With the shift lever off the trans shifter shaft, install the lock nut on the shaft. Use it to manually shift from forward to neutral and reverse by trying to spin the input shaft/ secondary clutch (with the belt off). if it does go into gear and neutral, carefully alighn the the shift lever "dot" with the corresponding "line" on the shifter shaft. Several times I've seen the reinstallation of the lever incorrect and this can cause the "push/pull" operation of the cables. It can also lead to the cables not being in the proper relation to the forward shifter cam. If you can not shift it manually, then yes the trans would have to be split apart. Do not forget a new gasket if it is taken apart for inspection. Good luck
