What speedometer gear size & part number do I need for 17" wheels
Also are any metal or are all plastic gears

 

We're gonna need a little more info to help you. Need to know tire size and rear axle ratio. Just because you changed to 17" wheels, doesn't mean you have to change your speedometer gear. If your tire size is close to stock diameter, it should be fine. To my knowledge, all the gears are plastic. Is there a reason you want a metal gear? Did yours fail? If so, you might need a new cable, or your cable might be routed wrong. Can't have any sharp bends . If you google ford speedometer gear chart, there are several results with part numbers that can tell you what you need to know.

 

I just bought a 4 pack from Pony Parts and was going to work my way through them until I found one pretty close. Ended up the first one I tried did the trick (:

 

Thanx , Currently have a 225/65/17 Tiger Paw made out of rubber
Speedometer cable got destroyed by the headers , my fault........I thought a metal gear might last longer than a plastic gear

 

Unless there is a bind some place, plastic gears will last a long time. That's what Ford stuck in them when they were built. Don't recall seeing a metal one, but guess they are out there. The ones I just got from the Pony store appeared to be 3-d printed plastic.

 

All said above is correct. Older trucks had metal gears. Ours are plastic (nylon blend) from Ford and I think aftermarket ones are plastic only. The rim size doesn't matter, it's the "rolling diameter" of the current tires that matter compared to original. In theory you were sold tires comparable to what you had before, so your speedo should be real close. Drive it and check if it is correct. Each tooth on the speedo driven gear is 3 to 4 MPH. More teeth slows the speedometer, less teeth speed it up. Ford used 16-21 tooth driven gears. As of 10/2018 when I retired as a Ford parts man, all were still sold by Ford. Something like $5.00 to $6.00 dollars each. But as I recall they were packaged in pairs. Your local Dealer may make you buy both. I wouldn't have, but I'm retired. 41 years was enough.

 

In my 69 I have the screw in type 9 speedo with the metal gear in my C6. I can't find a speedo gear for this thing and also I need like a 13 or 14 tooth gear. I found a company in Denver that makes a devise to correct any speedo inline of the cable. Screws into the trans/cable into the little box. Easy 2mins install. Hope this helps you guys.

https://speedometercablesusa.com/gear_box_adapters.html