1960 Merc, difficulties in engaging drive

[Vapiti]

Hi, I have 1960 Monterey, 383 + dual-range MultiDrive. The problem that I have, and one that's gradually gotten worse is that with cold engine/tranny any of the three forward drive modes do not want to engage. I need to warm the car up for 5-10 minutes before the tranny will engage. After that it works fine.
Engaging reverse, no problem cold or hot. Oil level correct, oil looks clean red and has no burnt smell. Where to search for fix? As it is working fine once warm, I'd suppose there is no fundamental failure but perhaps some adjustments needed.

[FirstEliminator]

Hi,
I see it's been a while since you've posted your question. To me it sounds like the rubber in the trans is getting brittle. What happens is the rubber o-rings and seals deteriorate after so many heat-up and cool down cycles. The rubber becomes harder and shrinks. After the engine is running for the 5 to 10 minutes the trans warms a little bit and the rubber becomes plyable and begins to seal. The trans usually works good for the remainder of the day as it doesn't fully cool down, like as if it were sitting over night. All in all. The trans needs a rebuild.