Sideloader is a 188mm?

[Lock]

Discussing this with forum member Eric, I'm pretty certain the sideloader center, ring and pinion are all the same 188mm parts as in the e28/e30/e34/e36 despite the different case shapes. Why does anyone care? Because it means if it is, you could upgrade your open sideloader to LSD by using a center from a newer 188mm without having to spend thousands on a rare, worn-out LSD sideloader.

Evidence for this is that in realoem (assuming it's accurate), the lsd discs and clutches are the same part number.

https://www.realoem.com/bmw/enUS/showpa ... Id=33_0053

Also, the pinion bearings and carrier bearings are the same parts too.

https://www.realoem.com/bmw/enUS/showpa ... Id=33_0037

I took apart my old sideloader and measured it, it's almost exactly 150mm end to end, which lines up with schematics I've seen. I don't have a spare 188mm from an e28/e30/e34/e36, but if someone does - lsd or open - please measure the length end to end. If so, then it should be a drop-in assuming the stub axle splines are the same count, size and length.

And it seems likely that the ring gear would also bolt up, barring any shape differences. Or, you could use the newer ring gear set as the pinion appears identical.

[Mike W.]

I've suspected that for years but never really dove into it. At one time I had plenty of surplus spare diffs, worth next to nothing and could have explored, but no more.

However... Now I don't know how critical it really is, I suspect it's not really as touchy as it's made out to be, that machining is pretty close to identical, but a big deal is made about setting up diffs. Both pinion placement and especially ring gear lash. Very few places even try to set up a diff.

And the 80s diffs that were once so popular in Es 23, 24, 28 and 30 are now themselves over 30 years old with who knows how many miles on them.

But if you do the swap and it works, by all means let us know. I myself want to know just for the curiosity factor.

[Lock]

Mike you're right, there could be some minor differences that make this unrealistic. I wondered why in the 30+ years the sideloader and next gen diffs have existed no one has done this. Maybe people have and just didn't write about it on the internet. Either way it's unfortunate I think I'm about 10 years too late. e34 LSD centers are now at least $500 up to $1000, before a rebuild.

Setting up the tooth contact in a sideloader must be a real pain as you can't see the contact pattern without opening it up again, potentially changing the settings you're trying to set. And with carrier bearings being set by shims (which seem to be NLA), not threaded nuts even more of a hassle - even though carrier bearing preload is fairly forgiving. No idea how you are supposed to measure backlash which is important.

If I get a newer center working in there I'll repot back. I could probably get a cheap e30 open center for $50 off ebay, worth a shot to just prove if it works. But now the carrier shims are NLA, might have missed the boat on getting them set up well.

[tschultz]

Sounds interesting... but I have a number of open diffs. The lsd ate harder to find, though I do have one that whines and seems like it would be a candidate for rebuild somehow.

[Robert Bondi]

I just sent off a 3.64 open diff for rebuilding to Metric Mechanic. I did the same about 20 years ago for my 530i and I'm still running it.
Nothing fancy...I just hate things that leak.

https://metricmechanic.com/differentials/#

Between this page, the downloadable pdf, or talking to Jim Rowe himself, I bet he'd know the answer.


Robert

[Lock]

I just sent off a 3.64 open diff for rebuilding to Metric Mechanic. I did the same about 20 years ago for my 530i and I'm still running it.
Nothing fancy...I just hate things that leak.

https://metricmechanic.com/differentials/#

Between this page, the downloadable pdf, or talking to Jim Rowe himself, I bet he'd know the answer.


Robert

You're right, Jim Rowe would probably know, given Metric works on those diffs and has them all out in the shop.

From that doc, I'm going to guess the ring and pinions are interchangeable given the number of identical ratios available that match the upper set of ratios available for the e28/e30 etc.

That would also explain how MM are able to build sideloaders with ratios that were never offered by the factory.