Need some help guys!!! I have a 83 f150 and the other morning I got on the highway and once the speedo it sixty it just dropped over to eighty!!! Got to work and turned the truck off speedo stayed at 55 for about 3 to 4 hours!!! Then again today only this time it happened when I hit 40mph then the needle just dropped over past 80 and was just hanging there on the bottom?? Any ideas? Thanks!!

 

Broken speedometer cable/stripped speedo gears.

 

Am I going to have to get the speedo recalibrated? Or is that only with an electrictronic controled speedo?

 

I'd think inspecting & fixing any mechanical problems with the cable/gears would come first, recalibrate only if necessary would be my route.

 

You never have to get a speedometer re-calibrated unless you go to bigger/smaller tires or go with lower/higher gearing in the differential.

Find out what's broken first. The easy way to do this is to pull the cable and driven gear out of either the transmission or transfer-case (4x4). If the gears have damaged teeth on the cable end, or the gears inside the transmission/transfer-case have damaged teeth, there's your issue. If the teeth on both of those gears (the driven/drive gears) look good, then hook a battery drill up to the cable and spin it to see if your speedometer works right. If it doesn't, then it's the cable or the speedometer gears in the instrument cluster (very unlikely).