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| − | == GENERAL MOTORS TRANSMISSIONS ==
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| − | == Preamble == | + | ==Preamble== |
| − | The History of the Hydramatic transmission began back in 1932 where it was introduced by Cadillac as the “shiftless transmission”. Anyone want to read about its history should go to this link, http://en.wikipedia.org/wiki/Hydramatic . The scope of this article is mainly centered around the transmissions of the 60’s to present date, however, if there is interest in prior years it can certainly be included. | + | The history of the Hydramatic transmission began back in 1932, when it was introduced by Cadillac as the "shiftless transmission". For more historical information, see [http://en.wikipedia.org/wiki/Hydramatic Hydramatic transmission at Wikipedia]. The scope of this article is mainly centered around the transmissions of the 60's to present date. However, if there is interest in prior years it can certainly be included. |
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| | This article will concern itself with the different types of transmissions used by General Motors, and their physical and mechanical properties. | | This article will concern itself with the different types of transmissions used by General Motors, and their physical and mechanical properties. |
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| | First, a transmission is a way of applying torque from an engine through a differential to a wheel, causing forward (or reverse) motion of a standing body. | | First, a transmission is a way of applying torque from an engine through a differential to a wheel, causing forward (or reverse) motion of a standing body. |
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| − | == 1. Types of Transmissions == | + | ==Types of transmissions== |
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| − | ==1-A. Standard == | + | ==Standard == |
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| − | == Three Speed == | + | ==Three speed== |
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| − | [[Image:64_Nova_3_sp.jpg]] [[Image:64_Nova_3_sp_number.jpg]] [[Image:64_Nova_3_sp._shift_levers.jpg ]] | + | [[Image:64_Nova_3_sp.jpg]] |
| | + | [[Image:64_Nova_3_sp_number.jpg]] |
| | + | [[Image:64_Nova_3_sp._shift_levers.jpg]] |
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| | From a 1964 Nova 342 Saginaw. | | From a 1964 Nova 342 Saginaw. |
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| − | == Four Speed == | + | ==Four speed== |
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| | Manual Transmission Identification & Description | | Manual Transmission Identification & Description |
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| − | [[Image:Muncie_M20_4_speed.jpg]] [[Image:Saginaw2.jpg]] [[Image:Borgwarner.jpg ]] | + | [[Image:Muncie_M20_4_speed.jpg|Muncie]] |
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| + | [[Image:Saginaw2.jpg|Saginaw]] |
| − | Muncie (left) Saginaw (center) Borg Warner (right)
| + | [[Image:Borgwarner.jpg|Borg Warner]] |
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| | The Muncie reverse lever is in the extension housing, and the cover has 7 bolts. While looking at the cover, 3rd/4th gear lever is on the left. 1st/2nd gear lever is on the right. | | The Muncie reverse lever is in the extension housing, and the cover has 7 bolts. While looking at the cover, 3rd/4th gear lever is on the left. 1st/2nd gear lever is on the right. |
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| | The Borg Warner has a 9 bolt cover. | | The Borg Warner has a 9 bolt cover. |
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| − | == Borg-Warner == | + | ==Borg-Warner== |
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| − | ==Muncie ==
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| − | The Muncie 4-speed transmission was used with many different GM models and engine combinations from 1963 through 1974. The basic design and operation theory of the gearbox changed little during this period, however several design upgrades and modifications were made during the total production run. The Muncie was used with most performance engines, and is not to be confused with the Saginaw or Borg Warner 4-speeds.
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| − | The Muncie is distinguished from the Saginaw in that the reverse lever on the Muncie is mounted in the extension housing, where the Saginaw reverse lever is mounted in the side cover. The main difference between the Muncie and the Borg-Warner is that the Muncie has a 7-bolt side cover and the Borg Warner has a 9-bolt side cover.
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| − | 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. Axle ratios of 3.73 and lower (numerically higher) came with close-ratio transmissions, while axle ratios of 3.55 and higher (numerically lower) used wide-ratio transmissions. In addition, many GM high-performance engines came with M-22 “Rock-Crusher” in the 1970-73 years, however an early version of the M-22 was available as early as 1965 in Corvettes.
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| − | Proper identification of the transmission type is absolutely necessary, but sometimes difficult due to several factors. First, GM used several different methods to label and identify transmissions from year to year and model to model. Unfortunately the identification systems seem to have many exceptions, rendering them virtually useless to the restorer. In addition, due to engine and transmission swaps, and modifications that occur over the years many cars do not carry the original drive train that they were produced with.
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| − | For example, due to interchangeability, a 1969 Pontiac could have a trans case and gears from a Buick and a rear housing (extension) from an Oldsmobile. Several production changes through the years that effect the external appearance may also cause additional confusion when identifying a particular transmission:
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| − | 1. Both single and dual drain plugs were used.
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| − | 2. Speedometer adapters were used on either sides of the rear section (extension).
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| − | 3. Side covers were sometimes secured with studs and nuts, other times with bolts.
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| − | 4. Input shafts may be fine or coarse spline. Output shafts may be large or small. Combinations of these vary.
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| − | 5. External shift levers are secured with studs and nuts, others with bolts. Some levers are long and some short.
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| − | 6. Input shafts may have 1 ring, 2 rings, or no rings at all.
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| − | Muncie identification (Three 4 speeds were offered.)
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| − | The M-20 wide ratio, the M-21 close ratio, and the "Extra heavy duty close ratio" M-22, also known as the "Rock Crusher". The M-22 was generally installed behind severely powerful (high torque) big-block 396 and 454 engines. The M-22 is distinguished from an M-21 by the angle of the gear teeth. The M-22 has "straight cut" gears and tends to be noisier.. The M-21 has a higher pitch angle on its gear teeth. The close ratio M-21’s generally came with 3.73 ratio & up cars. While, 3.55 geared & under (numerically lower) cars used the wide ratio gearbox.
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| − | Due to the wide combination of id's, stampings, numbers, varied and even GM couldn't keep track, it's best to ID your gearbox visually. The best way to ID the transmission is to, count teeth.
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| − | Muncie 4 speed spline, groove and tooth count characteristics.
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| − | Type/Year Input Spline Input Groove Input Gear
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| − | Tooth Count Cluster Gear
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| − | Tooth Count Output Spline Gear Ratio
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| − | M20: 1963 - 65 10 none 24 29-22-19-17 27 Note 1
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| − | M20: 1966 - 70 10 2 21 25-22-19-17 27 Note 2
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| − | M20: 1971 - 74 26 2 21 25-22-19-17 32 Note 2
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| − | M21: 1963 - 70 10 1 26 27-22-19-17 27 Note 3
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| − | M21: 1971 - 74 26 1 26 27-22-19-17 32 Note 3
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| − | M22: 1965 - 70 10 none 26 27-22-19-17 27 Note 3
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| − | M22: 1971 - 72 26 none 26 27-22-19-17 32 Note 3
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| − | Note 1: M-20 gear ratio: 1st 2.56:1, 2nd 1.91:1, 3rd 1.48:1, 4th direct
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| − | Note 2: M-20 gear ratio: 1st 2.52:1, 2nd 1.88:1, 3rd 1.46:1, 4th direct, Rev 2.59:1.
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| − | Note 3: M-21/22 gear ratio: 1st 2.20:1, 2nd 1.64:1, 3rd 1.28:1, 4th direct, Rev 2.27:1
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| − | Effective October 21, 1968, an additional letter was added to the plant prefix number to help identify the gear ratios in Muncie transmissions. The additional letter codes as follows:
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| − | Muncie 3 speed Manual Muncie 4 speed manual transmissions
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| − | Suffix 1st gear ratio Suffix 1st gear ratio
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| − | A 3.03:1 A 2.52:1 wide range
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| − | B 2.42:1 B 2.20:1 close range
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| − | C 2.20:1 Rock Crusher
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| | + | ==Muncie== |
| | + | See: [http://www.yearone.com/updatedsinglepages/Id_info/muncie.asp Muncie 4-Speed Identification], [http://www.nastyz28.com/2gcog/trans.html Camaro Transmission Information and Restoration], and [http://www.yearone.com/yodnn/tech/VehicleInfoDecoding/GMMuncie4SpeedDecoding/tabid/349/Default.aspx GM Muncie 4-Speed Decoding]. |
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| − | '''Plant Codes and Prefixes:'''
| + | ===Plant Codes and Prefixes=== |
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| | Plant Type Prefix Plant Type Prefix | | Plant Type Prefix Plant Type Prefix |
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