speedometer gear ???

[Norris W.]

First of all, I must not know how to use the search function, but tried several years, plus date ranges for key words speedometer gear and the board does nothing except I get a "done" at the bottom.

Anyway, how do I know what gear to use in a '63 T10 with 3.36 gear? The vendor I usually use has the same gears listed in several different colors and the phone person doesn't know either.

[Joe L.]

Re: speedometer gear ???

Norris------

I'm away from home right now and can't check my references. However, I'm pretty sure you need a 20 tooth BLUE driven gear. However, keep in mind that this gear will only mesh with a certain DRIVE gear. If the transmission has always been installed in front of a 3.36:1 rear gear ratio, all is well. If, however, the transmission has previously served with a 3.70 or numerically higher ratio, the internal DRIVE gear may not be correct for the 20 tooth DRIVEN gear.

[Terry D.]

Re: speedometer gear ???

Norris

Joe is correct, as usual, it is a 20 tooth dark blue gear.
Terry

[Norris W.]

Re: speedometer gear ???

Thanks for the reply. That brings up a question from another one of my projects then. How many different drive gears are there. I see one listed for 3.08 through 3.55, but no listings above. I've probably got some laying around that came from 3.70 cars, but will need one for 4.56. How far does the 3.70 & up gear reach as far as ratio?

[Joe L.]

Re: speedometer gear ???

Norris------

For T-10 applications, there are at least 2 and, possibly, 3 or more DRIVE gears. The common ones are the '44' and '45' gears (representing the last 2 digits of the GM part number). Both of these gears have 8 teeth. However, one is slightly smaller in OD than the other. The smaller gear meshes with the larger DRIVEN gears which are the larger tooth count gears from 22 (green) to 25 teeth. These generally are used with 3.70 and 4.11 rear ratios.

The larger DRIVE gear meshes with the smaller diameter DRIVEN gears and of 18 to 22 (silver) tooth count. These are generally used with rear ratios of 3.08 to 3.55.

My vague recollection is that 4.56:1 rear ratios require a special DRIVE gear and special DRIVEN gear. This DRIVE gear is of different tooth count than 8 (might be 6 or 7) and the DRIVEN gear might be steel instead of nylon like most of the gears.

All original T-10 and 63-67 Muncie DRIVE gears are steel. Both T-10 and 63-67 Muncie use the same DRIVE gears.

[Michael B.]

Re: speedometer gear ???

You can do a search for GM Speedometer Gears for part numbers and color references.

This Chevelle site shows the drive gear diameters and what driven gears matches the drive gears.

http://chevelleengineer.home.comcast.net/speedo.htm

[Wayne M.]

4.56 drive / driven set

You don't mention if your "other" project is a Muncie or T-10, but I believe this set will fit both tranny manufacturers, per GM catalogs.

The drive is 3845079 (6 teeth) The driven is 3860329 (20 teeth).