What color are my teeth? Speedo gear.
 

I need to purchase the correct speedo gear for my 1970 T/A with an M-20, 3;55 rear gears and 25.5 inch tall tires (15" rally 2s). Looking at George Pearsons Speedo gear chart I need either: Blue with 20 teeth "WB code, or Green with 22 teeth "WL" code. I do not know what the "WB" or "WL" codes refer to. Anyone here know what speedo gear I need for an accurate speedometer reading? Thanks.

You’d also need to know the number of teeth on your drive gear (on the output shaft inside the tail). You should be able to remove the driven gear housing and will be able to see what color it is but I’ve seen a few variations as in, the same number of teeth being two different colors. You could raise the rear axle and spin the tires to turn the output shaft and count the number of teeth.

Lastly, this kit come with several driven gears you could easily swap out till you get one that works for you.

https://www.ebay.com/itm/13265705988...mis&media=COPY

I believe there are 8 teeth on the drive gear. Dave

I believe you’d need a 22 tooth driven gear then. You can find online calculators to help you if you search for speedometer gear calculator.

WB is the wide ratio. WL is the close ratio. There should be a metal tag (with PN and pick code) on the transmission side cover bolt denoting such. Also stenciled on the transmission.

/\ HFR nailed it;
I have rarely seen the stencil, but if the tag is missing, the Muncie code should be stamped.

According to the MPC I have here:
the WL w/3.55 gears (and F60/15 or F70/14* tires) used a green 22 tooth gear (#3860345)
the WB w/3.55 gears (and F70/14* tires) used a natural 19 tooth gear (#3860342) with an adapter
the WB w/3.55 gears (and F60/15 or E78/14** tires) used a blue 20 tooth gear (#3987920) with an adapter

* = Formula availability only
** = base or Esprit only

Green gear with 22 teeth it is then! Thanks again everyone I really appreciate your help. Dave

Green Teeth, there was a 1973 Charlie Daniels song, Uneasy Rider that had a character named "Ole Green Teeth". He might also had 22 teeth, they never reveal that in the song.....;)

After reading the thread i just had to go to You Tube and play it once, funny song, I haven't heard for many years.

:focus:

From the factory speedometers tended to read high by up to 5 mph at 60. This was allowed. Reading too low was NOT allowed. Accuracy from 0-35 was not good.
Also Bias ply tires sit a little taller than their radial counterparts.
Only Police cars had certified speedometers at this time, and not many dealers certified them, and GM didn't till much later.
So... don't expect exact speed to show..