The PO installed very large tires on my Ram. The are still 15" but way higher. The speedometer is totally crazy. 42 mph appears to be 60 mph.
Is this set gear driven and are there different gears I can put in to change it?
215 70 15 up to 235 75 15 Goodyear Wranglers.
Thanks

 

You stepped up from a 27" tall tire to a 29" tall tire. Not a big step.
The speedometer can be easily adjusted for that. But a 17mph difference doesn't seem right.
I'm not sure if yours still uses the gear in the transmission but if so they were color coded. Just need to get a gear for your transmission with your new tire size and diff gear ratio.
A 235/75R15 is a stock tire size. Nothing special.
The 215/70R15 must have looked funny small on a full size truck.

 

I'm curious about this too as I went up to 33's and my speedo is off. I have learned to live with it, but would like to fix it if its easy. I know on mechanical speedos there is a gear in the tcase that is realativly easy to change, but im not sure about an electric speedo.

 

Actually they look pretty good. Don't look stupid oversize at all. I am used to stock size on my 79 Palomino so each time I climb in I am running into something. usually with my shin or head.

 

Electronic speedos can be easily reprogrammed at the dealership.

I stepped from 215/70R15 (27") to 33X12.5X15 and was able to correct my speedometer with my Superchip programmer.

 

I didn't think that a 1991 speedo was programmable. Its electric, but there are wires running to a connector in the tcase. I thought there was still a gear in the tcase that controls the speedo.

 

Your speedo is way off. If you were actually traveling 60 miles per hour, your speedometer should have to read about 56 miles per hour with the new bigger tire size. Likewise, a reading of 60 should indicate an actual speed of about 65. It sounds like somebody may have changed the gear ratio as well.