redtruck65MA,
I assume you are talking about a side shifted trans,saginaw 3spd,65-73 ? If so are you sure the rear reverse lever is engauging all the way to the detent stop? If you have removed the levers and manually engauged and it still pops out you will have to remove the cover and forks.You could have a shift fork that is worn to the point it will not move the syncronizer all the way into gear or the gear is worn.You can remove the cover realitivly easy.Drain the fluid and put both levers into neutral.Unbolt the side cover and remove the cover and forks as one assembly.If you don't feel comfortable removing then someone with transmission experience may be in order.Good luck
