I've recently changed out the 3rd member from a 3.54 to a 2.50, my speedometer is way off. I was talking to a speedometer place and they recommened that I change my drive gear out from a 7 tooth to a 9 tooth. They said it would be very close to being accurate. I have not had any luck finding a 9 tooth gear. The teeth need to be angleing toward the left if you're holding the keyway (slotted little ball hole) toward your left hand or your right hand. Any help with this part (and part number) would be greatly appreciated, otherwise this will cost a small fortune (almost $300.00) to get what I need from the speedometer specialist. Thanks for all your help. Kevin Felix

 

Not sure friend try Partsvoice.com, hey I'm interested in that 3.54 rig I'm in S.C. gayle.sutton@am.jll.com thanks

 

Do you mean the drive gear or the driven gear?
The drive gear is cut into the output shaft. Not easily changed, have to disassemble the transmission.
The driven gear is on the end of the speedometer cable, and is very easy to change.
What size is your driven gear?
And, what transmission do you have?

 

My transmission is a NP-435 (standard 4 speed) the original drive gear is yellow and is a 7 tooth plastic gear. The driven gear (pencil gear) is a green 17 tooth gear. I need a 9 tooth drive gear that the gears run off right to left regardless of how you hold the gear with the key hole (ball) faceing your left hand or your right hand. Do not know if they were or are made. The speedometer specialist said this would be the simplest and least expensive thing to do and it would be pretty close to being accurate. Please help thanks Kevin Felix

 

No such thing as a 9 tooth DRIVE gear for your application, 6, 7 or 8 tooth only. I couldn't find any DRIVE gears for anything w/9 teeth in the 1964/72 truck catalog.

You may be able to get a 9 tooth DRIVE gear from a speedo shop or autoparts store, but make sure the inside/outside diameter is the same and the teeth run the correct way.

Some run: //// some run: \\\\

Ford has used the same nylon DRIVEN gears since 1960. 16 thru 21 teeth are available. The prices range from $2.02 to $4.50 each.

 

Thanks Bill for that info. What do you think about a 8 tooth drive gear and a 16 tooth driven. I do not know how to figure the gear ratio. My tire size is 235 75R/15 , rear gears 2.50, transmission NP-435. If this info will help anyone out there it is appreciated. The original was NP-435, 7 tooth drive, 17 tooth driven gear, tires do not know (when I purchased had 235 75R/ 15) but I'll leave the tires as is. If anyone can do the math on this problem please help. Kevin Felix

 

Bill (NB) or anyone else can you tell me where I can purchase a 16 tooth driven (pencil) gear and a 8 tooth drive gear it would be of great help. Thanks again for with all your help, wisdom and knowledge. Kevin Felix

 

This should help. Plugging in the tire diameter which i believe is approximately 28 inches in your case, i come up with an 8 tooth drive gear and a 14 tooth driven gear. Since you can only get a 16 tooth driven gear, it will still be off slightly but should be a lot better than it is now.

Speedometer Calibration Program - Method 1

 

CODZ-17271-A .. 16T Nylon Speedometer Driven Gear / Available from Ford.

MSRP: $4.34 // FTE sponsor PARTSGUYED.COM price: $3.12.
----------------------------------------------------------
There are myriad different 8T drive gears. I need to know the I.D. & O.D. of the 7T gear you have now to find an 8T that will be compatible.

 

I belive we have solved the problem with some help from others. I went to partsvoice .com and 2 people (autodealers) referred me to blumenthal transmission in OKC,OK. Just happened to get ahold of a gentlemen by the name of Roger ( he's referred to as the man who knows NP-435). He did a little looking while I was talking with him and came up with a blue 9 tooth drive gear that will work on my setup without any modifications. It should be at my place tomorrow and I'll report back if it works or not. Thanks Kevin Felix

 

I'm familiar with Blumenthal as they have Timken rear axle parts that are the same for 1940/50's 'big' Ford & Studebaker trucks.

 

1rst time to visit with blumenthal hopefully they are as good as they came recommened. I'm excited to be able to drive my old truck, A/C in, most the body work done and painted (2 tone), and hoping for a accurate to close speedometer. Its almost ready to take off. I do not know how to post pictures of the old truck or I would be willing to try, how about some help in this area. Thanks for your help in advance Kevin Felix .

 

Quote:
Originally Posted by 76f350spercamprspeal

Welcome to FTE, Best Damn Forum EVER!
------------------------
Here's How to Post Pictures:
1. Login to FTE.
2.Click User CP (In the Top Left Hand Corner)
3.(On the Left, There will be a list, The 5th Option Down, will say "Pictures & Albums) Click That.
4.Then, Click Add Album, Enter a title, and description, if ya want to.
5. Click Upload Pictures, Then click Browse, Locate the Files of your truck. (You can add 3 files at a time)
5. Click Upload.
6. Add a description to the individual pictures, then click save.
7. Add more files if ya want.
8. Click The Picture you want to post, it will give you two codes at the bottom, Right Click The Second one (It say's BB Code, Then Say's [IMG]http:blahblahblah...[/IMG])
Then, Once that is highlighted, Right Click, Then Copy, Then Paste it into your post.
You can add up to 30 Images in one FTE Post.
If, Ya need any help, Don't hesitate to ask.

 

Well I belive it worked ( will see in a couple of months), my speedometer , according to my GPS, is off 2 mph at 68mph. When traveling 68 according to my speedometer, my GPS reads 70 mph. Then at 28 mph to 29 mph my my GPS reads 30. So if the blue 9 tooth rear drive gear holds up, meaning that the gear does not strip out, then it worked for me. Thanks for all your knowledge and willingness to help. Kevin Felix

 

Artic y block or anyone else, I was able to get a pic of my truck in my album (do not know exactly how) but, do not know how to get it to a new thread. I'd like to do this so I could share with all you folks. Please help with your knowledge and kindness, its much appreciated. Your friend Kevin Felix