Slips out of gear. This condition may be caused by weak or broken shift-rod poppet springs, a bent shifting fork, or excessive wear of the gears. The transmission must be replaced or repaired.
If you have a WW2 jeep with a T-84J transmission then you might want to purchase my book, Trouble Shooting And Rebuilding The T-84J. Army Jill never leaves home without it, neither should you!