You need a VSS gear with one less tooth.

 

Which one do I have now. I counted and not sure if its 19 or 20 or 18. Its the red colored one

 

Wait how are you not sure how many teeth it has?

 

uhhhhh...

 

Just place a mark on it, and count till you get back to that same mark.

 

Ok guys so here is an update. I talked to the ford dealer this morning. The red colored one that is in my truck is the 21 tooth gear. So it has 265/75/16 with 3.55 gear and 21 vss. So should I go down to the 20 tooth or the 19 tooth. Thanks for all your help guys

 

Go to a 20.

 

ok i got the 20 tooth. it seems like it fixed it a lil but im still 1 to 3 mph off. would going to a 19 tooth fix that

 

Maybe, it's gonna be close whether it fixes it or put's you under. Does 1 to 3 really bother you that much? Mine's like 20 off and I can still drive the speed limit fine.

 

My truck had a 20 tooth gear stock (black gear) with 3.55 gears. The stock tire size was 255/70/16.

I went to 265/75/16 and I had the same issues with the shifting and the speedo/odo being way off..

I got a 19 tooth gear (pink, I think it was... ) This was 10 years ago, so I don't remember for sure..

It's still about 1-2 mph slow, but it's close enough and it shifts like it did before.

Not sure about your OD light/button?? I've heard that the wire for it in the lever or the column can get cut sometimes??

Good luck!

Mitch