after changing the casing, the tranny wont shift.

heres the story.

baught a ls tranny with the casing off so we can see the condtion of the gears. everything was good. got home. shifted the forks to see if everything was in good working order, sleeves were moving freely..good. bolted the casing on. and threw it on the motor. attached the shift linkage and it wont move...!!!??? i dont even know if its in gear? got back under the car. removed the shift linkage, and tried to twist/push/pull the piece where the linkage connects too, it wont move.

i have searched and asked some ppls. and most say it might be around the shift assembly. i am taking it apart this weeken, so any idea will be looked upon.