When I put my truck in drive and take off, it shifts from first to second without any problems, but when I go from second to third, it revs up about 500 rpm(kind of like when you put the clutch in while you've still got the gas pedal pushed) then shifts into third. The only time it does that is when I'm shifting from second to third. Other than the revving sound, there are no other unusual sounds coming from the truck at all. Sometimes when I'm driving, the O/D light will flash and the truck with forget that first gear exists. When I take off from a dead stop, It feels like I'm taking off in second gear. I don't remember if I have the same problem with it revving up between second and third after that happens, but it shifts normally after I get going, I think. Does this sound like something that is not going to cost me $2000? Would it make any difference if I changed the trans filter? I checked the fluid and it's good. Any ideas?