Odometer question

[bubbanbrenda]

Ok my hillbilly math is off a little but if you add 406,000 1/8th miles to 344,000 you get 394,750 so I'm close I think.

[Chamberpains]

5280' = 1 mile
5280'/518 rpm = approx.10.1931' distance traveled per revolution
5280'/508 rpm = approx. 10.3937' distance traveled per revolution
Or a difference of approx. .2006' or 2.4072"
Which comes out to approx 103.9366' difference every mile the ECM mistakenly counted.

508 rpm tire is larger than the 518 rpm tire.

So say the ECM has been wrong since mile 1 and its now counted 406,000 miles than the equation would be
406,000 miles x 103.9366 unrecorded feet per mile = 42,198,259.6 feet or approx 7992 miles not accurately recorded.

Now all that math I just showed means absolutely nothing towards what this guy's complaint is unless he actually knew he was losing about 104 feet per recorded mile compared to true traveled mile and cared. This just simply shows that he may not have charged for or reported 7992 miles in the life of the truck. My post is just a collosal waste of time.

Your welcome.

As far as why your odometer is off from the ECM... could be some one changed the instrument cluster or your truck had a brain fart or a bunch of reasons. My odometer once lost about 50,000 miles being towed 350 miles into Denver Colorado. I don't know why.... I usually go with Gremlins. You fed one after dark and thats all. Don't do it again and offset the mileage using Insite to correct your speedo head if it will allow it to change. If not, correct your tire size so your mph (mile per hour) is accurate. And roll on down the road knowing its recording more accurately now.

[snailexpress]

Just my 002 to Chamberpains post - mileage on dash cluster and stored in ECM sometime differs.
Speedometer sometime not accurate comparing with GPS. Good if your real speed is slower then speedometer readings. I have to set 490 rev/ mile to have my speedometer close or slightly over real speed to avoid speed tickets. If I set 508 the real speed is almost 8 miles higher then speedometer readings. Enough for construction zone.
Have no idea why.

[Explosia]

The main reason(s) I wanted this fixed:

1 - My Qualcomm keeps f’ing up and throwing odometer errors, thus causing a chain reaction of other errors, telling me I need to keep paper logs.

2 - In order to log my fuel mileage I have to calculate every stop/route through google maps, which gets frustrating.

3 - Along with complaint 2, I always calculate my rate per mile, (all miles) and I’m relying on my google map figures to do this.

4 - Along with complaints 2 and 3, I have to compile all of my google trip mileage for service intervals, unless I estimate from the faulty odometer.

I changed the rev from 518 to 508. The results are my odometer is now correct. My speedometer has fallen 1 mile an hour and I think my odometer problem is solved. I say I think because I was 23 miles from my destination this morning and my odometer logged 23 miles. Thanks for all the help!

[Chamberpains]

When your tire revolutions are off or you change your gears ratio and the ECM doesn't know it, it causes a linear variance. In this case it would be when you're going say 5 miles an hour the speedometer is reading real close to the correct traveled miles per hour. As you increase your speed say to 30 miles an hour you begin to see a 2 mile an hour or so difference from the true speed travel. As you get up into highway speeds the gap gets even larger which is where you're going to get you're 4 to 8 mile an hour difference from your true rate of speed.

Its important to the speedometer that it knows your correct rear gear ratio, tire size and tailshaft output ratio in the highest gear of the transmission or sometimes how many teeth are on the transmission tailshaft speedo gear so the speed sensor can relay the correct information for the ECM to calculate your rate of speed.

[Explosia]

Before the change my speedometer was about .05-1 mph faster than my actual speed when measured to gps. Now it’s .05-1 less when compared to gps. I will find out more as drive today.