The Muncie SM420 is a heavy duty, four-speed manual transmission that was produced from 1947 to 1967 by General Motors for civilian use in a variety of pickup trucks, buses, dump trucks and heavy equipment. They were used in some military vehicles into the 1980s. It was replaced in civilian vehicles by the Muncie SM465 transmission in 1968.

The transmission has a 7.05:1 ratio first gear, which is one of the lowest "granny" gears ever produced in a production transmission. It weighs 135lb, which is 40 pounds less than the SM465 that replaced it. While the construction is dated by modern standards, these are sought after by off-road enthusiasts due to the ruggedness and gear ratios.^[1]

• 1st - 7.06:1
• 2nd - 3.58:1
• 3rd - 1.71:1
• 4th - 1.00:1

• Weight: 135 pounds
• Length: 10.4 inches
• Height: 17 inches
• Input shaft: 1 1/8 inch, 10-spline^[1]

• Muncie SM465 transmission
• New Venture Gear 4500 transmission
• List of GM transmissions

• The Novak Guide to the GM Muncie SM420

This truck-related article is a stub. You can help Wikipedia by expanding it.

• v
• t
• e