Speedometer going crazy

Hey all, discovered a new issue today lol, my speedometer keeps going up even if I'm not accelerating (for instance, I was driving 25mph on base this morning and my speedometer went up to 75!). The fact that it doesn't work doesn't bother me, but I don't want to get a ticket. What are the approximate RPM to speed ratios? I'm used to using my tach to check my speed from my old Saab lol

 

[Hertz]

Sounds like you need a new speedo cable.

1st gear, 4000 rpm 19 MPH
2nd gear, 4000 rpm 32 MPH
3rd gear, 4000 rpm 48 MPH
4th gear, 4000 rpm 65 MPH
5th gear, 4000 rpm 81 MPH

Assuming 24.5 inch tire diameter, stock gear ratios and xfer case, etc.

Go get maxspeed.xls from the Library for variations.

 

awesome! thanks man /ubbthreads/images/graemlins/grin.gif

 

[Barnes]

Hey Hertz, I don't see how that could be caused by the speedo cable. I would suspect it is something to do with the magnetic coupling that is in the speedometer gauge assembly itself.

 

[4thStroke]

Im with barnes on this one. A bad cable will just wobble the needle and make a ticking noise. I dont see how the cable would physically be moving faster.

 

[TRBODSM]

My speedo went out like a month ago and I would be in 1st or 2nd gear and would read 95mph and jump all over the place. I replaced speedo and havnt had a problem since.