Sounds like either the shift keys are worn, or the internal notches in the gears are worn - assuming that your linkage is okay.
At a standstill, engine off, does it feel like it's going all the way into 6th? Maybe the linkage needs to be adjusted, or the sheet metal is blocking its full travel.
At a standstill, engine off, does it feel like it's going all the way into 6th? Maybe the linkage needs to be adjusted, or the sheet metal is blocking its full travel.