when i take off in 1st or 2nd my truck is fine but when i shift into 3rd 4th or 5th the engine revs for a sec like its not hooked to the transmission or something... ... after the half sec rev its lik eit catches and runs like a speedin bullet... ... could this be my clutch, rear end, or what? i thought it could be my clutch slipping but i dont wanna spend the cash til i know... . any in puts appreciated... thanks