1969 speedo drive gear for 3.73's

[Bryan302]

The P&A chart for speedometer drive gears for 3.73 with E70-15 tires is part#3924097 and driven gear is 3860346. 

The black 23 tooth driven gear 3860346 was relatively easy to get NOS.  My trouble is the drive gear.  My GM parts man tried to find the 8 tooth drive gear and came up with 3708145, which turned out to be the earlier steel gear without the spring clip.

Is the correct plastic drive gear for 3.73's part# 3924097, and is it Blue?  Is it 8 or 9 teeth?

If this 3924097 is correct, is there a replacement GM part number for the gear and clip?

I also found an 8 tooth drive gear, orange in color with a GM part#12338033.  I had no way to cross reference this part.

Please help!  Which is the correct mate to 3860346?  What color and number of teeth?

Thanks,
Bryan

[bcmiller]

I am not where I can look it up right now. I will respond this evening unless someone answers before that.

From memory, yes it is somewhat bluish.

Until then, read this.

http://www.cartechbooks.com/techtips/muncie-speedometer/

[L78 steve]

1.85” O.D. – GM #3924098 (later, #6261794); same “large” O.D.
          as #3708144, used the same range of 18-22-tooth “small”
                          DRIVEN gears, and was light green in color.

1.77” O.D. – GM #3924097 (later, #6261795); same “small” O.D.
          as #3708145, used the same range of 22-25-tooth “large”
          DRIVEN gears, and was medium blue in color.

Courtesy JohnZ

[Bryan302]

Bryon, that was a very useful article.  It cleared up compatibility issues with the two diameters.  Thanks!  Also, are most owners changing the plastic gear out with the earlier steel gear, as the article suggested?

Steve,  Thanks, that was exactly the information I needed.

Thanks,
Bryan

[bcmiller]

Bryon, that was a very useful article.  It cleared up compatibility issues with the two diameters.  Thanks!  Also, are most owners changing the plastic gear out with the earlier steel gear, as the article suggested?

Steve,  Thanks, that was exactly the information I needed.

Thanks,
Bryan

Not sure, but that plastic gear was a weak point. Makes sense to swap it out with a rebuild.