Long story short my 2001 silverado 4x4 4l60 bit the dust I replaced trans drove the truck no issues until rear-end went out after about a month get rear-end put in now truck will not shift unless I do it manually

 

More details of what you mean shifts manually ?

 

Is is possible the electrical connector to the trans was not re-connected?

Frank: Am I correct that without the electrical connector, while the trans normally starts in 3rd, you can manually downshift it into 1st or 2nd? If true, maybe the OP only has two gears then.

 

Yeah need more info, with connector unplugged he would have manual 2nd and 3rd only, But a rear end failure could have busted the low roller in which case it would not move unless you started in manual low 1 then would manually shift up through gears. But as I ask him need more info ,