From what i have read on this transmission, this is a fairly common problem, although the shutting it off and turning it back on kind of threw me. It is not computer controlled in any way, and has no electronic parts, so it's not like rebooting or anything. It must be that shutting it off just drops the RPMs enough that the parts start to mesh again (so I guess it is kind of like a reboot
Your transmission likely has a busted "sprag". I have no idea exactly what that is, but it sounds clutchpack related, and means you need a rebuild, likely with some new hardparts.
If your TV cable and brackets are all original, and the book does not show your setup, find the common denominator of the different setups.. like, full and complete cable retraction at wide open throttle (like on the GM's). or find another book.
But this "sprag" thing is likely your problem. AAMCO does a free testdrive and diagnosis related to said testdrive, at most of their shops, or at least they did a couple of years ago. Any diagnosis beyond the testdrive is going to cost you some greenbacks though.