Speedometer reading incorrect speed
 

I have a 1993 Cummins 4x4 with the 5 speed manual tranny. It's always seem like I was going a lot faster than what the speedo is reading so I verified it with my GPS. I'm about 15 mph off when the speedometer reads 50 (gps says I'm going 65). I'm running 265/85/R16 tires. Is there any way to fix this?

Thanks

you need a new spedo gear ratio box I have them for sale custom built to order there about a hundred bucks shipped to you so how important is it for the spedo to read correctly? :humm: