gear change, spedo change

[DGoyer]

I recently changed to 373's from 410's truck was just too low. I called my local dealer to ask about flashing the spedo. They had no clue. has anyone done this?

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2003 3500 2w 6 speed laramie quad new 3:73

 

[p-Bar]

I think the sensor works off the ring gear. So it wouldn't matter. How do you feel about the change you did?

 

[MCummings]

The speedo only measure axle speed in reality.



Tire size change, recalibrate speedo. Transmission, gear, or transfer case change... No calibration required...



Merrick

 

[DGoyer]

I took the truck on a 400 mile trip empty, quieter in cab at 70, still don't use
1st

 

[SAlex]

The speedo only measure axle speed in reality.



Tire size change, recalibrate speedo. Transmission, gear, or transfer case change... No calibration required...



Merrick

Really? I went from 3. 73's to 4. 56's and now my speedo is off nearly 11 mph! I have tested it with gps. great for sled pull, ran a 12. 1 in the qtr mile with 37 inch tires, but freeway may-be too low! steve

 

[DGoyer]

Looks like you also changed tire size. that will fool ring senser

 

[Ram Rod]

I am running 37's . I took my truck to a dealer, they put it on jack stands, put the truck in gear and calibrated the speedo. It is right on and it cost me $60. 00 . No idea how they did it.

 

[MCummings]

If your truck is a '98 and newer (to current), the speed signal is picked up off a RWSS (Rear Wheel Speed Sensor), and that sensor measures the speed of rotation of the ring gear. If you have a '97 or older, the speed signal is picked up at the rear of the trans, and any changes in the driveline will effect your speedo.





On '98's+ gear changes do not affect speedometer readings. The Pinion spins faster, but not the ring gear when you gear down... To travel the smae speed before the gear down was done, the axle had to spin XX times a mile. It does the same XX rotations now, but the Pinion now spins more times in that same period... That's what gives you more mechanical advantage, and that will either, require less power to move a load, or simulate more power at the track...





Merrick