Differentials: Difference between revisions
Created page with "== E28 Differential FAQ == ''By @MikeW - originally in this [https://mye28.com/viewtopic.php?t=44635 post].'' === What came in mine? === It depends. All 533/535 came with 3.25 ratio diff's, some with Limited slip, most without. 82-87 528e[i]s[/i] (model year, not production date) came with 2.93s, again, some with, most without LSD. M5s came with 3.91 and limited slip. 88 Model year 528e''s'', also known as Super e''s'', used 3.25 with 5 speeds and 3.46 with auto..." |
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=== What doesn't work? === | === What doesn't work? === | ||
No diffs from Bavs, E12s, E9 Coupes, 82 and earlier E24s will work, they are all a sideloader diff and mount completely differently. 81 and earlier E23s I don't think will work, even though they look similar. No diff from a 4 cylinder E21 or E30 will work, except M3s. | No diffs from Bavs, E12s, E9 Coupes, 82 and earlier E24s will work, they are all a sideloader diff and mount completely differently. 81 and earlier E23s I don't think will work, even though they look similar. No diff from a 4 cylinder E21 or E30 will work, except M3s. | ||
=== Additional Resources === | |||
[https://www.mye28.com/viewtopic.php?t=142750 FAQ Medium Case Diff Rebuild] | |||
[[Category:Tech FAQ]] |
Latest revision as of 15:20, 31 December 2024
E28 Differential FAQ
By @MikeW - originally in this post.
What came in mine?
It depends. All 533/535 came with 3.25 ratio diff's, some with Limited slip, most without. 82-87 528e[i]s[/i] (model year, not production date) came with 2.93s, again, some with, most without LSD. M5s came with 3.91 and limited slip. 88 Model year 528es, also known as Super es, used 3.25 with 5 speeds and 3.46 with autos.
What can I use in mine?
Most E28, 82 and later E23, 83 and later E24 and 6-cylinder E30. Note on the last one, only the 6-cylinder cars, with the exception of M3s.
The Z3 torsen-based diff will work as long as the rear cover is replaced.
What had what ratios?
The following are all for US spec cars.
Car | Ratio |
---|---|
All 533/535 | 3.25:1 |
82-87 528e | 2.93:1 |
88 528e 5 speed | 3.25 |
88 528e auto | 3.46 |
325e | 2.93, though there may have been some 2.79's in early cars |
83-84 633 | 3.25 |
82-84 733 | 3.25 |
85-87 735 | 3.46 |
85-87 635 | 3.46 |
88-89 635 auto | 3.91 |
88-89 635 5 speed | 3.64 |
89 on 325i auto | 4.10 |
325 5 speed, all | 3.73 |
M3 | 4.10 |
82 etas and E23s seem to have had a unique housing and cover plate that limits their interchangeability; however you can still use a later assembly in those cars, but you may not be able to swap cover plates.
One small problem with using an E30 diff in an E28, you need to change the rear cover and the drive flanges. The rear cover comes off easily, but be prepared, you may need a new gasket, the drive flanges also come off easily, but clean up around them first so you don't drop dirt in your nice new diff. The flanges "pop" off, you will need a screwdriver or two or a small prybar or two. Get the lever under the flange and give it a little pop, more probably than you can do by hand, but not all that much. There is a snap ring in there that locates it. Reassembly is similar, sometimes they don't want to go in, they should slide most of the way in by hand fairly easily, but you might have to play with them some to get them aligned, then once they go most of the way in, you have to pop them back in place. The drive flanges on all the 5/6/7 series cars above are all the same.
Rear Covers
Early, as in 82, may be unique, as I mentioned earlier. 83-84 are interchangeable for 84 and earlier cars with the early type square diff mount. 85-88 rear covers fit the later cars, and you can mix and match the housings and the covers between 83 and 88. E28 and E24 cars use the same covers in the same years. E23s look like the later cover, but are different, they are somewhat longer. I've heard of people cutting a deeper mounting hole in the cover flange, but I wouldn't. The right parts are too cheap and easy to find. E30s use a completely different type of cover which doesn't even come close to fitting, but the diff does.
Limited slip.
They are marked with an "S" both on the ID tag on the diff which is mounted with one of the rear cover bolts, and with a paint mark on the top of the diff, a big "S" in white paint, which by now can be sometimes hard to read. The ID tag on the cover will have the "S" in front of the ratio, such as "S3.73". It can be very hard to read as the years go by and the tag rusts, I've had the best luck in kind of polishing them on my pants leg to clean them up to read them.
The "Big" diff.
These came on M cars and euro 3.5s.
Large case differentials are a little bit longer than the medium case differentials. Swapping between them is a non-issue in terms of halfshaft angle and fitment to the subframe in an E28 or E24. Although some have said that one needs to elongate a pair of holes on the subframe, I've never seen it or had to do it - my experience has all been for MY83 and later cars.
Big Diff interchangeability:
3.91:1 (US E28 M5, US E24 M6)
3.73:1 (Euro E24 M635, Euro E28 M5)
3.64:1 (Euro E24 635s)
3.45:1 (Euro E24 635s)
3.25:1 (Euro E28 3.5 engine, Euro E23s)
3.07:1 (Euro E23 745i)
2.93:1 (Euro E23 745i)
...*more fitments/interchange to come*
Cover for large case differential:
Required cover for E28/E24 fitment:
PN 33 11 1 210 668
Interchanges with:
E23 733i SEDAN, U.S. (up to 9/81 build date)
E23 735i SEDAN, Euro
E23 745i SEDAN, Euro
E23 728 SEDAN, Euro
E23 728i SEDAN, Euro
E23 730 SEDAN, Euro
E23 732i SEDAN, Euro
E23 733i SEDAN, Euro
E24 M6 COUPE, U.S.
E24 635CSi COUPE, Euro
E24 M635CSi COUPE, Euro
E28 M5 SEDAN, U.S.
E28 535i SEDAN, Euro
E28 M5 SEDAN, Euro
E28 M535i SEDAN, Euro
re: swapping LSD units in big diffs:
1. You will need to have the right tools and factory service manual, as stated above, since you need to remove the ring gear to swap out the LSD unit.
2. The big case LSD units are all interchangeable. There is no difference in the LSD case.
Koala Motorsports is one of the best, if not the best, rebuilder of differentials at the current moment. Cost is roughly $1400 to rebuild a LSD unit, and comes with a 3-year unlimited mileage warranty (as of March 2008).
FYI, parts cost (clutch disks, spacers, seals, bearings, etc) to rebuild an LSD are approximately $400-600 (see diffsonline.com). The majority of the cost of rebuilding a diff is the tooling and experience you get from professionals. You can no longer get a lot of the parts from BMW anymore, and most of the professional rebuilders source them from other places.
What doesn't work?
No diffs from Bavs, E12s, E9 Coupes, 82 and earlier E24s will work, they are all a sideloader diff and mount completely differently. 81 and earlier E23s I don't think will work, even though they look similar. No diff from a 4 cylinder E21 or E30 will work, except M3s.