Speedometer calibration for 37's

[iroc89al3]

Hi all, dont really post on here alot but lurke around almost everyday. I seen a few members who squeezed 37's on the stock 20" rims and loved it. $1900 later and I finally have "that truck". Honestly the compliments are amazing. It really seems like im driving a $200k Italian sports car, everywhere I go people love my truck! (not being ****y in any way just very proud). Any who, ive had the tires for about 2k miles now and still have not done any modificatons for the bigger tires.

I went on the major highway and watched the markers and the mileage of my tuck is only like 20 feet less then .1 off of the mile markers (if that makes any sense). So i figured that was pretty good, obviously not correct but good enough to hold me out where i could spend a few more hundred on a programer. This was about a month ago. Today went past one of those " speed limit 35- your speed ..." signs and it was almost 6 miles off of what the seedo read!

Heres the kicker= truck is the 5.4 triton(dont ban me!) I have found a sh*t-ton of info/programers/calibrators for the 6.4, and none for the 5.4. The popular ones that would work for the 5.4 (hypertech, superchips etc.) only go up to 35" tires. Theses arent something that can be returned so I dont want to take a chance and buy them to find out they wont work.

Im hoping someone on here possibly has a 5.4 with some info or knows a buddy that was in the same boat as me and has an answer.

Thanks in advanced for any info and again hope i dont get flammed for the gasser, because this is an AMAZING website even for the young guys like me who couldnt afford the $8k+ sticker price of the diesel engine on top of the purchase of there first brand new automobile. Al III

P.s also how much extra miles do you think i put on the truck if judging by the odometer i went approx 2500 miles with the new tires?

[wired1]

Wow i didn't know they still put the 5.4 in these trucks, i thought it was the diesel or v10. But you might want to look at a hypertech programer or maybe a superlift truespeed seeing how you got a gaser.

[iroc89al3]

hmm didnt know superlift made a product like that gotta look into that thx.. Also to add to the post the truck is a 2008 f350 all stock except for leveling kit and 37's. thx al

[Jonnydime]

Putting the larger tires on will make your odometer read slow not fast. So with the bigger tires your a putting less miles on your truck.

[dazdillenger]

find someone with autoenginuity to reprogram your speedo, or take it to the dealer! They can calibrate the speedo for up to a 40" tire!

[Idahoser]

Originally Posted by Jonnydime

Putting the larger tires on will make your odometer read slow not fast. So with the bigger tires your a putting less miles on your truck.

... maybe I'm confused but I think your odometer is showing fewer miles than you are actually traveling?

It measures ROTATIONs, and one rotation is putting you farther down the road than it was.

[dazdillenger]

Larger tires will make the speedometer read slower than you are going. Thus, you will have traveled farther than your odometer states. By keeping the speedometer incorrect, you are keeping your mileage LOWER than it should be.

[iroc89al3]

hmm so maybe this is a GOOD thing? lol... well what about abs and fuel mileage? would you suggest not even making any changes? is there any downfall for not calibrating it? Im pretty sure its due to the size of the tires, but the braking is HORRIBLE! The poor dog i hit over the summer can justify that one

[srjd]

i wouldn't worry about it. It doesn't bother me just get use to it so you know how fast your going and don't get tickets....i just look at it like its my extended warranty program

[dazdillenger]

I didn't realize what a big deal it was until I corrected it My ABS works sooo much better, transmission shifts more reliably, and it's so much more professional.