Odometer

[monkey44]

Wondering if the odometer captures mileage with a mechanical reader or with something off the GPS?

In older trucks, we had that cable attached to the drive shaft or end gear in the transmission. Today, I'd expect it to be different, but am not sure.

Reason: In the past also, when we up-sized tires from, say a 245 to a 285, the odometer would not read accurately unless you changed the readings.

Just up-sized from 265 tires stock to 285 tires, and want to know how that effects the mileage reading.

Anyone know for sure how the mileage data is collected? Thx M44

BTW: We traveled 7424 miles on 689 gallons - 10.775 MPG with 4000 wet weight camper load ... 2015 Chevy 4x4 w6.0L and 4.10 RE

[wilber1]

Not all manufacturers are the same, some have a pickup at the transmission and some at the axle. My 01 Dodge 2500 had a pickup on the rear axle. You could change a rear end ratio without recalibrating the speedo but you had to if you changed wheel diameter.

[TurnThePage]

On my 97 F150, I changed out a gear at the end of cable that connected to the transmission. That's totally old school. Anything in the last 10 or 15 years will have to be modified digitally on the vehicles computer. Dealers can do it, or you can buy a tuner that can do it.

[2oldman]

Allow me to google that for you.

How stuff works -odometers.

[Bumpyroad]

compare circumference of both which will give you how much you have gained
bumpy

[Triker33]

To find the difference. Check the odometer against 10 miles of mile markers a couple times. In 10 miles it may only register 9.8 now.

I went from 235/80/22.5 to 275/70/22.5 and lost .1 every 10 miles or 1 mile every 100 driven.

[azdryheat]

Not all trucks come with GPS. Doubt they would have two different mechanisms.

[mbopp]

Not sure, but I believe speedo calibration is handled by the drivetrain computer. I think a dealer tech can put in a calibration based on tire size and axle ratio.

[Bionic_Man]

I believe they still go off of some sort of tire rotation. If you changed your tires, in order to be accurate, you will need to have your speedo recalibrated.

Pull out a GPS and check your speed on the highway. I bet it is now off.