Hey guys,


I recently put my stock 18's back on from the factory 20's and removed a couple of other things. Now my speedo is wacked. At 75 on GPS my speedo says I'm going 89mph because I switched the rear end to a 4.10 from a 3.55

Is my odometer messed up now because of the changes? The best I avg. with the 20's was about 15.8mpg and that was highway driving. I just did my first tank back on 18's and stock tune and I avg. 18.2 Now how can that be? The 20's can't take that much mpg away can they? I'm thinking it's reading my mph wrong so it's screwing up my mpg.

Thoughts?

 

I believe my truck racked up the miles faster when my speedo read ~5 mph over due to my EDGE (and the way I programmed it).

 

Yes I believe the mileage will be off. When you change tire size the mileage and the speedo are off from what I have read

 

Yes

 

I had the same problem. What tuner do you have? With the SCT X Cal 2, you can make speedometer corrections for tires and gears.

 

****! I'm not running a tuner at the moment and that's why it so off. I changed the gear ratios so it's wack. I need to get that fixed asap because it's racking up the miles then. lol Says I'm doing like 95 when I'm going 80.

That clears up my fuel mileage question then. I was like how the hell can I get 18.25 from what I had before??? lol

 

I went from 3.55's to 4.10's and I never updated my ECU.

I have it set in my ScanGauge as to what the correct MPH is.. so what I did was I just got up to 55 according to my SG and I noted the new mph on my cluster... its like when I go a true 55 mph, I'm really doing 60 on the instrument cluster.

As far as extra miles being added.. I'm not planning on selling the truck, it's mine forever until I send it to the crushers... which will be a very longggg time.

 

nobody really answered the question!!

 

Actually... it can be done... but needs to be a joint effort.

So here's the easy way:

Someone on here do 55 mph (who has 3.55's) for 1 mile, and get a stopwatch and measure the time it takes for the truck to complete 1 mile on the odo.

You measure the time doing 55 mph (with your 4.10's) for 1 mile, and get a stopwatch and measure the time it takes for the truck to complete 1 mile on your odo.

(BTW: I'd give you mine... but I've got the 5 speed, and the final output is smaller than the automatic.)

Post both of your results.

It will then tell you. FYI you need a stopwatch... one with 100ths of seconds.

 

Read post 4, he clearly gave the answer.

 

The way the odo and speedo work is there is a little magnet on one gear in the tranny everytime it goes all the way around its part of a mile. So after x number of rotations the computers read it as 1 mile. Dependant on how many in a given time gives speed.

The tuners just set the computer differently.