Transmission slipping..

The Tranny on my new 73 satellite slips..Its an automatic TF-904 I believe. going to get under there late and make sure.

but the previous owner fabricated up his own kickdown linkage. could this be the reason that it has trouble shifting from 2nd to 3rd gear?

I've seen the Kickdown cables that lokar sells, and i'd have no problem getting that If I knew that that would fix the problem.

Does it make sense though that if I put a new kickdown on there it should solve the problem?

or what other stuff should i check? again it slips between 2nd and 3rd gear only. once engaged in 3rd gear though, it has no problem at all driving..

thanks..