Maybe its the "4th gear timing adjustment mechanism" thats out of whack.

Isn't there a vacuum line(s) running from the distributer up to a small box 
attached to the top of the engine compartment? I can't remember which way 
it alters the timing, but it gets an electrical signal from the tranny 
that opens/closes a valve controlling the aforementioned vacuum line(s).

David Schwarze help me out here ;)

Alistair