind when driving it. Just wondering if an S3.15 carrier could accept those gears.
    Slug compared to the Bmw nazi engineers intended use of a 2.65 with 6mt + v12.

    12 > better than 8;

    My stock e38 5400cc with its 5eat /2.82 was faster than a s62b50 car from 85-115mph but then was dropped behind quickly when the Itb-8 came into the top end.

    The 544 with a 3.15 is good but nothing close to the v12. 2.82 isn’t bad either. 2.65 would be pretty sluggish especially with lack of vanos.
    Last edited by wanganstyle; 11-19-2018 at 12:52 AM.
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  10. #60
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    Wanganstyle, are you aware of there are 2 different offset LSD center sections for the 210mm diff? I'm trying to read between the lines in your recent posts here and am not feeling confident. My purpose of this thread is to share facts and remove ambiguity from information..

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    e34 diff swapping need-to-know

    Quote Originally Posted by dgoodsy View Post
    Wanganstyle, are you aware of there are 2 different offset LSD center sections for the 210mm diff? I'm trying to read between the lines in your recent posts here and am not feeling confident. My purpose of this thread is to share facts and remove ambiguity from information..

    Sent from my SM-G930W8 using Tapatalk
    Why do you need spoon feeding?

    Spoon feeding requests are common; some
    Simple search would find another spoon feeding thread

    210mm diff questions for E36 fitment - when is a 210 not a 210?
    https://r.tapatalk.com/shareLink?sha...5&share_type=t

    There are 3 different generations of lsd capsule for the 210mm diff

    Also two different clearance holes size 12.5mm and 14.5mm

    All of them would have different part numbers and will somewhat interchange if have the correct bolts or spacers or the ability to bore up in size

    So there would technically probably be 4-5 different part numbers that interchange.


    If you want a technical drawing with numbers quaife has it posted. Wavetrac and other aftermarket brand new lsd manufactures also have compatibility charts on websites

    I guess the E34 crowd is just against paying for new parts and looking for simple compatibility data from simple places.
    Last edited by wanganstyle; 11-25-2018 at 02:28 PM.
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  12. #62
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    Does anyone know what the outboard drive flange diameter is?
    I'm doing a transplant from a totaled e34 540, motor, trans, drive shaft and diff to a 94 e34 530.
    I've already transplanted the prestine interior from the 540 to the trashed interior of the 540, steering column was also swapped.
    I screwed up and let the totalled chassis go not realizing that the half shafts and outboard drive flanges were different.
    I realized my error when I tried to mount the half shafts from the 530 to the e34 540 diff and they wouldn't fit, the 540 diff has larger diameter flanges.

    Now I have to order replacement half shafts and I have a guy that has two drive flanges but before I purchase them I need to know if they are the correct diameter.

    Anyone who has information on the diameter please contact me: rtswapp@comcast.net

    Wife is going to execute me if I don't get this car up and running soon and get it out of the garage.

    Thanks

    Ron

  13. #63
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    e34 diff swapping need-to-know

    Quote Originally Posted by rswapp View Post
    Does anyone know what the outboard drive flange diameter is?
    I'm doing a transplant from a totaled e34 540, motor, trans, drive shaft and diff to a 94 e34 530.
    I've already transplanted the prestine interior from the 540 to the trashed interior of the 540, steering column was also swapped.
    I screwed up and let the totalled chassis go not realizing that the half shafts and outboard drive flanges were different.
    I realized my error when I tried to mount the half shafts from the 530 to the e34 540 diff and they wouldn't fit, the 540 diff has larger diameter flanges.

    Now I have to order replacement half shafts and I have a guy that has two drive flanges but before I purchase them I need to know if they are the correct diameter.

    Anyone who has information on the diameter please contact me: rtswapp@comcast.net

    Wife is going to execute me if I don't get this car up and running soon and get it out of the garage.

    Thanks

    Ron
    Do you own a:
    Tape measure? Ruler, or vernier caliper?

    .........




    Realoem + the vin number of your 530 and ex donor 540 will tell you. Or just choose any E34 540
    Last edited by wanganstyle; 03-03-2019 at 12:54 PM.
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  14. #64
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    moroza is offline MORΩN ΛABIA BMW CCA Member
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    I don't know the diameters offhand (EDIT: flanges are slightly bigger than CV joint housings, which on the large axles are 108mm OD), but I can show you that the two have visibly different castings. Large-diameter on the left, small on the right:
    Picture 229.jpg
    Last edited by moroza; 03-06-2019 at 06:05 AM.

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