hey guys

just need some help
was wondering if anyone knows weateher or not there is a plug or something inside the engine that controls the speedometer- im having a problem with the speedometer not working, i swaped a speedometer with my 90 maxima into my 91 and it still doesnt work, so i figure it might not b the guages , but it may b a plug from inside the engine that is acting funny? any solutions? HELP