I'm guessing that the noise issue is not trans related. More likely driveline play or loose differential mounts.
It will be hard to replace the modulator without dropping the rear. We adjust them without dropping but its a little of a trick in the 201 body. Not much room.
I adjust numerous modulators every week. I replace them commonly on rebuilds but I have only seen a few bad ones. I would say less than one a year for near thirty years. Thousands and thousands of adjustments. There is a real good chance I will make some form of modulator adjustment on every 30k service we do and on older diesels even more often than that.
Bosch Master, ASE Master, L1
33 years MB technician