I did this torque tube rebuild last summer to my 54.
Like many other things in the 3100 54, it is distict from all the other ADs.
If you do the 355 gear swap, you will need the ring gear housing piece from an earlier AD. Patrick will tell you about this when you get ready to buy the kit.
The 54 is a 390, the earlier 3100 ADs are 411. Makes all the difference in the world on how your AD drives. Quieter, faster, cruises nicely at 60-65 mph.
