I'm having trouble with my Silverado I cant seem to shift properly from 3 to 4th gear i have an automatic I've tryed cleaning my air mass flow sensor but still nothing I've also used Lucas oil transmission slip and nothing , any ideas what it could be ? I'm not trying to get a rebuild till I know its really needed other than that truck works fine just those gears sound as its in neutral as I press the gas going from 3 to 4th