So i finally traded in my old 1990 F250 and bought a 2002 F150 XLT with the triton. It has a 7.5" Fabtech lift sitting on brand new 35's. Is their a way to check if the truck has been regeared with out teraing apart the differential? it runs really smooth and strong. I've put about 700 miles on sense last moday, been driving the hell out of it so i can see if anything is loose or a light pops up before my warranty expires.

Any othere thing i should look out for?
130,000 miles on it.
Looking to buying a programmer so I can adjust the speedometer

Thanks!

 

Id post pics but for some reason i can't anymore.

 

Jack the back end up an inch off the ground and put blocks under the axle so tires are off the ground. Put the transmission in neutral. put a paint mark on the driveshaft so you can see it easy. Rotate one tire one revolution and see how many times the driveshaft rotates.... should be 3.55 or 3.73 unless gear change...... watch the tire on the other side while rotating... it should turn a similar 1 revolution since you have limit slip rear end.

 

where exactly should i jack it up from? Sounds good ill give that a try first thing in the morning and post my results. I've been looking and it seems like something i should have professionally done if need be. Whats the price range for that? I'm in CA where everything seems to be more expensive.

 

they will take a floor jack and set under one side of the axle in the area of the shock mount. jack it up and inch............ with two jacks you could do the other side also and not use stands.. You can do one side if you don't have limit slip, but I thought all ( or most) of the SCrews in those years had that. I have had two and both were 9.75 inch axles with 3.55 limit slip.

 

My girlfriends dad has a 2002 suoer crew with the 5.4 XLT and his has 3.73 gears.
Now the comment above will work IF the truck had stock size tires since it now has 35's this will not work because the larger tire will turn less per driveshaft turn. Id just drop the rear cover and check the gears for the ratio number, with over 100k your due for a fluid change anyways

galaxy S4 using IB AutoGroup

 

your not checking MPH, your checking gear ratios... One tire revolution is 360 degrees no mater what tire is on the truck, or no tire. Your looking for axle rotation vs. drive shaft roation ratio.

 

a 30" tire will spin differently than a 44" tire on the same gear ratio....

galaxy S4 using IB AutoGroup

 

tire diameter has nothing to do with the gear ratio. It has a 3.55 or 3.73 if it is stock gears......... Bigger tire will SLOW DOWN the speedometer and motor RPM for the same ground speed by the ratios of the tires ... 31 inch dia, vs 35 inch diameter... but the GEAR RATIO stays the same.

 

For this check the tire size makes no difference.
If you chalk mark one lug and extend the line straight to the outside of the tire tread, both turn 'one revelation' raised off the ground. So you can see the diameter makes no difference for this check. it's still only one revolution for any diameter.
This is all that needs to be done .
How far the tire travels 'on the road surface' is not<not<not> what is being checked, for 'gear ratio'.</not<not>
Yes, the tire size makes a difference in road speed vs gear ratio but that is not what is being checked for. Only the gear ratio, not the final drive distance on the road.
Big difference.
Good luck.

 

For a gear ratio check tire size makes no difference. You're just looking for how many revolutions of the driveshaft equal one revolution of the axle. The tire can be 12' tall...it still makes one revolution every time the axle makes one. Remember as a kid putting little cars on a 33 1/3 record?....Who won? ( yes I'm old)