changing vss gear

93xplorersport said:

http://www.summitracing.com/parts/SDA-75C4OZ17271A/Application/?prefilter=1. Is this the right gear for 35 and 4.56 gears with the drive gear bein 8 tooth and the tires actually measuring 34.76 inches?

Click to expand...

what vss gear do you currently have?

The speedometer gears on the VSS for these trucks have been the same as those used 40 years ago. I had to replace mine and the part number was from the 1960's. A "knowledgable" Ford counter person should be able to find the right one for you. When I was still working at the dealer, you needed to know how far off the speedo was, and how many teeth were on the gear you had. 1 tooth will change the speedo about 3-5 mph. If you are travelling faster than what your speedo reads, you need to subtract the appropriate number teeth. If you are travelling slower than what your speedo reads, then add teeth.
I had to go from a yellow gear to a black one-which subtracted teeth.

I haven't actually pulled my vss out and checked but I did the math problem 8x3.27x697.87/1000=18.25 teeth. That was done with my stock tire height of 28.9, now if I do the same equation with my 31s that actually measure 30.75 I get 17.15 teeth.

Now from what I have read that is correct that I should lose a tooth for every 3 to 5 mph difference in speedo and actual speed. But if you change your gear you have to use the new ratio to make it accurate.

Have I miss read somethin or am I on the right track

93xplorersport said:

I haven't actually pulled my vss out and checked but I did the math problem 8x3.27x697.87/1000=18.25 teeth. That was done with my stock tire height of 28.9, now if I do the same equation with my 31s that actually measure 30.75 I get 17.15 teeth.

Now from what I have read that is correct that I should lose a tooth for every 3 to 5 mph difference in speedo and actual speed. But if you change your gear you have to use the new ratio to make it accurate.

Have I miss read somethin or am I on the right track

Click to expand...

it literally takes less than 5 minutes to take it off count gears and put back in. idk anything about the math stuff you did.

if you put a automatic speed sensor gear in a 4wd what will happen? i will need a 19 or 20 tooth gear but i can only find them for autos. i used this website to do my math http://accutach.com/FordMustangVSSCalculator.aspx my tire revs per mile for the 33 i want are 616.10 and for the 35 are 580.22 and the drive gear is 7 tooth. hope this helps

The speedo gear for the manual/4x4 is a different shape than the one for an auto trans. You can't interchange them.

~Mark

i have done some diggin and i have found this website hopefully it helps someone else http://www.transmissioncenter.net/speedometer_calibration_______va.htm

93xplorersport said:

i have done some diggin and i have found this website hopefully it helps someone else http://www.transmissioncenter.net/speedometer_calibration_______va.htm

Click to expand...

I've bought from PATC before, no issues.. (was a few years ago).

~Mark