I backed my vehicle out of the garage. I started it up a few minutes later, put it in reverse Nothing, the column shifter did not click into gear just moved freely. I checked the linkage and everything was fine. I then disconnected the linkage from the transmission and tried to move the selector. The shaft moved very easy without clicking. Before I remove the pan, what should I be looking for?

Thanks.

 

The "rooster comb" has came loose inside the transmission(nut that holds it to shaft came off) Easy fix-this happened to the th350 in my '69 camaro

 

Much appreciated.
Thank you.