I have been trying to find a speedometer drive gear because mine is bad, and found it quite hard, I did this speedometer calibration program and entered all the correct information and this is my answer:

Bowling's Speedometer Calibration Program


Input Parameters Are the Following:

• <CODE>Speedometer Revolutions/mile = 657</CODE>
• <CODE>Rear Tire Diameter (Inches) = 31.70</CODE>
• <CODE>Differential Gear Ratio = 4.10</CODE>
• <CODE>Driven Gear Teeth Number = 20</CODE>

Computation Results:

<CODE>Computed Drive Gear is 5 </CODE>
<CODE>Ratio of Driven Over Drive Gear is 4.0</CODE>
<CODE></CODE>
<CODE></CODE>
<CODE>What does it mean I need???</CODE>

 

Is this for the truck in your signature (C6)?
If so, the DRIVE gear is part of the tailshaft and can't be changed. The DRIVEN gear is the one that's on the end of the speedometer cable and can be changed.
The info needed to identify the correct driven gear is trans. model, rear gear ratio, tire size (not diameter), and 2WD/4WD.

 

I THINK THAT JEFFS BRONCO GRAVEYARD HAS A CHART FOR THIS MAYBE THIS WILL HELP

 

C6

Speedometer DRIVE gear: Made as part of the output shaft, so it is not available by itself.

Speedometer DRIVEN gear: At the end of the cable. 16-21 teeth available.

 

the drive gear should be able to be changed (it is in the 205 transfer case and not exactly in the C6 trans), me and my dad changed his in his np435 with borg warner transfer case???

 

There is no Ford part number for a C6 speedometer DRIVE gear simply because there isn't one. 2WD or 4WD makes no difference!

EVERY 1966/97 C6 has the DRIVE gear made as part of the output shaft.

There are DRIVE gears for manual transmissions (NP435, T-18, T-19 and etc), but not for a C6.

 

well mine is bad which makes my speedometer not work, so what can I do about a non working speedometer?

 

Bill, I think the part BiltFordTuff is looking for is basic p/n 17285. But I'm getting lost trying to find the actual p/n for him.
He has an NP205 transfer case and, according to his original post, he needs a five tooth gear.
But, like I said, other than that I'm lost.
Here is the illustration that shows the gear.
Click on the .pdf link to view.

 

are you saying it is possible to change this gear or would I have to change the entire output shaft??? And would a gear or output shaft work in my 250 4wd (C6 Np205) if it came out of a 150 4wd (C6 Np205)???

 

I'm no 4WD expert by any stretch of the imagination but going by the illustration from the parts catalog the gear is separate from the shaft and can be replaced. As far as interchangeability between F150 & 250 I'll let someone who is more knowledgeable on the subject chime in.

 

Not to be a nuisance to anyone but I just took my drive gear out pretty easy so just letting you know, you can replace the drive gears

 

so would any one know what color gear to use with bigger tires? as i know my speedo is running slower than road speed i have 350 gears,c6 auto 35x 12.50x15 tires [stock is 235x15] a big difference in size any one figure this out for this size?