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First update captured in blue font
I know this has been covered pretty well in lots of threads but all the threads I have found seem to have facts that contradict the next thread, or are ambiguous which leads to lots of confusion. So I am hoping to get it straight once and for all, and have all (or a lot) of the information in one thread. I searched through many threads to put this information together which was a pain, and I still have questions. Hopefully this thread will cut down on people posting new threads asking questions for which the search function seems to yield inconsistent and contradictory results.
My reason for getting into this is I have purchased a donor car for my manual transmission swap that is coming up, hopefully around Christmas. I was planning on swapping the diff from the transmission donor car to my car. The problem is that the donor car is a 3 series, so the diff will not swap into my car. ( I know I should have got a 5 series donor car but this 3 series was real cheap and I can probably part it out easier than a 5 series) I have a 525 auto which has a 4.10 diff, which will be far too short with the manual tranny (just shy of 3500 rpm at 62mph, .72 ratio top gear in the auto vs. 1.0 top gear in the manual) as well as the whole driveshaft/input flange issue (as described below, 'fact' 3). Also I would rather not swap the guts from one carrier to the other, I hear if you don't do it just right you will burn through the diff and be replacing it in short order.
My plan is for a turbo system in the future and this is not a tracked car so I don't care to have low gears. In fact the 3.23 is probably the lowest ratio I would want, 3.07 or 2.93 (maybe even 2.83) would be ideal since my goal for this car is primarily for cruising comfort a daily drivability and then performance after that.
Below is a list of the facts (I use the word fact loosely, I don't mean it isn't disputed anywhere. I have typed up what seems to be the most common 'opinion' I have found in other threads, and what seems to make most sense to me as well as realoem verification) that I have found while searching for information for my own swap and below that is a list of questions I have regarding diff swaps in the e34 cars. For the most part this should all apply to the e32 cars as well. Hopefully with your input we can move the questions into the facts section. Again my intent here is to clear up the 'facts' about diff swapping; I do not claim to be 100% right and please correct me where you know I am wrong. Please don't correct me on points if you haven't already put a decent amount of research into or have hands on experience with.
These “facts” I have compiled are for North American market cars. I know there are variances for Japan market cars from first hand experience and have read and assume there are variances for all other markets as well.
Remember Realoem can be your friend here, there is information there about bolt sizes and patterns for input and output flanges, you can also cross reference part numbers to see what cars certain parts came on. Keep in mind however that realoem has been wrong before so if your information comes from realoem it is probably a good idea to get a second opinion. I like to use realoem for a primary source of information only if it is the only source, otherwise I use it to double check.
Terminology: below I use a few terms that may be ambiguous that have made things a bit fuzzy for a noob like me reading through other threads, this should clear up those terms for those out there that are like me. (Yes, I know it seems a bit elementary)
-output flange: the part that transfers power from the diff internals to the output shaft.
http://www.realoem.com/bmw/showparts...97&hg=33&fg=10
the part referred to is item 1 (w/o 2 and 3), which really has 2 main parts, the flange and the shaft. When I am referring to one of those specific parts of the piece I will specify, otherwise I am referring to the whole part. The link above is an output flange, the input flange is the same idea.
-output shaft: aka axle shaft or half shaft, the part that transfers power from the output flange to the wheels.
**Note- half shaft is not to be confused with drive shaft half
-diff: I am referring to the assembly as a whole; input/output flanges, carrier and everything inside.
-drive shaft half: the e34 drive shaft consists of a front and back half, unless noted I am referring to the rear half of the driveshaft.
The facts
1) The only diffs that swap in to the e34 using no custom parts (only off the shelf bmw parts, not counting subframes) are the e34 and e32 diffs. E31 diffs can work, they will need the E34/E32 rear cover and some drilling. See This thread. Diffs from previous or later generation 5 or 7 series or any generation of the 3 series will not work
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
3) Not all medium case diffs are equal (even apart from different ratios). I mean that medium case to medium case diff swaps are not completely a “remove and replace” process because input and output flanges vary between models. According to realoem the 525 (m50 and m20, auto and manual) shares output flanges with the auto 530 and auto 535s (86mm BC, M10 bolts). The manual 530 and manual 535s share a bolt pattern with all 540 and m5 cars (94mm BC, M10 bolts) although they use different size diffs.
So if you wanted to swap a diff from a 530 manual into a 525 (or vice versa) the output flanges from the original diff need to go in the diff that is being swapped into the car. All output flanges are interchangeable between medium case diffs.
Note: I have read that some people class medium case diffs as a medium-small, or medium-regular and medium-large. I suspect this has to do with the output flanges, and the overall width of the diff (distance between mounting faces of the output flanges), with the 525/530A/535A flanges installed making it a medium-small or medium regular, all others being a medium large. The narrower diff requires longer axles which is why 525/530A/535A axles are a different part number than other e34 axles. (These also have different bolt patterns from the other axleshafts as well) 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 output flanges are the same for all the large case diffs (except the 850Csi diff, it uses larger bolts and pattern IIRC) and share the bolt size and pattern with the manual 535 and manual 530 medium case diffs.
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. Moroza (post 53) and I recommend verifying what you have for an input shaft before you buy anything. I don’t have a great feeling about the info I found on realoem for this, and I know it was inaccurate for my car.
The input flanges for the large case diffs vary as well. The M5 and 750 input flanges use a smaller bolt pattern (86mm, M10 bolts) than the 540 and 740 (94mm BC, M10 bolts).
4) M5, manual 535 and manual 530 and auto 540s share half shafts. The 540/6 half shafts are very similar as well with the only difference being the diameter of the shaft, meaning they can be used as direct replacement. The 525 (m50 and m20), 530A and 535A use a different half shaft.
5) Diff internals will swap diff to diff provided they stay in the same size case. So the internals from the 3.23 525 diff will swap into a 3.07 530 diff since they are both medium case diffs.This goes for LSD units as well, no swapping from large to medium or vice versa. This really opens up the options for ratios to put in your diff since almost all bmw diff internals will work (e36 and many other cars use different medium case diff housings but the internals still swap into medium case diffs of the e34 and e32).Originally Posted by moroza
You need to be careful and do your own research if you plan to swap internals from a non e34 or e32 diff because apparently bmw made a few different medium case diffs with internals that are not compatible with eachother. They made what they called a compact diff and had a k (for kompact of course) on the diff tag if I remember correctly. I cannot find the post where I read this but I seem to remember the e39 was one of the series that the compact diff came in. I don’t remember if this was only a medium case diff thing or if it spread to the large and small diffs as well. Also something to be aware of is that there are 2 different LSD units for the medium case diffs. One unit works with the numerically lower ratios and one works with the numerically higher ratios. If I remember correctly 3.15 is the cutoff between the 2, but I cannot remember which group the 3.15 belongs in nor can i find that source of information again.
6) The large case diffs will bolt in to a medium case diff car, with compatible half shafts and driveshaft. Large case diffs are longer from the output flange axis to the mounting face of the input flange, and some use a different bolt pattern on the input flange. Some large case diffs (e31) use a different cover that will have to be changed, the e32 and e34 share diff covers.
7) Merged with 1) above
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. Do your own research on the process if you are thinking of taking this task on. See post 53 for Moroza’s experience and for torque specs (spoiler: 137ft-lbs according to Bentley)
TouringDan's method, see post 34 http://forums.bimmerforums.com/forum...ght=m50&page=2
9) It is sometimes possible to mix and match drive shaft halves. As far as I can tell all drive shafts for the e34 are mix and match-able except the 540/6 and 525s, and the 525s are mix and match-able with eachother. Large case diff driveshafts (with the exception of the 540/6) use the same splines (front end of the rear drive shaft half to the center u-joint) as the medium-large diffs. 540/6 uses larger splines and 525 driveshafts use smaller splines
The front half of the driveshafts are different lengths depending on transmission used, and the back half is different length (depending on diff size used) and also different cv-joint bolt size and pattern, depending of diff input flange.
apparently the drive shaft halves from the e34 (maybe all bmws, not sure) are balanced individually so you shouldnt have balancing troubles when splitting drive shafts and putting it back together slightly different (or mixing and matching halves). However there are those who have had and those who haven't had trouble with this.
see post 7
http://forums.bimmerforums.com/forum...ut+flange+swap
see post 38
http://forums.bimmerforums.com/forum...ght=m50&page=2
10) Exerpt from Moroza, Post 53:
Outstanding questions
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) Yes,see 'fact' 6)
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 "Fact" 1 or post 51 of this thread.
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.
See “fact 10) above.
4) Can the LSD portion of a diff (in the e32 and e34 cars) swap into the other size diff casing? I have read both that they can and can’t. I would assume that they can’t, just the same as regular diff internals can’t be swapped from one case size to another. see edit to 'fact' 5)
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)
Also noteworthy: Some bmws use torx head bolts between the output flange and half shaft cv's, the e34 usese a socket head cap screw, which is nicer for getting an allen bit by the cv boot and in the bolt head compared to a torx socket. However realoem and bmwfans.info both list the e34 bolt as a torx head bolt, and if you order from a dealer, or other online store (as far as I know) using that part number you will get a torx head bolt. There is a thread somewhere that outlines this problem and if I remember correctly, also gives the P/N for the correct SHCS. If you are a better forum searcher than I you may find the thread and P/N to order from dealership or online or whatever. Or you can buy from any hardware store using the following bolt spec (thanks 5mall5nail5): class12.9 SHCS M10 thread x 50mm length 1.5mm pitch
Last edited by dgoodsy; 06-14-2018 at 11:05 AM. Reason: corrections
Member
Holy wow. Need to spend a few mins reading this...
ITB COGNOSCENTE
Most epic 19th post ever.
________________________________
Nik
91' M5 3.9L Stroker
92' M5 3.8L
95' 540i6 Supercharged
95' 540i6 4.7 Stroker
95' 550i6 M70 Conversion
Member
Haha. I haven't posted much but have done a lot of reading in this forum. That post started out with a lot less info, but when you get looking into all e34 models rather than just one in particular it is amazing how many exceptions there are to the "rules".
BMW CCA Member
1. The input/output/axles are different between large & medium case diffs. But you can put a large case diff in a car that came with a medium case. If you've got a donor car you can get all that's different off that. I haven't looked at the specifics on all that's different between the 2 diff sizes. Might want to spend some time on realoem.com to see all what parts are different. Not sure why you need to change diff sizes though. A medium case diff will take a good amount of power.
2. An E31 diff works fine in an E34. They're all large case out of the E31. But the rear cover is different. Swap to a large case E32/E34 rear cover and you're good. Not sure what diff you'd want out of an E31 if you're looking for something around 3.0:1.
3. If you change to a large case diff you'll want the matching axles that went with that diff. Your J Spec 525 might use the same bolt pattern outputs. But a medium case diff is narrower than a large case. So your axles will be too long to fit if you install a large case diff even if they'll physically bolt up to the large case output flanges.
4. No, you can not install diff internals from one case size into a different case size. Medium case LSD will not fit into a large case. And the opposite is also true.
5. if you are going to change input flanges and not change the crush sleeve you will need to measure the current torque on the nut and torque the new flange down to the same torque the old one was torqued to. If you re-use the crush sleeve the flange nut has to be torqued the same or you will burn up bearings and ruin the diff.
Seriously not sure why you want to install a large case diff. Kind of a hassle to swap everything over. 5mall5snail5 runs a medium case diff and puts 688hp to the wheel as I recall.
I say stick to a medium case and get a 3.07 out of a 530.
Cosmos Black/Black 1995 540iA M-Sport
BMW Individual Exclusive Edition, 1 of 65 total, 9/25/95 Build
OEM additions include Euro trim, passenger seat mounted first aid kit, tool kit warning triangle, clears all around, black chrome exhaust tips, spare tire well gas can, and rear armrest fridge.
Waiting for install is an adjustable lumbar support, & drivers side glove box...
Member
1. the input flanges are different between large and medium case diffs (the bolt patterns and bolts are the same between some of the medium and large case diff input flanges)
while the output flanges are the different part numbers the non-525 medium case diff and all large case diff (e34 and e32, haven't checked for e31) output flanges, they do share bolt size and pattern. threads in this forum, and realoem confirm this. Also Threads in this forum, realoem and pelicanparts also confirm that output shafts are the same between the non-525 medium case diffs and large case diff cars. this would imply that the medium-large diffs and large diffs are the same width from output flange face to output flange face. ("fact" 3 from original post)
2.thank you, this is the kind of confirmation I am looking for.
3. No, my 525 did not use the same output flange bolts/ pattern as the medium-large or large case diffs, it used the same drive flange (part number) as other medium-large and large case diff cars. i have 525 axles that will not bolt up to medium-large or large diffs.
4) and 5). thanks again, I appreciate this.
For the record I don't want to put a large case diff in my car, and all of the "large case diff into medium case diff car" info above is not necessarily for my benefit or application. I would really like an LSD though, and it seems that the s3.15 from early 750s are the most available LSDs that are within the gear range I am looking for. That is the only thing that makes the large case diff option attractive, not because I think a medium case diff wont handle the power I hope to have.
BMW CCA Member
So you don't want a medium case s3.23?
Pretty sure none of the 3.07's had LS carriers. But you could get a medium case LS drive and install it in a 3.07 if you wanted. You'd have to re-set the gear lash if you did that though. That would require shims and special tools though.
Sorry I don't know medium case diffs better. I'm good with large case info though. Have 3 of those sitting here. Custom E34 3.56, E31 3.64, & E34 S3.91. Will either just slap the 3.56 into my M-Sport as-is, or get an LS drive out of a S3.15 and install it into the 3.56 and completely rebuild it.
Cosmos Black/Black 1995 540iA M-Sport
BMW Individual Exclusive Edition, 1 of 65 total, 9/25/95 Build
OEM additions include Euro trim, passenger seat mounted first aid kit, tool kit warning triangle, clears all around, black chrome exhaust tips, spare tire well gas can, and rear armrest fridge.
Waiting for install is an adjustable lumbar support, & drivers side glove box...
Member
I do want a medium case s3.23, but if a s3.15 came along local for dirt cheap I may get it and look for axles to make it work, and drive shaft. I am still looking into info for a drive shaft that would work in a 525 manual with a large case diff... unless I am missing something obvious it seems as though it would require a custom drive shaft. unless the back half of a m5 or 540 would mate to the front of the 525 manual drive shaft.
I should add to the post 1 that the large case diff is longer (output flange axis to input flange face) that medium case diffs and swapping from medium to large or vice versa will require a different drive shaft half length, and maybe cv joint. I have read that in some cases you can make the original drive shaft half work, but of course that is not doing it right.
Also good to know about the (lack of) s3.07, but that is the ratio i really want.
Don't be sorry, you have already added valuable information to this thread.
Member
can anyone paraphrase this into a sound bite. my Cataracts hurt
Member
i installed a s3.91 medium case in my 95 e34 530i 5 speed ......hate it.
/////////
Member
Im no expert on the matter but i've swapped diffs in plenty of E34's and E36's.
1. There is no Factory part you can use to mate a large case differential with a medium case driveshaft. The large case has a much larger input shaft spline diameter than a medium case, so you can't swap flanges between the two. That being said, there are 2 different E34 medium case input shaft flanges. 530/535 and 525 of both M20 and M50. There are also 2 different Large case input shaft flanges, E34, and E32. Not sure on E31.
2. In order to install a large case diff into a medium case car, you need not only the diff, but you need the matching axles AND the axle cups that go on the rear wheel hubs. They're held on with a 36mm socket and you'll need a puller to take them off(really, its easy).
3. The bolts are all the same, at least, i've never ever seen a different one. HOWEVER the bolt brackets, the 2-hole pieces that act as clamps are different from medium case to large case, you'll need a total of 12 of these pieces.
4. There is no large case Driveshaft that'll mate to a medium case transmission. Also, if you split the driveshaft, the spline dia on the large case driveshafts are much larger than medium case driveshafts.
5. Manual transmission and Auto transmission axles are different. 7 series use different lengths AFIAK. the 540iA axles are approx 3mm thinner than a 540i/6 or M5.
6. The way I swap flanges, and how bmw tells you to do it, is to mark the nut, and the input shaft and return the nut to close to the same point. I use a flat blade chisel and match the lines up, at least get very close. I have done this on 3 differentials and have yet to have a problem.
-Eric
Last edited by MazDuh; 12-05-2012 at 06:50 PM.
2 E34s. 1 E36. 3 Mx-6, 2 626, 06 Trailblazer SS, '73 Vette, 5VZ 4runner, and one insanely screwed up property tax bill each year.
BMW CCA Member
Yeah, forgot to mention if you went to a large case diff you'd need a custom driveshaft.
Options from cheapest/easiest to most annoying/expensive for you would be.
1. Medium case S3.23 (should drop in)
2. Large case S3.15 (custom driveline, different axles)
3. Medium case S3.07 (get a LS carrier from another diff & install into an open 3.07)
Cosmos Black/Black 1995 540iA M-Sport
BMW Individual Exclusive Edition, 1 of 65 total, 9/25/95 Build
OEM additions include Euro trim, passenger seat mounted first aid kit, tool kit warning triangle, clears all around, black chrome exhaust tips, spare tire well gas can, and rear armrest fridge.
Waiting for install is an adjustable lumbar support, & drivers side glove box...
Member
I had both e34 and e28 diffs side by side and found that,
1. They have the same dimensions.
2. The axles on my e34 535 interchange with my e28 axles.
3. The rear covers interchange.
4. The input flanges are different.
The only obstacle, then, to installing an a 3.07, 2.93 or even a 2.76 e28 diff into the e34 would be the front mounting points. You would need to fab up some good brackets and swap out the input flange or modify the subframe to accept the various and plentiful diffs from e30, e23, e24 and e28.
Another interesting tidbit. My e28 had a 3.46 medium case diff and I swapped to a 3.07 large case e28 M5,M6 diff with no problems.
cheers.
demet
Member
1. Has auto tranny and 4.10 diff
2. swapping to manual tranny
3. needs new rear gears.
4. many options and stuff like that.
nuff said
Member
Hate it because the gears are too short or is it a problem with the lsd and asc together?
1.
a)If I am not mistaken the medium case large input flanges (m50 manual and 530 manual, according to realeom) have the same bolt size and pattern and the mating cv joint (bolt size and pattern and number of splines) on the drive shaft are the same as the large case diff with the smaller input flange bolt size and pattern and mating cv joint (m5). also the grooved bearing that mates with the rear yoke of the center universal joint and the center bearing support is shared between all e34 cars except the 540. This means that they could share yokes, and if they do they might also share u-joints as well. IF this is the case it would seem to me that the driveshaft could be split at the center u joint, front half that mates with tranny used (up to the u joint) and the rear yoke and rear half of the driveshaft that mates with the diff used? (and therefore use a large diff in a medium diff car) As long as the center bearing support is mounted in the same place for all e34 cars would it not make sense, or am i reading too much into realoem?
b) I meant to imply that input shafts do not interchange between medium and large case diffs but i need to be more clear about that. the same goes for output shafts.
c)the differences in input flanges for large and medium diffs is discussed above in 'fact' 3 and they disagree with what you state. I am not sure if you are disputing what is above or just stating that there are differences..
for the record the 840, 840csi and 850 csi use the large input flange (94mm BC, m10) same as 540 and 740. the 850 uses the smaller one (86mm BC, m10). they all use the regular output flanges (same p/n as e34 and e32 large case output flange, same bolt pattern as medium case large output flange) EXCEPT the 850csi uses an even larger bolt size and pattern.
2. a) Are you saying matching axles as in axles from a large case diff only car? or axles from a medium-large diff or large diff car. Realoem, pelican parts and other forum members here would argue that axles from all e34s are the same, except 540 and 525. (540 have larger diameter shaft but right bolt pattern and length and ARE interchangeable, 525 axles use smaller bolt pattern, and different length)
b) I'm know what the axle cups are that you speak of, perhaps the drive flanges that are discussed in question 3) in the original post? if so do these cups have to match with the axles as discussed in 2.a) of this post (525 axles with 525 cups, non-525 axles with non-525 cups)?
3. I assume we are talking output flange here, no? I implied in 'fact' of original post, above that they all used the same bolts, just 525's have a smaller pattern. I should have been more explicit about that. Also the 2 hole clamps (reinforcement pieces, item 2 from http://realoem.com/bmw/showparts.do?...95&hg=33&fg=25 ) are 525 or non-525 specific, as with axles.
4. same as 1. a) above
5. a) axles or driveshafts? driveshafts are different (lengths and sometimes cv joint at the diff end of the drive shaft) between auto and manual cars, but axles are not. as discussed axles are 525 or non-525 specific.
b)yes the 7 series and 8 series use different axles than the e34, the 7 series are longer and the 8 series have a completely different outboard end. Also also the 540i6 axles are the only exeption to the non-525 rule, they are 3mm thicker that other non-525 axles (even the m5) but are the same length and are bolt in replacements. *( I have been referring to them as 540 axles above, but the 540iA are not the beefier ones the 540i6s got, I will edit that)
6) Awesome, thanks for the info. Should give someone the confidence to try it themselves.
1. I will pick up a s3.23 if there is one cheap (but Jon seems to have first dibs if one comes up) but i would prefer a 3.07 or lower.
2. the more I think about this, the more i am discouraged from doing it. (unless my far-fetched and long winded speculation about mating big case rear half with small case front half of driveshaft above is doable. Also i have a zf tranny and their drive shafts are hard to find, i may be doing the custom driveshaft thing anyways just for time's sake so....)
3.If I am going to open one up a diff put an ls carrier in I might just go with 2.93 or something even taller than 3.07. Again it depends what available, convenient and attractively priced.
the diffs you were looking at there, were they both large case or both medium case?
Also that is an interesting tid bit. I wonder if the large case input flange from an e28 might interface a large case diff with a medium case driveshaft in the e34? I am guessing that the e28 medium case input flanges or driveshafts are different, it seems unlikely that someone on this forum hasn't heard of or come across this yet if it were true. It is something to look into though..
I wish it was that simple in my head! haha1. Has auto tranny and 4.10 diff
2. swapping to manual tranny
3. needs new rear gears.
4. many options and stuff like that.
nuff said
Last edited by dgoodsy; 12-06-2012 at 12:35 PM. Reason: Automerged Doublepost
Member
Both were medium case diffs.
Currently I have a 3.23lsd in the e34 535 turbo but would love to have a taller gearset in there.
demet
Member
SO, since this is all very relevant to what I'm about to do it was a great read!
But can someone give me a simple straight answer on this:
I am putting a 420g 6speed in my 530i automatic. it is pre 9/93 build date, should have the 3.15 medium.
What drive shaft/flanges (if any without custom...uhg) do I need to make this work?
IF SOMEONE CAN ANSWER THIS IT WOULD BE AWESOME!
If it would help I have a diff out of my 89 535iA too, i wouldn't want the 3.91 though.
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'78 530ia-first car RIP 2005
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For the swap that I have planned, it is recommended to use the front half of the drive shaft originally with that transmission in (provided the trans came from an e34 as well) with the rear half on the drive shaft that is in the receiving car. I assume this means splitting the driveshafts at the center u joint.
However the difference between your trans swap and mine is that my trans came from a medium diff car and is going into a medium diff car. Your trans is coming from a large diff car and going into a small diff car. (i am assuming you have the 420g out of the 540, if it isn't then i think you have bigger problems than driveshafts and input flanges)
http://www.realoem.com/bmw/showparts...01&hg=26&fg=10
I am curious if the u joint center (22-rs from the link) used in the 540/6 drive shaft is bigger than other e34s. If it is the same size then i don't see a problem with doing the same as is recommended for my swap. If this is the case you won't have to touch you diff flange.
However if the 540/6 uses a different size center u joint then i am not sure there is anything you can do but get a custom drive shaft made ( I think you will still need to use the 540/6 front half and get the rear half custom, to mate with the input flange on the diff but also have the 540/6 splines to mate with the rear u joint yoke of the 540/6 front half)
can someone else chime in here, surely this 420g into a 530 has been done before...
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plzzz, I have everything figured out except exactly what drive shafts I need to use.
Remember I'm going from a e34 530 auto to a 6spd 420g and would LIKE to keep the medium case diff. I fear that may not be possible though.
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Wow...this is a very informative thread...thanks!
My plan is to use the buttery-smooth 3.46 LSD that came in my POS M20 auto. I am pretty sure it is not the original diff, that car was slower than I remember the M20 E34 autos being, so I can only assume it was changed out at some point.
Either way, I want that diff in the car, so here is my current plan for my '91 525a:
M54B30 (eventually) but for now, M50NV > E30 G260 (I have a few sitting around) > 3.46LSD and right now I have 255/35/18s out back, but will go to a 275 (I hate stretch!) so hopefully I will be right at the perfect 70MPH cruising RPMs.
I know the M50nv will be quite a bit down on power at those RPMs, but hell, I drive a M20 5 speed now...with 225/40/18 and 255/35/18s now, I am sure it will be quicker than the M20 car, right?
So, hopefully, come springtime, I will get the power and the economy I want. This diff post will make that a hell of a bunch easier!
Thanks
Luke
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Swap all the things!
I swapped a m62/6 speed into my 525 and kept the medium case. As far as i know there is no driveshaft that works, you cant just split the center and mix it up...
My local driveshaft shop wanted 150 cut and balanced so i went that route.
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With the driveshaft from a 540/6, the large case diff is a direct swap, providing the input flange is correct. I imagine they aren't that easy to come by though. your diff has a reasonably close ratio (should be 3.15 i believe) to the factory 540/6 diff (2.93), and of course shorter gears will give the car a bit more zip.
It looks as though the drive shafts probably can't be split as I was thinking, but regardless it will probably be easier (and maybe cheaper, some drive shaft shops do some work for very reasonable price) to get a custom one made.
You may need the front flange of the 540/6 driveshaft for a drive shaft shop to weld to the front of a shortened 530 driveshaft so it will mate with the flex disc of the 6 speed.
Well i have been a reader on here for a while, i figured it was about time i contributed something of substance! good luck with the m54b30 swap, I was considering that for a while as well. Also what is your perfect 70mph cruising rpms?
I assume you cut the front the front half of the 525 driveshaft? also what did you use for a front flange on the driveshaft, isn't the flex disc on the 6 speed larger than the one on whatever trans came out? Also why can't you split up the drive shaft and mix and match halves? was it a problem specifically with the 540/6 drive shaft mating with the 525 (or other medium case car) drive shaft, or problem with mating any different e34 drive shafts? I am almost positive the e36 guys do it when swapping trannies, (is there something different about the e36 driveshaft that allows that?) and I think TouringDan did it as well when he swapped in a s52 and zf... I should double check that though.I swapped a m62/6 speed into my 525 and kept the medium case. As far as i know there is no driveshaft that works, you cant just split the center and mix it up...
My local driveshaft shop wanted 150 cut and balanced so i went that route.
Swap all the things!
I had the flange taken off the e39 shaft and put on the stock 525 shaft.
From my memory the 540/6 driveshaft has a larger ujoint and different splines at that center section than the medium case e34's. e36's pretty much all came with the same engine so the shafts really only differ in length.
Props for getting all this info together by the way!
Last edited by mikeday1036; 12-07-2012 at 04:27 PM.
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Well, I might just be in luck then... Cause the guy that pulled the trans CHOPPED the drive shaft off after the trans flange instead of unbolting it...........
I also have an EXTRA 530iA drive shaft with a bit lower miles. so if its true I can find a place to make a custom DS for under 200 that works just fine.
Yea Id like to just keep my 3.15 medium, the cost and likelyness to find a large case lsd at the ratio I want within a month is pretty out theyre.
Slowly climbing the ladder. But never reach the top.
Click Car 4 Build!
'86 325es-Turbo m30!
'94 325iA-Clean DD
'94 530i-6 Spd swp
'89 Cherokee 4x4-4.7L stroker
'97 Eclipse Spyder-4g64/63 stroker Turbo.
'89 535is-RIP 2020, engine now in e30!
'84 318is-RIP 2016.
'89 535iA-Parted 2012
94' 530iA-RIP 2004, engine in new 530i
'78 530ia-first car RIP 2005
Member
That sounds good except autos are significantly longer that the manual transmissions (for the 525s they are anyways), and use much shorter front drive shaft halves because of it. I imagine your 530A front drive shaft half will be shorter that the 540/6 front drive shaft half, and wonder if it causes much trouble if your drive shaft shop will have to lengthen the shaft. (I think they do it, but I have never had it done)
edit: Post 1 updated with new info, Thanks to those who contributed answers and those who ask questions that encourage discussion. It all helps get info into this thread. And for those who haven't shared their experience, don't keep your knowledge secret, share with us!
Last edited by dgoodsy; 12-10-2012 at 02:04 PM.
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