[unimog]

Hi,
I had a similar problem with my 1952 401. I used Mike Robinson in Manchester (Mob 0775 3609 222) and he stripped and rebuilt my gearbox 3 years ago and fitted an overdrive + a remote gear lever for me.
It is now great, with smooth slick changes, no rattles and no play!
(after 60 + years in the car, many of my gearbox drive components were simply worn out!

Gearbox and overdrive come out and fit back together, but you need 2 strong men. ( My wife was not quite up to helping with the lifting out of the unit!)

Mike also supplied all new floor panel bolts for me to reassemble the floor panels, I applied copper grease to all bolts to make future removal easy.

He also supplied a 300mm longer speedo drive cable to the overdrive, as it was a bit tight in its route, speedo needle was prone to fluctuation and swings, and the cable was very close to the hot mild steel exhaust.
I re-routed the cable into smoother, gentle radius and wrapped the cable where passed over the exhaust with some heat insulation wrap.

I have had no issues with gearbox or overdrive since and now motorways at 60ish is a pleasure,

......although my original click- out trafficators refuse to pop out (or go back in) at these speeds ( wind pressure, I guess ) so I retro-fitted flashing indicators, front and rear, for my peace of mind.