I just picked up a used 1997 4x4 supercab XLT three weeks ago for what I thought was a great price. Then I discovered that the back seats weren't wet due to the detail guys doing a crappy job shampooing the seats and carpet, but because I have the leaking rear window problem. Thanks to finding this board I knew where to look, unfortunately there is no warranty, so I am having the window replaced today at my expense for $335.

Now I believe that the speedomoter is off by about 10%! I have done the drive at a steady speed for a few miles thing get the average and divide into 3600 and when I think I am going 60MPH, based on this I am going 66MPH and when I thought I was going 65MPH I am actually going around 74MPH!

The truck is a 4.6L with 3:55 rear end based on the door sticker. It has 265/75R16 tires. What are the stock tires for a 97 F150? I assume these are replacement tires since they are Coopers. If stock is say 255/70R16, could switching to the existing tires throw off the speedometer that much? Could the odometer also be affected by this as well? It read only 67K miles when I bought it, so should I think that there are probably more miles on the truck?

Sorry for the long post. Great website, I have learned lots. So far no door cracks (knocking on wood)!

Rob

 

The door jamb sticker should also say what size tires are spec'd. Mine said 255/70/16, BUT it actually had 235/70/16's on it. I'm pretty sure they were the original tires (BFG Long Trails) because the spare was the exact same tire and still brand new. The truck had 61k on it when I bought it.

I put 255/70/16's on it and did not notice any difference in speedo and odometer readings. Actually, didn't really check and I only had them for a month before deciding I wanted taller tires. I then got some 265/75/16's. This is where I really noticed a difference in the speedo. Mine was only off by 5%. I would pass by 2 mile marker posts, but the odometer would say I only went 1.9 miles. I lost 1/10th mile every two miles traveled, or one mile every twenty actual miles (my odo would say I only went 19 miles).

So, depending on how many miles the taller tires have been on the truck, your odo will show fewer miles then it actually has.

I just had to change the VSS gear to one with one fewer teeth on it. (stock was a 20 tooth, so I put in a 19 tooth one (5.4, 4x4, 3.55 gears)). Brought it back to near perfect. Now I'm only 1/10 mile off after 8 mile posts, or one mile every 80 miles. I can live with that.

 

Thanks for the reply Mitch! I'll be watching the odometer a little closer today when I pick it up from the glass shop. The rain we're having should be a good test for the new slider!

Not being a real car guy, what the heck is the VSS and where do I find it? I called Tacoma Speedometer and they gave me a quote of $20 to check the speedometer and $46 for parts and labor to re-calibrate it.

Thanks again,
Rob

 

Vehicle
Speed
Sensor

When you pull it out of the trans (not sure of location), it has a removable gear that can be replace with a gear with a different tooth count.

There is a speedo check on the bottom of www.therangerstation.com

 

Just noticed you're from WA too. Had to look up Littlerock however! Kinda out there all by yourself, huh? Makes me glad I don't have the slider window. No leaks, but got the optional "door crack" feature.

VSS is the Vehicle Speed Sensor and it's located on the rear of the tranny. It's a small plastic gear that sends your speed to the computer so it knows when to shift and tells your speedo and odo what to do. No actual cable that turns in these rigs. Since you have a 97 that's all that needs to be changed. It's pretty easy to do if you have turned a wrench on a car before, but if you don't feel comfortable that, I'd let someone else do it.

That speedo shop is charging a pretty high price to do the work. I bought my gear from a Ford dealer for $12 and took all of 5 minutes to swap it out.

The only thing I'm not positive on is what tranny you have. I'm only familar with the auto. I have the 5.4 and the 4R100 tranny. The other auto tranny is a 4R70, and I don't know if they share the same VSS gears. Probably, but not positive. If you have the 5 speed, then I have no clue as to what it uses. Again, maybe the same one. Dunno.

Good luck, and check around for other prices on swapping out that gear. But that maybe the only shop in Littlerock, so they can and do charge whatever they want.

If you're in the Puyallup/Tacoma area, I'd be willing to meet up with ya and help you out!