1971 - 1974 Firebird Muncie Four Speed Transmission, M-21
Complete original GM Muncie M-21 4-Speed Transmission for your 71 - 74 Firebird or Trans Am. Professionally rebuilt and guaranteed for 1 year. If you want to race or speed shift a transmission at 6000 RPMs, DON'T BUY A Muncie. For Street Applications they are perfect. Features a 2.20 first gear and will have the side cover for your TCS switch.
*Please double check your clutch and pressure plate set to match below
71-74 M-21 ~ Input Shaft = 1 Grooves with Fine 26 Spline Count and 32 Spline Tail Shaft
Main Case = 3925661
***Note: This Transmission is shipped factory direct. Please allow 4-8 weeks for delivery. Shipping charges will apply for all in-store pickups and show deliveries.
PART NUMBER: TRA-613
- The Muncie M20 is basically a wide-ratio transmission and was intended for normal street driving use. The M20 units have a 2.52:1 first gear. The M20 is most compatible with GM 3 Series rear end differential gear ratios such as 3.08, 3.31, 3.55, 3.73, etc. They are for economy and street drivability and just cruising.
The Muncie M21 is a close-ratio unit, ideally designed to be matched with lower gear ratios such as 3.73, 4.11, or 4.56 GM 4 Series rear end differential gears. The M21 units have a 2.20:1 first gear. A close-ratio gearbox keeps shift points closer together, which keeps rpms up. The M22 has higher-nickel-content straight-cut gears. It uses much the same gear ratios as the close-ratio M-21, but can take more abuse. An M22 retains less heat due to its straight-cut gears and the lack of thrust that helical-cut gears create. An M-22 holds up really well, the downside is it tends to make noise. It will rattle at low rpms and whine at high rpms.
The Muncie M22 is also a close-ratio unit, ideally designed to be matched with lower gear ratios such as 3.73, 4.11, or 4.56 GM 4 Series rear end differential gears. The M22 units have a 2.20:1 first gear. The M22 is the one and only "Rock Crusher". Some people think all Muncie four-speeds are Rock Crushers, but they're not.
*PLEASE NOTE ~ THIS TRANSMISSION IS SHIPPED DRY. ALWAYS USE REGULAR 80 / 90 GEAR OIL SIMILAR TO OUR DRIVEN PART # 04530.
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