Cangialosi explains there were two basic mainshafts produced for the M20, M21, and M22 transmissions (see Input Shaft Identification chart). The next set of numbers you will find helpful are on the flat part of the Distributor Deck. All rights reserved. 2.1Date codes 3GM transmissions, including Muncie M20, M21, M22 4Automatic transmissions 4.1AMC automatic transmissions, 1972-'06 4.2AMC automatic transmissions, 1955-'71 4.3Jeep automatic transmissions, 1971-back 4.4Transmission dimensions 4.4.1Ford 4.4.2MOPAR 4.5Ford automatic transmissions 4.5.13-speed identification 4.5.24-speed identification We are dedicated to giving you the technical support you need, when you need it! Please click Accept Cookies to continue to use the site. Typical Turbo 350 fluid pan. SECOND TRANSMISSION. The Turbo 350 quickly became known for its strength, versatility, and compactness. The SM465 is an outstanding, heavy-duty truck transmission designed and used in , 3/4 and 1+ ton trucks. Shown here is the M20 10-spline wide-ratio input shaft and counter gear. Once you identify the pan, count the number of pan bolts for confirmation. General Motors is an innovator in the automobile industry, and they were one of the early adopters of the automated transmission system. Muncie 4-speed or TH400 were the only transmission options available. It also uses the same vacuum modulator as the Turbo 350. $750.00 Automatic Transmissions Some transmissions may have a code stamped into their case or a tag riveted to them. According to Paul Cangialosi, Muncie transmission historian, technician, and author of Muncie 4-Speed Transmissions: How to rebuild and modify, the Muncie four-speed transmission has its roots back to 1935 and the U.S. patent number 3,088,336 along with an engineer named James W. Fodrea. However, there were several design upgrades and modifications made during the total production run. Glean the basics and use them in your research. 3.55 geared and higher (numerically lower) cars used the wide ratio gearbox. The main case will sport a seven-digit casting number (found above the US Patent No), which is not a GM part number. This one will have a CONveyor Number and beside that This version did not have a locking converter. Today that seems reasonable however $184.02 1965 dollars adjusted to 2015 dollars is a whopping $1,384.93. I definitely recommend a look at these transmissions, you've got to have a look. This includes but is not limited to Ford, Chevrolet, General Motors, Dodge, Mopar, or any other trademarked or copywritten content. The World's Best Chevrolet and GMC Club! case. According to Koval, the easiest way to identify an automatic transmission, though, is by transmission pan shape. Automatic transmission types are generally identified by their pan shape. The Muncie was originally a stronger alternative to the T-10 and Super T-10 because it could take the torque. Note the single groove, meaning an M21 close-ratio. Come join the discussion about restoration, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more! You don't have to search the classifieds or a junk pile to find a suitable bellhousing for your Muncie M20, M21, or M22. From left to right are the three basic Muncie input shaft/countershaft combinations. X3845157 GM. From 1971 through the end of production in 1974, the M20 got the 26-spline input shaft. From 1967 on, the ID number contained the transmission type or plant prefix, Date (coded below) and a shift code. (1: Chevrolet, 8: 1968, L: Van Nuys, CA, 165790: last 6 digits of VIN). If you do happen to stumble across Chevy four-speed at a swap meet, do you know what you are actually looking at? Casting Number Notes, 3831707 Early side cover; 1963 1965, 3884685 Early side cover; used with 3857584 tailshaft housing, 3950306 Late side cover no switches, 3952642 Late side cover with transmission controlled spark switch, 3952648 Late side cover with transmission controlled spark switch, 335308 Late side cover with neutral safety switch. They are notoriously very hard to read and often people make the mistake of thinking a '3' is an '8'. The 3L80HD would be the THM475 (heavy duty unit). Transmissions can be identified in the following manner: Casting numbers : Located on the case, extension housing and side cover (manual). On the right is the small input shaft bearing, which is 1963 only. Vehicles leaving the factory with an axle ratio of 3.55 and numerically lower gears, typically incorporated a wide-ratio transmission. Removal of the front bearing cover is where disassembly begins. General Motors has several transmissions, and they can be challenging to identify. On 72-77 vehicles, the switch is located over the accelerator pedal. +$20.00 shipping. Evolutionary designs came with unique pan shapes, which are clear indicators of which transmission you are dealing with. The optional 4-speed was a $184.02. THM350 - Medium duty 3 speed trans used from 1969 to 1989, Used in Buick, Olds, Pontiac and Chevrolet cars and Chevy & GMC light trucks until 1987. This is because the transmission lengths are the same and the positioning of the cross member can be easily modified, you only need to change the transmission mount, add transmission cooler lines, and update the shift indicator to a Turbo 350 pattern to complete the exchange. This is an M21 with 10-spline input shaft and cast-iron bearing retainer. The SM465 was made by General Motors from 1968 to 1991. In the early 90s, GM introduced its electronic Hydra-Matic transmission systems. fileslib. The materials used in case construction of a Muncie/Chevy four-speed mean that if you find one of these gear boxes in a shed or barn, the Muncie will probably be smooth and covered in grease and/or oil, while a Borg Warner or Saginaw transmission will usually be coated in a light layer of rust. They are found primarily in GM and Chevrolet trucks, Blazers, Suburbans and many other models falling under the 1/4-ton to 1-1/2-ton platforms. For 1971-'74, a larger diameter, 32-spline mainshaft was employed along with the corresponding yoke. Casting numbers on the case and extension housing. Looks to be from a 68/9 camaro. And keep in mind that not all will sport these grooves. Here's a typical Muncie gearset consisting of First, Second, and Third gear. Now, lets explore GM transmission identification, the different methods, and more. All transmissions with a 26-spline input shaft used a 32-spline output shaft, and all those with a 10-spline input shaft were paired with a 27-spline output shaft. When looking at a Saginaw transmission, the front input shaft will likely have oneor multiple grooves cut around its diameter. In fact, 1963 is a standalone year because changes in this box came almost immediately for 1964, beginning with the front bearing retainer, which was aluminum for 1963 and became cast-iron in 1964. All rights belong to the entity responsible for the trademark or copyright. Next, carefully raise the vehicle with a jack. Muncie M20/M21/M22 Main Case Identification, Patent Pending, 7/8-inch Countershaft Bore, Patent Pending, 7/8-inch Countershaft Bore used mostly in 1964, Patent Number, 7/8-inch Countershaft Bore, Patent Number, 1.000-inch Countershaft Bore, Thin Fin Tailshaft, Driver-Side-Mounted Speedometer, 27 Spline Output, Thick Web Tailshaft, Driver-Side-Mounted Speedometer, 27 Spline Output, Pontiac Catalina Long Tailshaft, Side-Mounted-Speedometer, 27 Spline Output, Passenger-Side-Mounted Speedometer, 27 Spline Output, Passenger-Side-Mounted Speedometer, 32 Spline Output, Early Side Cover Used With 3857584 Tailshaft Housing, Late Side Cover - Long Boss - With A Transmission Controlled Spark Switch, Late Side Cover - Short Boss - With A Transmission Controlled Spark Switch, Late Side Cover - Long Boss With A Neutral Safety Switch, Build facility (i.e., P = Muncie Transmission Plant), Month code it was assembled (i.e., 05 = May), Day code it was assembled (i.e., 25 = 25th Day), Month code it was assembled (i.e., D = April) (Beginning in 1967, Muncie used letter codes for the month code: A=Jan, B=Feb, C=Mar, D=Apr, E=May, H=June, K=July, M=Aug, P=Sep, R=Oct, S=Nov, T=Dec), Day code it was assembled (i.e., 12 = 12th Day), Month code it was assembled (i.e., M = August), Day code it was assembled (i.e., 03 = 3rd Day), Gear ratio set (i.e., A=M20) (This code was added to identify ratios. The vehicle identification number (VIN) is a unique identifier for each vehicle (VIN). Main cases manufactured prior to May 7, 1963, will say Patent Pending. The 26-spline input shaft yields greater torque capacity via the number of teeth and greater surface area. If you are not sure how to distinguish between an M20, M21, or M22 Muncie, knowing what to look for can be tricky. On the right is the M22 countershaft with 27-teeth. Report an Issue | The Muncie was used in all high performance applications until the Borg-Warner Second Design Super T-10 began replacing it in 1974. Generally used in straight and V6 and small block engines. When you purchase through links on our site, we may earn an affiliate commission, which supports our community. Engine Casting Numbers Explained 1954-1962 Chevrolet, Serial Number/Engine Type/Series Designation, On the flat part of the Distributor Deck you will find a stamped Serial Number. While the big-block vs. small-block variable is one that has two groups of passionatefollowers, the other reflects the way in which the driver selects transmission gears. 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The M-22 has "straight cut" gears. This is a large reason why some guys will not rely on transmission identification by the input shaft grooves. Muncie transmissions from 1971-'74 have the larger 32-spline output shaft. 60 is the strength rating (less than the 4L80). As a manufacturer, GM also applied numerous transmission systems in their older models. That being said, there was a second, close-ratio version (M22) that was developed to survive duty behind engines with a higher torque output, and was known as the Rock Crusher. This version was offered in high-performance big-block cars starting with the 1965 Corvette. The Turbo 350 transmission was prevalent in nearly all GM, rear-wheel-drive cars and trucks through 1984. Use the following information to compare physical description of your Chevrolet or GMC manual transmission in order to identify what model transmission is, MySpace !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs");
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