Is there a Chart to determine the correct Speedometer Pinion for a truck?

The truck in question is a 1974 W200 Power Wagon with 4.10 gears and 33" tires with a Manual transmission.

The chart in the tech archive only shows up to 30" tires.

the is a website----dodge jeep speedo---that lists virtually everything....

If the truck has the standard 3-position pinion adapter you need a 32 or 33 tooth pinion (actual math 32.57). I'd go with the 32.

Thanks savoy and John for the replies.

As best I recall, the speedometer pinion gear and cable housing are in / attached to the NP 205 Transfer case, but the truck is not nearby at the moment for me to verify.

I don't know if that makes a difference or not?

The truck has a NP 435 transmission and a NP 205 xfer case.

I have a personal copy of the 1974 Dodge Truck Factory Service Manual, and the Speedo chart indicates:

"Gear Teeth = 5" and "Pinion Teeth = 14" when used with 4.10 ring/pinion gears and 9.5" x 16.5" tire combination or,

"Gear Teeth = 5" and "Pinion Teeth = 15" when using either 8.00" x 16.5" or 8.75" x 16.5" tires and 4.10 differential.

And, of course, I have 33-inch tires, not 9.50 x 16.5's.

According to TireRack.com, 9.50" x 16.5" tires would be around 30 1/2" diameter.

I found a website for speedometer pinion gears, but not certain if this was THE one indicated in the reply post or not?

http://www.transmissioncenter.org/speedometer_gears_for_dodge_and_jeep.htm

In any event, appreciate the help.

speedo for 205 transfer case is a different animal---the info i gave you was for a automatic transmission....i have been needing to correct my 205 because of 3.08 gears...

Most 4 x 4 trucks used a gear box / speedometer adapter that would change the speed. There were like 3 or 4 different ratios. The truck book should show them.

The web site you listed shows the style pinion gear you will need. Then you will need a adapter box to tune it in. Here are the pinions you will use. I would find the smallest to spin the head the fastest. I would then run the cable direct and drive it with a GPS to see how far off you are. Then you can try a geared adapter or I believe there is a company that can custom build one for you.

You had the right web page you just need to go up.Here is what you need and you just need to figure the up or down percentage you need. You may be able to do that with the gear you have and the right percentage adapter.

#54RA2. If your truck tires have been switched to larger tires or you just need to speed up your speedometer this one will correct your problem. This part will speed up your speedometer reading. Use this one to convert MPH to Kilometers. Cost $88.00

Thank You. Really Appreciate your replies and thoughts and time spent on the subject.

I thoroughly looked over the website earlier in the day and saw the Adapters and gears.

Already thought about using my cell phone GPS speed application to roughly determine my GPS speed versus indicated speedometer speed.

Was hoping for a slightly more economical (than $88 plus tax and shipping) solution to the problem.

Around 15 years ago, I had a similar problem with my CJ5 and oversized tires. I took it to a Speedometer Shop where they added an Adapter, tested, calibrated and charged me around $140.

Figured I would try to determine how much I needed to slow down or speed up, and buy an adapter. Google Shopping showed an adapter for $62. Maybe I can find a cheaper one?

An alternative thought, was to consider that the existing Gear is 5-tooth, then figure out which Tooth Pinion gear that would work to produce the correct speed for 4.10 gears and 33 inch tires.

To further complicate the matter, I will likely be swapping to 35-inch tires at some point in the future. Would be great if I could update the adapter or gear for cheap or free when I do that change as well.

I may just try to get by using the Tachometer RPM to guess'timate speed until I buy 35 inch tires.

That's the problem. The 5 is fixed and there is only like 4 or 5 pinions available. You need an adapter geared for your tire size. So the gear alone wont do it.

Thanks again. Good to know. I may wind up buying the $88 adapter or a cheaper one if available.