it is probably sift linkage go under the car and move them by hand and check it .the factory shifters on saginaws are just short of junk when new when they get some miles (and a few gorilla shifts )on them they will do really strange things.also a lot of the problem on some cars is the fact that the shifter mounts to the floor pan instead of the tranny so when you gas on it it twists the linkage so hard that you cant shift till you let up on the gas.
