OK, so I originally replaced the cable in 1st gear (which as it turns out is the wrong gear to start with). Anyway, with the grip shifter I had to partially take it apart to put in the new cable. So I put it back together, try it out and it shifts up fine from 1 to 8. But when I wanted to go down, I went from gear 8 to 7 and could no longer move the grip shifter. I thought the problem may have been putting it together in gear 1, so I tried again in gear 8, as the manual says. Well the same thing happened on the down shift. I went from gear 8 to gear 7 no problem, then the shifter got stuck. It's not a tension problem, because even if I take all the tension out, the shifter still won't budge.