Engine/Transmission (1998.5 - 2002) 1998.5 speedomter

[SAndreasen]

Is there a way to change the speedometer for bigger tires or am I stuck with it being off for the rest of my life ?
Thanks Shaun

 

[cerberusiam]

You have to reprogram the ECM with the correct tire size. The rotation is pulled from the ABS sensor then uses a conversion factor to convert to mph. You need a Smarty.

 

[RonaldLarson]

Fake it! Measure the difference between old and new. Divide the sum by the larger diameter. That gives you the percentage of error. IUse that percentage to fudge the readings. verify with a GPS. For instance, 245 to 265 Michellins equals 9.9 percent up, on the odo, and 4 MPH on the speeedo, verified by GPS.

 

[SAndreasen]

Thanks for the reply its off about 5 mph so how do I figure out how much its throwing my trip meter off

 

[cerberusiam]

You can't use a single mph reading to find the percentage difference, the amount off will vary with speed. Buy a Smarty and quit guessing. :-laf

Find a road you know for sure the measured miles are correct and run it for 5 miles and calculate a difference between actual and measured. That will get you close for actual percentage discrepency. Still will be off because 1/10 miles is not fine enough to really define the calculation.

 

[SAndreasen]

I know its five at 6o and only about 2 at 35 . I'd like a smarty but called today and they are 650 I don't want to spend that much for a programmer

 

[cerberusiam]

Yeah, that is typical and percentage runs from 6% to 9% off as the differences at those speeds. Using the odo on a measured mile will get you closer for the total miles but the factor doesn't geenrally work on the speedo, not fine enough measurement.

Well, Smarty $650, DRBIII or Equivalent $2500. The Smarty is still a buy as it reads and clears codes, adjust TQ management, add power, etc. The other choice is a dealer or shop with SnapOn scanner that can set the pinion factor. Depends on what you want to spend and do.

Diesel trucks = not cheap!

 

[SAndreasen]

What I really want is just to recalibrate the speedometer but I've called three dealers and two diesel shops and they act like Im looking for muffler bearings for an Essex tri directional

 

[cerberusiam]

LOL, I swear the dealers are getting to be about totally worthless for anything other new vehicles. All they have to do is hook up their scanner and set the pinion factor to the revs per mile for your tire and it will be corrected.

You are a bit away from any good dealers unless you want to drive to Dave Smith Motors. I assume you found out Larry Miller is totally useless. Mountain Home Auto Ranch used to have a decent tech but who knows now and that is trip also.

 

[mfurrh55]

Buy a garmin and run off gps, a whole lot cheaper in the long run

 

[SAndreasen]

I called the dealers close buy and even checked the ford dealers hoping somebody was smart enough to hook the scanner up and change jt but they can't I had a hyper tech and all I had to do was type in the tire in inches and that was it

 

[mfurrh55]

I called the dealers close buy and even checked the ford dealers hoping somebody was smart enough to hook the scanner up and change jt but they can't I had a hyper tech and all I had to do was type in the tire in inches and that was it

Sounds like you solved your problem, Great

 

[SAndreasen]

I haven't got the hypertec anymore I wish I did

 

[JR]

Google TS Performance respeed, it calibrates the ABS like the Smarty does, but that is all it can do. It is a third of the cost of the Smarty but still very pricey considering its capabilities. I for one can tell you the Smarty is waaay funner....

 

[Road Dog]

Yeah, that is typical and percentage runs from 6% to 9% off as the differences at those speeds. Using the odo on a measured mile will get you closer for the total miles but the factor doesn't geenrally work on the speedo, not fine enough measurement.

I don't understand. The ABS sensor is counting pulses from a tone ring on the diff ring. That translates into axle revolutions and you use a Chrysler scan tool (or almost any aftermarket programmer) to set the revolutions per mile (or tire size) . Tire specs include the rev/mile these days. The tire revolutions/mile will change slightly based on tire wear, load (effective radius), temperature & pressure.