Hi John: Your right about the input shaft update! quite expensive the reason is the early units only had a bushing between the input shaft and output shafts and after 100k they wipe out and the rear of the unit looses lube causing torrington bearings to fall into planet sets distroying the unit.The newer versions have a needle cage type.You can get the original bushing seperate for About 20 bucks! and replace those torrington bearings.Thats what I did on my 97 S500.
Good luck Tim