5th & reverse switch, HELP!
 

i replaced the " 5th gear & reverse light switch" in my '87 s4. the switch works but i messed up somewhere. now my back-up lights come on when i'm in 5th and reverse. i can't figure out weither the wires are reversed (there are only two wire leads to hook up), or if i need to put a shim in between the switch and the tranny. any help would be great!