Pondering E36 M3 Evo diff

Alan
The US diff folks suggest that E46 M3 has the big case
http://metricmechanic.com/pdfs…-differential-booklet.pdf

but as martinw points out, the actual case castings can have quite different exteriors !

Birds just quoted me GBP 360 for a 3.45:1 crown wheel and pinion set (if that helps!)
Cheers Keith

How does the variable diff work? I thought there was some electronics in there, but maybe it's fully mechanical?

If the unit inside is the same physical size and has the same layout as all other large case diffs, you can simply swap it into your case. I swapped the diff internals from an E36 M3 Evo into my mate's E34 540i, as it was less hassle than changing the input etc on the E36 unit (he wanted to keep same gearing, so I just swapped the crown wheel from his open unit onto the LSD).

Zitat von mattsimis;72731

From reading up on the E46 M3 Diff, the "M Variable Diff" is fully mechanical, it utilises an internal sheer pump (non serviceable). Its a Viscious Fluid based diff.
Ive read about at least one guy putting it into an E36 M3. Apparently its considerably better than a locked LSD in the Wet and Snow (and Mud etc), which would be very much appreciated here as you can imagine!


Maybe a stupid question, but would a non-diff specialist (but good mechanic) be able to swap the internals between the diffs? Is there anything he would need (seals etc)?

Short answer would be yes, he would need new seals, crush washers and if you're doing the job properly you might want to look at new bearings. If it were me though I would prefer to get it done by a specialist, setting up the diff preload properly is crucial and if not done properly the diff will wear rapidly. I would recommend Bird's, they fitted my Quaife unit last year and the workmanship is first class - also not exorbitantly expensive.

Zitat von Argonaut;72739

Short answer would be yes, he would need new seals, crush washers and if you're doing the job properly you might want to look at new bearings. If it were me though I would prefer to get it done by a specialist, setting up the diff preload properly is crucial and if not done properly the diff will wear rapidly. I would recommend Bird's, they fitted my Quaife unit last year and the workmanship is first class - also not exorbitantly expensive.

Good point regarding the preload, although note that it's only necessary to do this if the input drive (pinion) is removed. When I fitted mine to the 3-series, I was happy with the original gearing, so I just swapped my original crown wheel onto the LSD unit, which meant I could leave the pinion in place.

I replaced the output shaft bearings on mine, cost me about £20 for the pair I think, although I know someone in the trade. Bank on double that if you buy them from BMW.

Zitat von mattsimis;72731

From reading up on the E46 M3 Diff, the "M Variable Diff" is fully mechanical, it utilises an internal sheer pump (non serviceable). Its a Viscious Fluid based diff.
Ive read about at least one guy putting it into an E36 M3. Apparently its considerably better than a locked LSD in the Wet and Snow (and Mud etc), which would be very much appreciated here as you can imagine!

Interesting. Presumably it'd only fit in an M3 Evo, as the 3.0 M3 had the medium case diff. Saying that, you can change the entire subframe to that of the Evo, and use the larger diff...

I wonder if there are any other mods required to fit, or if it just fits right into any large case diff.