Muncie was a popular transmission manufacturer back in the day. They produced both the M20 and M21 transmissions. However, many people are unsure of the difference between these two transmissions. The main difference is that the Muncie M21 has a higher gear ratio than the Muncie M20. The Muncie M21 also has a stronger construction and can handle more power than the Muncie M20.
In this blog post, I will explain everything you need to know about the Muncie M20 and M21 transmissions! So, without further ado, let’s jump right in!
Comparison Table Between Muncie M20 and M21
| Muncie M20 | Muncie M21 | |
| 1st gear ratio | 2.52:1 | 2.20:1 |
| 2nd gear ratio | 1.88:1 | 1.64:1 |
| 3rd gear ratio | 1.48:1 | 1.28:1 |
| 4th gear ratio | 1.00:1 | 1.00:1 |
| Reverse gear ratio | 2.59:1 | 2.27:1 |
| Input shaft spline count | 26 | 27 |
| Output shaft spline count | 32 | 32 |
| Oil capacity | 1.9 pints | 1.9 pints |
Detailed Comparison of Muncie M20 & M21
When choosing the right gearbox for your car, you might wonder what the differences are between the Muncie M20 and M21 gearboxes.
While both options are great choices, there are some key differences that you should be aware of before making your final decision.
1. Input shafts
The M20 and M21 both have 26-spline input shafts. However, the M21 has a higher torque capacity due to a stronger input shaft. The M21 will also have a different gear ratio than the M20, typically a higher numerically-higher gear ratio. This results in slightly better fuel economy and slightly lower engine speeds at highway speeds.
So, while there are some differences between the M20 and M21 in their input shafts, they are not major differences. Both transmissions will provide good performance and reliability. Also, you can reach out more about the motor engine and its other accessories on Motopickers.
2. Output shafts and Gears
There is a difference between Muncie M20 and M21 output shafts and gears. The M21 has a higher gear ratio than the M20, which means that the M21 will have a higher top speed. The M21 also has a stronger gear set, handling more power and abuse than the M20.
When you are looking for a Muncie transmission that can handle more power and abuse, then the M21 is the better choice. However, if you are looking for a Muncie transmission with a higher top speed, then the M20 is the better choice.
3. Gear Ratios
Muncie M21- The Muncie M21 is a close-ratio transmission with a gear set having a 3.36:1 ratio first gear and 0.68:1 ratio fourth gear suitable for high-performance cars.
Muncie M20- The Muncie M20 is a wide-ratio transmission with a gear set having a 2.52:1 ratio first gear and 1.91:1 ratio fourth gear suitable for street cars. M20 transmissions were also used in some muscle cars and other vehicles.
Their gear ratios are major differences between the Muncie M21 and the Muncie M20. Also, the Muncie M21 has a close-ratio transmission with a gear set that has a 3.36:1 ratio first gear and 0.68:1 ratio fourth gear.
The Muncie M20 has a wide-ratio transmission with a gear set with a 2.52:1 ratio first gear and 1.91:1 ratio fourth gear.
4. Clutch discs and pressure plates
Clutch discs are an often misunderstood but integral part of a Muncie M20 or M21 transmission. Clutch discs transmit torque from the engine to the transmission while allowing for smooth engagement and disengagement of the clutch. It also helps to cushion the engine and transmission from shock loads.
Two clutch discs are used in Muncie M20 and M21 transmissions:
- Clutch disc with spring damper
- Clutch disc with diaphragm damper.
Clutch discs with spring dampers are the original type of clutch disc used in Muncie M20 and M21 transmissions. These clutch discs have a series of springs that act as a cushion between the engine and transmission.
5. Weight
The Muncie M20 and M21 transmissions are four-speed units designed for use in General Motors vehicles. Though they share many similarities, there are a few key differences between them. One of the most notable is their weight.
The M20 transmission weighs approximately 140 pounds dry, while the M21 transmission weighs approximately 155 pounds dry. This difference in weight is because the M21 has a stronger gear set than the M20.
This stronger gear set gives the M21 transmission greater durability and longevity, making it the preferred choice for high-performance applications.
6. Cost
The M21 transmission is more expensive than the M20. The M21 is a close-ratio transmission, while the M20 is a wide ratio transmission. The M21 is also made of stronger materials to handle more power. The M21 is better for a performance car, while the M20 is better for a street car.
Muncie M20 VS. M21 Transmission: Which is Better?
There is no easy answer when deciding whether a Muncie M20 or M21 transmission is better in terms of overall performance. Both transmissions have unique strengths and weaknesses that must be considered when deciding.
Ultimately, the best decision will come down to personal preference and the type of performance most important to the individual.
Some people may prefer the Muncie M20 because it offers a higher top speed. The M21 is geared more towards acceleration, so it may not be the ideal choice for someone who values top speed above all else.
Others may find the M21 the better option because it offers better fuel economy. The M20 is geared more towards performance, so it may not be as fuel efficient as the M21.
How much HP can a Muncie M20 handle?
The Muncie M20 is a very strong and durable transmission that can handle a lot of HP. It is often used in high-performance applications that can handle more than 700 HP. It is also a popular choice for off-road applications, whose strength and durability are greatly appreciated.
How do you tell a Muncie M20 from M22?
You must look at the gear ratios to tell a Muncie M20 from an M22. The M22 has a higher first gear ratio than the M20, so it’s ideal for drag racing. The M20 is better suited for street driving because it has a lower first gear ratio and thus provides better acceleration.
Another way to tell them apart is by looking at the input shaft. The M22 has a 26-spline input shaft, while the M20 has a 10-spline input shaft.
Finally, the M22 is usually painted red, while the M20 is usually painted blue.
What is The Difference Between A Muncie M20, M21, And M22?
There are three types of Muncie transmissions, the M20, M21, and M22.
About Them!
- The M20 is the basic model of the Muncie four-speed transmission. It was designed for light-duty use with engines that produce up to 260 ft. lbs. of torque.
- The M21 was designed for heavier duty use with engines that produce up to 300 ft. lbs. of torque.
- The M22 was designed for even heavier duty use with engines that produce up to 600 ft. lbs. of torque.
Main Difference
The main difference between the M20 and M21 is the gear ratios. The M21 has a closer ratio than the M20, which makes it better suited for high-performance applications. The M22 has an even closer ratio than the M21 and is ideal for drag racing or other high-performance uses.
In Terms of Input Shaft,
The M20 and M21 use a 26-spline input shaft, while the M22 uses a 32-spline input shaft. The larger spline count on the M22 makes it stronger than the M20 and M21 and less likely to strip the gears under high stress.
Oil Pump
The M22 also has a higher capacity oil pump than the M20 and M21. The higher capacity pump is necessary to lubricate the larger gears in the transmission properly.
The Muncie transmissions are not interchangeable. The M20 and M21 will bolt up to any GM engine, but the M22 will only bolt up to engines with a bell housing designed for an M22 transmission.
Close Ratios
The Muncie transmissions are highly sought after by performance enthusiasts. The close ratios of the M21 and M22 make them ideal for high-performance applications, and the strength of the M22 makes it a good choice for drag racing or other extreme uses.
How Much Gear Oil Does A Muncie 4 Speed Take?
The Muncie 4 speed was introduced in 1963 and used until 1974. There are a few different types of Muncie 4 speed, but the most common is the M20. The M20 has a 1-1/8″ input shaft and a 26-spline output shaft.
The Muncie 4-speed takes approximately 3 or 1.42 liters of gear oil. This includes the oil that is in the torque converter. Using the correct type of gear oil is important, as using the wrong type can cause damage to the transmission. The most common type of gear oil to use in a Muncie 4 speed is 80W-90.
How can you adjust a 4-speed transmission?
There are a few ways to adjust a 4-speed transmission, depending on what needs to be adjusted.
- First, check the fluid level and condition.
- If it is low or dirty, flush and refill with fresh transmission fluid.
- Then, check the clutch pedal free play.
- When the pedal has too much free play, adjust it according to the manufacturer’s specifications.
- If the pedal has too little Freeplay, bleed the clutch system according to the manufacturer’s specifications.
- Finally, adjust the shift cable according to the manufacturer’s specifications.
Final Words
If you have a Muncie M20 transmission, take care of it and keep it well-maintained. Finding parts for this transmission may be difficult, so be prepared to do some digging if something goes wrong.
The Muncie M21 is a better option if you want an upgraded transmission; it has an overdrive and will last longer than the M20.
