Is this a bad VSS or what?

[JBlack]

The speedometer in my 1996 Explorer Sport is not showing the correct speeds. It says I am going slower than I actually am (GPS verified). It is off by as much as 10mph at an indicated 70mph. Now the entire gauge cluster was replaced in March because the odometer stopped working, but the speedometer still did, but it was off, too (ticket from a state trooper verified ). The transmission was also replaced close to two years ago after I got caught in some flood water. The engine survived but the transmission died. The shop is not sure what year Explorer the used tranny came out of.

Are the gear ratios in the automatic transmissions the same from year-to-year and model-to-model?

What I think is they stuck my original VSS on the "new" tranny and it was damaged in the flood or something... Other than that, my '96 has it's original 3.27 diff and stock rims and tires.

So what I am really wondering, is could I just change out the VSS gear to fix this problem? Also, how many teeth do the original gears have, so I can try and figure out which one to buy, if I can?

Here is a table of my indicated speeds vs. my actual GPS-verified speeds:

Indicated             GPS
20                    20
30                    31
40                    43
50                    55
60                    68
70                    80

I am thinking a gear with 2 less teeth would bring it at least pretty close to normal, right?

Thanks for any help!

 

[IZwack]

http://www.lowpricegears.com/

 

[JBlack]

http://www.lowpricegears.com/

They don't have anything but the 19 tooth in stock... Which from what I can tell is the stock gear, isn't it?

I did some calculations based off the assumption that I do currently have a 19 tooth gear, and if I went with a 17 tooth, I would be ~1.5mph off at an indicated 70, which is good enough for me. Much better than a soild 10mph off...

 

[JBlack]

OK, so I consulted with a friend, and he propsed the idea that my VSS is the one that came with my replacement used tranny, and that the tranny was from an Explorer with a different rear end ratio, and therefor the VSS gear is not the correct one for my Explorer. This makes a lot more sense to me and explains the problem much better.

So, my only question now is this: How many teeth does the original VSS gear have for a 1996 Explorer Sport w/ automatic tranny, a 3.27 rear and P235/75R15 tires?

 

[IZwack]

sorry about that link.. try giving TCI a call:
http://www.tciauto.com/Products/Components/speedometer_gears.asp

 

[Glacier991]

In the stickies at the top is this very helpful thread by Brooklyn Bay:

http://www.explorerforum.com/forums//showthread.php?t=158739

I think your answer lies therein Grasshopper.

 

[JBlack]

Yep, I took mine out and have a tan 19 tooth. I went to my local Ford dealership and ordered a 17 tooth, it should arrive in the morning.

 

[JBlack]

The 17-tooth green gear fixed my problem. My speedo is sooooo much more accurate now.

 

[gijoecam]

Amazing what 2 teeth can do, huh?

-Joe