So I've done some research. Here is a formula to figure out what speedo gear you need.

(correct speed/indicated speed)current speedo teeth = needed speedo teeth.

I used this calculator to determine indicatied speed and actual speed. I basically did a before and after one on each side of the sheet.

Gear Ratio Calculator

Using 2500 rpms as a baseline I figured out indicated speed and actual. I also removed and counted the teeth on my speedo gear. (20T)

(65mph/55mph) x 20 = 23.6

So I'll round up to 24 as I will only go bigger on tire size not smaller.

Anybody know where I can get the gear?

 

There isn't a 24 tooth gear available, 23 is the biggest. And the 23 has a reputation of not lasting very long. What you'll have to do is replace the drive gear or use a ratio correcter.

 

The drive gear on the transmission shaft? With what? How do I determine which of those?

The current one is yellow.

 

E1TZ-17285-A .. Yellow DRIVE gear / 8 teeth, run this-away ////

Nylon DRIVEN gears: 16 thru 21 teeth available. Same gears have been used since 1960, all available from Ford.


LeBaron: No, not yet.

 

So then what do I need to do if i want to get my speedo accurate?

 

You need to swap in a 9 tooth if your speedo is slower than your going. Mine had a 9 tooth and was reading to fast so had to order an 8 tooth. If you read post #13, I think that's the one, NumbersDummy gave me a few places that carry the gears. And I think he just posted that Ford still carried them also. Just make sure you get the one like you have. Some go //// and some \\\ and ND said yours is this way ///.

 

Awesome thanks for the help guys. 9 tooth. Then what driven gear?

 

Well I ended up getting this link from another board. These guys were really helpful and knew exactly what I needed. Quick phone call took care of it.

Speedometer Gear, Speedometer Gears, Ford, GM, Dodge 700R4

 

So, pray tell, what did you order?

 

Well I did my calculation backwards. Also my drive gear is in fact 7 teeth.

So all I needed was a 17t driven not a 23t like I thought. Glad I called those guys. When we get the tranny back together I'll report back for closure.

 

Hello Gary, I know this is an older post but I was searching on how to adjust the speedometer reading. Right now I know that when the Speedo says I am going 55 mph I am actually going 43 mph. The trans is a NP435, 31" tires. I'm not sure on the rear end. I've seen the calculators and know that part, my question is how and where is the gear that I have to replace? I've followed the speedo cable to the trans but didn't see where or how the gear comes out. Thanks in advance for helping a newbie out!

 

This is an easy one. There is a small bolt holding a piece of metal with a semi-circular cutout on the end of it. That cutout is over the end of the cable holding it in the tranny. Pull the bolt and the holder, and then pull gently on the cable. You might have to wiggle it a bit to get it to come, but it will slide right out. The gear is held on the end of the cable with a clip. Be sure and lube the o-ring when you put it together.

 

[QUOTE=Gary Lewis;13374859]This is an easy one. There is a small bolt holding a piece of metal with a semi-circular cutout on the end of it. That cutout is over the end of the cable holding it in the tranny. Pull the bolt and the holder, and then pull gently on the cable. You might have to wiggle it a bit to get it to come, but it will slide right out. The gear is held on the end of the cable with a clip. Be sure and lube the o-ring when you put it together.[/QUOTE

Thanks, for the quick answer, i've been pretty busy with the family and I probably won't get to it till next week, but I will keep you posted and probably ask more questions.