FWIW, I just replaced a set of original axles with DSS from Auto house AZ that a friend bought for his car. $100 each. The new axles lacked about 1/4" of the articulation the originals had, making it impossible to get them in without removing the inner trailing arm bolt to pivot the arm out to make room. Disassembly took 45 mins.; reassembly took 3.

Also, Amsoil severe gear 75w90 is what I used, and I have every confidence this lube will be the last reason the differential grenades. The synthetic gear oils of today are light years ahead of what would have come in our cars originally so going thicker isn't necessary.

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'82 300CD
"Pearl", the very first turbo diesel 123 coupe
Totaled 11/23/18, rebuild in progress.
'85 300TD, "Artemis".
'78 300D euro, "Ol' Red", mostly retired.
'85 300D, "Gandalf".