hey guys brand new to the board , and pretty new to trucks . i just had 4.10's instaled in my 03 2wd crew and it drives and shifts just like be for . i checked the speedo agenst my gps unit and when the truck indacates 60 the gps says 52 . from the reading i have done , i thought there was a speed sensor on the axel that measures the truck's speed . i have the stock tires 255-70-16 , my mfg date is 04 / 03 . a dealership told me there were some changes made early in production on the 03's with the prossesors could i have a 02 speck truck and if so what would be the best way to fix the speedo error ? i also plan on doing a cold air intake , and a chip . my mods to date are 3'' cat back exhaust and 4.10 gears . can a custom chip fix the speedo ? any sugestions / help would be great thanks .

 

Sounds like you got yourself into something without doing all your homework!

No worries, you've come to the right place..

You're truck will drive and shift like it did before, you haven't really done anything other than to change the gears. It should accelerate quicker but, you're speed is now physically lower since you haven't put bigger tires on to compensate. The speed sensor takes readings off the driveshaft, not the ground. So, the driveshaft is still spinning the same rate when the speedo is doing 60, but the axle is spinning slower because of the gear change and therefore reducing your actual speed. Does that make sense?

edit - To clarify, your tire is still covering the same distance in one rotation but your axle is now rotating at the driveshaft 4.10 times for every single rotation of the tire. Before, the driveshaft would rotate 3.xx times to cover the same distance/rotation of the tire.

To fix the speedo, get a tuner and re-adjust or as you mentioned, a custom chip. Since you are using a GPS also, this will really help you fine tune. Based on what you have done, you have actually reduced the tire size as far as the speedo is concerned.

Just why did you go to 4.10's anyways? You didn't put larger tires on, which is the main reason people change gear ratios.. Sounds like you changed over from around the 3.90's..

Please post up some more, we're here to help!

 

i had 3.55's and i changed the gears out for better towing and pepper exceleration . i dont plan on going with any bigger tires . i thought the speed sensor was on the axel not the drive shaft . it's not in the tail shaft of the transmition , like in older rwd fords is it ? i thing i forgot to mention that the truck is a 2wd and a 4.6 and being a crewcab it is kind of heavy . some times i pull a flat bed trailer with a 2500 lb kabota tractor on it , or the sport bikes to the track . last summer i took three sport bikes to canada , about a 1200 mi round trip and it realy doggs on the hills . again any help would be great thanks .

 

any one

 

oops

 

i would get a tuner or chip with a custom tunning you wont be sorrie and you can fix the gear change i want to do the same thing also to my screw

 

I agree...get an X Cal 2 from Troyer Performance with custom tunes...it will be able to correct your speedometer and the custom tow tunes will help you with your towing...

 

Seriously, this thread is 3 years old. Either the OP gave up or found his solution.

Any dealer can reprogram the axle ratio as long as is a possible stock size. Same with tires.

 

thats prolly why houlster said oops....
nice eye, i didnt catch it the first time i read it