Hi Y'all, I just joined the group as I've picked up a 97 ram van 2500 conversion (mild) with a V6 and an auto trans. The speedometer always says that I'm going about 10 percent faster than I really am, and the odometer is also off, showing that I've traveled about 10 percent further than I have. I havn't had a chance to pick up a book yet, the van had bashed in rear doors when I bought it and I've been concentrating on fixing those. Anyhow, can someone tell me whether or not I can change the pinion to the speedometer cable, and, does it even have a cable? Thanks in advance, Tracka96

 

No cable, there is a speed sensor on the rear differential that is used for the speedometer. Check you tire sizes and make sure they're what is called for on the van. A smaller tire will give you a higher reading on the speedometer.

 

Thanks! It looks like you got it. The tires are 225/75 and should be 235/75, it seems like that must be what my problem is. Thanks again, Tracka96

 

If you want to see the difference between the two tire sizes for yourself, enter the tire sizes in this calculator. The 235/75R15 first and the 225/75R15 second, then click the compare button.
http://www.discounttiredirect.com/di...foTireMath.jsp

 

Alloro, Thanks for that link, it works out about right for my odometer, but I'm pretty sure my speedometer is off by more than that, I believe by about 10 percent. I'll get my wife to drive her car at a steady 60 MPH and follow her with the van, and see what it says. Tracka96

 

Who says the car's speedometer isn't off a bit? To check mine I usually look for those radar signs the police like to put on the side of the road every now and then. Occasionally, I have also stopped and asked a local PD officer that was shooting radar if he would allow me to drive past him at a steady speed and have him note my speed on his gun. I've never had one say no.

 

highway mile markers

at true 60 mph
1 mile a minute
do math

 

my 94 ram van is a mark 3 version and the speedo/odo does not work at all. is there really a sensor on the rear differential? thanks for the info. i will look. i am an old mopar man and have not had knoledge of this newer electronic world. pulled the unit off my working 93 cargo van and still have no speedometer/odo. is there a fuse that may be blown? i even changed the cluster to see if that helped. no. ??

 

I think you can answer that question better than any of us. Just take a look under there and see if you see a sensor on top of the differential.

 

If you have a GPS navigation unit there should be a MPH/KPH readout on the screen. Once the GPS syncs up with the tracking satellites your screen readout will be perfectly accurate as you travel down the road.