speedo gearing help

[madbiker4]

My truck reads 10 mph slow up to about 45 then the faster I go the more off it gets. I know it has the wrong drive gear for the 3.00 gearing in the rearend. my question is will I be ok using any size cable drive gear in order to get the proper speedo reading or do I have to change the gear on the tail shaft to match the cable gear? I see a wide range of cable drive gears available, but only 2 different size tail shaft gears. will any cable drive gear mesh properly with either tail shaft gear?

thanks, -Madbiker4

[fordman]

at the bottom of this list is a chart for each transmission. see what the charts say. http://www.fordification.com/partnos/partnos-index.htm

[madbiker4]

Thanks. according to this chart I will need a 16 or 17 tooth gear depending on how many teeth are on the drive ( not sure if PO used thrans from van or if he used original truck trans ) I currently have a 21 tooth cable gear in it! even if it's not exact it would be nice to be within a few MPH of actual speed. would also be nice to be able to have the mile meter work for milage/mpg checks. thanks a bunch fordman!

[Bullitt390]

Doesn't matter what the transmission gear is...

If you read 35 when you do 45 then the speedo is off 23%

If you have a 21 tooth gear, you need to speed it up 23%, so the gear needs to be smaller, therefore, that equals 4.83 teeth or...

a gear with 16.17 teeth... suppose 16 will suffice then.

Josh

[madbiker4]

Thanks, I'll have to order one then. I may also get the 17 tooth just in case thought. no point in paying $10 for shipping twice on a $6 item.

[Bullitt390]

I would just go to the junkyard and scrounge up a handfull for $2

Josh

[fmartin_gila1]

Ford Dealers still carry the gears also.

Fred

[ForingaMex]

Ford Dealers still carry the gears also.

Fred

Not in stock around here anyway. It's a special order and they come in packages of two.