I just got done putting a new clutch in my friends ranger and now the trans will not shift. if the truck is started in 1st gear and the clutch is applyed the truck will move but when i go to put it in 2nd gear it just wont go into gear. The weird thing is if the car is off it will shift in evey gear fine. If the car is started in nutral it also will not shift gears. anybody know what the problom could be?

Probably need to bleed the slave cylinder again , these are notorious for being hard to get the air out. that would be my best guess