The SM465 is likely one of the most well known, most popular heavy duty 4 speed transmissions within the realm of the four wheel drive and off-road community. It was made from 1968 to 1991, with the 1968 to 1978 units considered early models and the 1979 - 1991 transmissions considered the late model do to minor changes. The early SM465 had a 10 spline output shaft for 4WD models and a 35 spline output for 2WD models, while the late model 4WD transmission used a 32 spline output shaft. In 1988, the cast iron top cover was replaced with a cast aluminum one, and it also was fitted with a different input shaft and bearing design. The "SM" in SM465 designates it as a GM synchro-mesh transmission. It is top loaded, extremely rugged, and has an impressive 6.55 : 1 "Granny" gear.
Muncie SM465 Transmission Ratios
1st |
2nd |
3rd |
4th |
R |
6.55 : 1 |
3.58 : 1 |
1.70 : 1 |
1.00 : 1 |
6.09 : 1 |
Muncie SM465 Transmission Specs
Transmission: |
Muncie SM465 |
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Type: |
4 speed manual transmission |
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Manufacturer: |
General Motors |
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Applications: |
1968 - 1991 Chevrolet/GMC pickups, Blazers, and Suburban, |
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Synchronized: |
Synchronized in all forward gears and reverse |
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Case Material: |
Cast iron case & top cover |
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Case Length: |
12.00" |
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Input Shaft: |
1 1/8" 10 spline input shaft, 6.5" stick-out |
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Max Input Torque: |
465 lb-ft |
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Output Shaft: |
• Early 4WD - 10 spline |
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Weight: |
~ 175 lbs |
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Fluid Type/Spec: |
50W or 80W-90 non-hypoid gear oil |
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Identification: |
Top loading transmission, early style had a cast iron top cover, while the later model had an aluminum top cover (both had a cast iron case). Standard H shift pattern with reverse toward the passenger and down. Trans has passenger and driver side PTO provisions. |
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