What are the gear ratios for a Muncie M21 transmission?

What are the gear ratios for a Muncie M21 transmission?

The 2.20:1 ratio first gear is usually referred to as the Muncie M21 transmission; based on GM’s production codes. The 2.56:1 ratio is referred to as the M20.

What is the difference between close-ratio and wide-ratio 4 speed transmission?

A: A wide-ratio transmission has a more drastic change in gear ratios between first and second, and third and fourth, with fourth gear being 1:1. A close gear ratio is more gradual, but again ending up at 1:1 in fourth gear. With a street-friendly gear like a 3.73:1 or lower, go with the close-ratio transmission.

How can you tell if you have a rock crusher M22?

Look for the “GM” sign imprinted on the transmission box to identify the manufacturer of the transmission. Check whether there are any rings around the shaft splines. An M-22 “Rock Crusher” has no rings, so if you see rings in your transmission, it means it is not an M-22 “Rock Crusher.”

What is a close ratio 4 speed?

The Muncie M21 and M22 Close ratio 4 Speed was the closest ratio 4 speed ever put into a production car. It’s ratios were 2:20 first, 1.64 second, 1.28 third, 1:00 fourth. If you plug those ratios into the formula in figure 1 you will end up with 25%, 22%, and 22%.

What gear ratio for Muncie?

In order for you to get a “close ratio” Muncie your car had to be equipped with at least a 3.70 rear end gear. You needed at least that low of a final drive to get your car moving. The “wide ratio” M20 had a 2.52 1st gear.

What kind of transmission does a Muncie 4-speed have?

Long boss bolt on type w/ Neutral Safety Switch. Muncie 4-speeds were produced in two different ratios wide-ratio (M-20) and close-ratio (M-21). An extra heavy duty close-ratio version (M-22) was also offered on many of the big-block high-performance models.The choice of transmission was dictated by the engine size and rear-axle ratio.

What is the effective first gear on a Muncie?

A wide ratio Muncie (2.52) with 3.42 rear would have an effective first gear of 8.6, the same rear with a close ratio Muncie first gear (2.20) would be 7.5. The higher effective first gear gives you better torque multiplication to get moving.

What’s wrong with the Muncie close ratio box?

The problem is that when the Muncie close ratio box was designed in the 1960’s we really didn’t worry much about gas mileage. In order for you to get a “close ratio” Muncie your car had to be equipped with at least a 3.70 rear end gear. You needed at least that low of a final drive to get your car moving. The “wide ratio” M20 had a 2.52 1st gear.