i got my ford c4 transmission rebuilt with a shift kit 5 months ago, i have it in properly mounted to a ford 289 v8 and the right amount of F-type fluid in it, ive checked the linkage and it seems to be hooked up fine, for some reason just the other day when i put it in reverse and gave it gas the car didnt move at ALL! all my other gears work except the reverse, please help! any suggestions before i take it to a mechanic and use up my money