I have a broken wire that wants to connect to some kind of sensor near the rear differential. Can't seem to find what this part is or does, name and/or part number would be great. Thanks.

Almost assuredly, that wire is the signal for the ABS system. M/B uses a single pickup in the rear on the older vehicles, making the assumption that both rear wheels are spinning at the same speed.

Much appreciated Brian, makes sense to me.