all the other gears work fine, but first, i ws told not to be hard on the shifter because i will riune the nylon bushings in between the gears. so if i back up and need to start off i try and go to first gear and it just won't go in. so i go back to reverse and try agen but still won't work. then i go through all the gears and sometimes it will work. what it rong with it?? and how do i fix it??