no backup lights on 4.3 manual

anyone know where exactly the wiring for the reverse lights on 91 chevy 4.3 go?....about 2yrs ago the reverse lights would flicker when i was backing up....i could control by holding gear shift at certain angle....now they won't come on at all...i need to know what might cause it...i only see 2 electrical connections going to the trans....unplugged and plugged back...they seem ok..is it bad internal switch?....could worn out transmission mounts cause this?....

thanks for any and all help!

wes

there a switch in the tranny tailhousing that resembles a o2 sensor. it takes a deep socket to get out. nearly an inch in size. it was around twenty bucks.