New transmission speedo gear for your classic. Correct red color and 21 tooth design. Exact fit for all automatic powerglide , turbo 350 and saginaw or muncie manual transmissions. Will not work for automatic turbo 400 transmissions. Factory match for 3.31 rear axle ratio with stockish size tires. You may have to do some trial and error. See gear selection chart in the installation and info tips on the home page. Replaces original GM part number 3987921 perfectly.
Installation Tips :
To check your Drive Gear designation/size to determine if you have a 1.84 or a 1.76 gear, from outside looking through the hole/opening, use a cardboard gage and measure the width. The 1.84 is 0.610" wide and the 1.76 is 0.531" wide and both have a 8 tooth count.