the plastic drive gear thing repair is for a 722.4 (later model diesel W124) - and with that you have a transmission that wont shift out of first gear.

this case sounds like a 2nd brake band not engaging. A smart mechanic can remove the band piston and check. At this mileage its a hit or miss as the entire clutch train in the transmission could be worn down badly.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)