78vette

My 78 L82 4sp was being towed using a dolley (rear wheels on the ground) when a box hit the shifter and apparently put the car into gear. Looked like 2nd to me but after I got the car off the dolley, I found that Reverse, 1st and 2nd appear OK but when put into 3rd or 4th, the tranny whines like an automatic about to die and the car does not move.

Any ideas befoire I begin dissasembly?

Thanks,

Mike