ponchox9

Hi, okay so i took out my gsr tranny to install a new input shaft bearing and seal and also put in a new clutch and flywheel. everything seem to be working fine. but when i start the car it is hard and wont shift into 1st and 2nd and reverse. the rest go in no problem. with the car off all gears are easy to shift into reverse is kinda a pain. I put the car back on stand and found out that with the car on the jack stands it shifts into all gears just fine with car on or off. why is this? could it be my master cylinder?