Just for giggles, next time the car is good an warm check the tranny fluid level. My 4.5 would make a groan/moan once and a while when starting from a stop, sounded like it came from the rear and took forever to pinpoint. Than one day it sounded like it came from the tranny, check the fluid and bigger than Dallas the level was down about 1 pint. Topped up and no more groan/moan.
Your results may be different.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.