Diff Project

[82eye]

Finding an LSD out here is rare. Finding one in a gear ratio you actually want is impossible. Been looking for a 3.73 ls for quite some time. So decided to build one.

Cracked a 3.73 open, checked it for wear and lash.


















contact pattern and lash was good so went ahead and pulled it apart. took the speedo chopper and crown gear off.












cleaned the case and axles up then hucked some paint at stuff









side covers got new axle and flange seals. fancy seal puller in action..










all cleaned up







got a 4.10 LSD and cracked it





checked lash and all was good so pulled it





broke the top cap and crown bolts in the vice then popped the speedo wheel and crown gear












took the ls apart and cleaned everything up for a rebuild.







gear stack gets built in reverse when pulling it from the carrier housing. housing ..






add gears one by one..






completed stack





had some goodies shipped in













installed new axle clips in the ls carrier and top cap





old clutches were shot. comparison with the new clutches. old ones are scored and very shiny showing wear.










everything gets put back together wet





gear stack housing faces are friction surfaces so they got refaced to remove the glazing and provide a fresh surface.


before





400 grit wet / dry laid flat





after. won't be perfect but should work as original.





got the ls unit all back together. the last few bits need to be installed in the top cap then wired together thru an inspection/oiler hole to keep it all together.









all back together. used four of the old top cap bolts to snug it to the point i can remove the wire.






today the top cap bolts, 3.73 crown gear / bolts are getting installed and torqued up. maybe get it back in the case if time.

[95BMWIC]

Thanks for this - I appreciate the visuals on the internals of the LSD. I have 2 "spare" 4.10 myself and want to eventually crack them open and refurb if needed.

[spdracrm3]

Good times ,nice work

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[82eye]

got the new top cap bolts all torqued in.





then got the dead blow hammer out and carefully tapped the 3.73 ring gear on to it's new home. got it far enough to engage some threads on 5 of the old bolts, then carefully wrenched them up. marked the old bolts to identify them.






then torqued in all new crown bolts






got a speedo chopper wheel install kit








all together







hucked some color at the diff cover. horrible conditions. like painting with water lol.






stuffed the ls into it's new home. then checked lash.






i gained a point at 0.0030 and all was good. installed the axles and measured lash again with the same result. took another contact pattern but cleaned it all up before thinking to take a pic. crap. it was great tho lol.
shellacked up the diff cover and installed the Crappiest Gasket Ever






made it work tho then installed the diff cover and this..






was saving it for a bit and the diff had earned it.


put a new o-ring on the speedo sensor and installed it. then just stared..











bmw lsd diffs can sometimes be identified by a painted S on the diff case

[Kershaw]

Very nice work!

[TheStigg]

Great effort and excellent documentation, one for the archives. Thanks!