Aggievet03

Are you referring to a small gear in the instrument cluster that drives both the speedo and odo?

I just picked up a 1990 LS 400 in pretty good shape, but the speedometer is dead. The needle is buried way below zero and never moves. The primary mechanical odometer also does not move. Oddly, however, the two digital trip odometers work just fine and cruise control works perfectly. Is this likely an instrument cluster issue or a speed sensor? something else? What's the simplest way to diagnose this? Thanks in advance for any insight. -Matt