I have a real conundrum here! The Driven gear on my speedometer sheared and I attempted to replace it with another gear only to find there are a huge number of different colors and sizes. The dealership will not identify the exact one for my car. What I was able to recover was a black driven gear shaft, but there are several gears from 42t, 23 teeth 22 teeth 20 teeth Etc that are all black in color! I am told that the only way to match it is to determine which type of transmission is in my car, but unfortunately there's no way to tell unless I remove the transmission. Can anybody give me an idea as to: A) which transmission is in my car? (it is a hydramatic with overdrive) And B) which of the several black driven gears would be the one for that transmission? The shop already had a 40 tooth gear which was way too large, so we're looking at probably 23, 22, 20 or 19. Any help would be very much appreciated!

 

The speedo driven gear varies depending on the rear axle ratio and the tire diameter (in addition to which transmission you have). You need to know this information to figure out which gear you need.

 

Joe, you are amazing! From the very first chart that you presented I was able to find the proper gear! According to that list there are only two black gears listed, one is a 27 tooth and the other is a 40 tooth. Since the latter one did not fit because it was too large to even go through the gear housing hole, by simple deduction the other gear is the proper one! I'm lucky that the gear shaft was still available from the original, or else I wouldn't have even been able to figure out what color I needed. Thanks again sir, you are always a wealth of information.

 

It will be the 27 tooth Black gear. Use this calculator for the 2004R transmission. https://www.google.com/url?sa=t&sour...7EpTdk2RWKk13V
You just need to find out your tire size and rear gear ratio