I was looking at a 60's fleetwood and it wouldn't shift until you floored it. It didn't shift hard. When you when from drive to reverse, it shifted smooth. Wondering what it could be. He said it was a simple fix.

 

Possible stuck governor weights or a stripped gear on the governor. Necc to remove to verify. Accessed once the tin domed cover is removed. Requires snap ring pliers to get cover off. Have a tranny shop point it out to you.