It shifts really hard and it seems to stick in 3rd gear

I own a business that installs Remote Starts, in 1995 G.M. Added a 2nd Ing. Wire that must be powered during remote start operations. This circuit supplies the Transmission Control Module and Shift Solenoids, which if not powered will cause the Powertrain Control Module (PCM) to set a fault code and your check engine lite should come on. In remote start applications the Primary Ing. Wire (pink) the Secondary Ing. Wire to the H.V.A.C. Controls (orange) and the third Ing. Wire to power the Transmission Control (white or pink/white) wire must all be powered. To do this you must add extra relays to the remote starts Ignition #2 Output to power these circuits.