1991 Mustang GT speedometer

i have a 91 5.0. the only thing really done to it is headers and flowmaster exhaust. also the rear has an extra clutch in it. the speedometer has been bouncing around lately (common for fox bodies) but now once i start moving it jumps up to 80 and stays there until i get over 80 and then it seems to be accurate. i think that it is the cable. does anybody know for sure?

Probably stripped the speedo gear. Plastic gear in the tranny that the speedo reads from often stripped from simply driving to fast. Have you gone faster than the speedo is calibrated for recently?

Could be a stripped speedo gear in the tranny also semi common is the speedo itself is broke and you need to replace it.

i looked at the speedo gear and it isnt stripped. in fact it is almost brand new. if it is the speedometer how do i check it and how easy is it to replace if i find out that is what it is. do i have to replace the whole cluster?

i looked at the speedo gear and it isnt stripped. in fact it is almost brand new. if it is the speedometer how do i check it and how easy is it to replace if i find out that is what it is. do i have to replace the whole cluster?

Take the speedo out and spin where the speedo cable goes in by hand different amounts. If it just keeps bouncing straight to 80mph no matter how you spin it it's broke. No you can replace just the speedo.