Is my speedometer still off...?
 

Hey guys,

Quick question, I upgraded my '01 XL from the stock tires (27 inch I think) and 3.73 gearing to 31's and 4.10's with L/S.

Now my question is, before I swapped in the new gearing I was getting a MPG of about 18, and when I adjusted that for tire size, over 20. But yesterday after running a full tank with the new gear, my MPG was still only about 18.5. According to my math, with 31's and 4.10's I should be right back to the stock ratio and I shouldn't have to recalibrate my speedometer in order to have accurate numbers.

So is my speedometer still off and do I need to go visit the dealer to get it adjusted, or did my MPG just take a hit from going to 4.10's?

My driving routine has been relatively the same, about 80% highway and 20% city.

Re: Is my speedometer still off...?
 

In my 05 I had stock size tires with 3.55 gears. I then put on 31" tires and it was off by about 6 and my MPG sucked.

I put in a 4.10 L/S and my speedometer is correct again and my MPG was back where it was before.

Never had a dealer do anything.

Re: Is my speedometer still off...?
 

do you have a gps or know someone that does?

Re: Is my speedometer still off...?
 

I wish I did, we have one at home, but it doesn't have the speedometer on it.

STL, that's what I figured because it's supposed to be back to stock speed because with 31's and 4.10's it should be near the stock gear ratio.

My only question though is if your truck came with 3.55's stock and the stock 27's then going to 4.10's would give you a higher final drive ratio then what you had stock...so maybe mine is still off?

Re: Is my speedometer still off...?
 

My stock tires were bigger then your stock tires.

I had 235/75/16 on mine originally which is a 29"