So i just bought this truck. Its a 97 ford f150 4.6l 4x4. I noticed driving it home that 22mph is actually 25. 31 is really 35 and so on. The truck is all stock except the tires which are 265/75/16. stock size on sticker is 235/70/16. So i went to napa and bought what i believe is a vss its in the transmission with one bolt and has a gear on the end of it. But still didnt solve the prob. I am told there is one in the rear diff on top also but its only a abs sensor? so from here im not sure what to do to fix the speedometer prob and its really bugging me. Also to the symptoms the overdrive does not work it struggles up hill and shifts at high rpm. how can i fix the speedometer problem. i hear there is no tuners for this year truck. thank you.

 

thinking that this is more of a ECM issue ..your truck was setup out of the factory with recommended tire size, in-turn the ECM was programmed for the same.

A good tire shop should be able to help...but also from my understanding a good tuner will be able to adjust for this as well.

If your tranny isn't kicking out of OD on a grade...(it is advisable to take long grades with OD off. Let her Rev. ) does it kick out, or down shift, say if you go to pass another vehicle? if not then you might be wise to get it checked... torque converter lock up isn't releasing.

Or aren't you even able to shift to OD?? even on level ground? what kind of RPMs are you running on relatively flat drive @ 60mph? What kind of gear ratio do you have in the rear end??

 

Doesn't sound like there's a problem at all. It's because of the bigger tires

 

It's not an ECM issue on a 97, that uses a mechanical speedometer. You need a different VSS gear.

 

No tuners will fix the 97-98 speedometers, like glc said you need a vss gear with a different amount of teeth.
http://www.moldyrabbit.com/liquid/speedo_gear.html
Try that and see if it helps, there's another how to on it floating around on here somewhere but that was the first to show up in my google search.

The reason your shifting at higher rpm's is because your tires are bigger than the computer knows so it's trying to rotate them the same amount as the old one's before it shifts, when in reality it doesn't need to because the bigger tire travel's a greater distance in one rotation.

 

The reason why changing the vss gear didn't work is probably because you bought the same one that you already had.

 

ok thank you. now the gear we are talking about and looking at teeth is the grey thing on the end of the vss sensor right? or do i need to find the teeth some place else thanks

 

enriched no even on level ground the od light will not light up or anything. i get no responce from it. i have checked every fuse and all relays nothing is bad. i am at a stump as to why it wont work.

 

The article you have been linked to has all the info you need.

 

ok thank you glc how do i find my gear ratio. i hear there is a bunch of different ones stock on this truck.

 

Count the teeth on the vss gear, they're color coded too iirc. As for axle gear ratio look inside the drivers door jamb find the axle code and then google it.

 

ok the axle code is 19. which i believe means it has the 3.55 gears as what i have found on this forum. here is the link
https://www.f150online.com/forums/ot...code-19-a.html

 

so i pulled the vss out. im not sure which teeth to count. this is my set up 97 ford f150 4.6l 3.55 gears with 265/75/16 tires on it. the gear on the end of the vss is red.

 

No LS, -that's sucks. Huh, didn't know they were color coded.

 

If I had to guess I'd count the teeth on the colored part.