Longtime lurker, first time poster. My apologies for this first post being cross posted at another forum--it seems like there is a lot of resident knowledge here about differentials.

I am in the middle of a big rear end rebuild project on my 1985 300TD. Basically everything from the transmission back is getting refreshed: flex discs, driveshaft bearing, all bushings, axles, SLS delete, etc.

I stopped by the Pick-n-Pull today and picked up a 2.47 differential from a 1983 500SEC (W126). It appears to be in great shape, with no perceptible gear lash. I am going to swap this in while, as they say, I am in there.

My questions are:

1) What shims from the current W126 axles do I need to retain for when I put the W123 axles in?

2) Should I just take both diffs to a specialized rear end shop to have them swap the input yoke in, or should my mechanic be able to do it?

3) Do I need to worry about lining up the new differential so that it is coaxial with the driveshaft and transmission? I read an earlier post where a member spent some significant effort putting washers in the diff mount, the center bearing support, and even the trans mount in order to get them all pointed at each other correctly. Seems like it makes sense. What happens if I just bolt it up? Any experience with a diff swap from a W126 gasser?