It usually begins with 18S101350 or 28N12950. Check whether there are any rings around the shaft splines. This is a 1967 3885010 case datedJune 2, 1967. Casting numbers are not GM part numbers. If you have a Muncie dated with a December build date it was actually built the previous year. The “A” stands for M20. Its quite common to see later cases replace early ones for this reason. This was mold pattern number 1. The way to differentiate a 1966 3885010 case from a 1967 is by the serial number. This a BRAND NEW SUPERCASE M22 4-Speed Muncie Rockcrusher Style Transmission. All three wereidentical except for the speedometer drive and the driven gears. Simply put, it is the number that is actually cast into the case when the molten aluminum is poured into the case mold. I expect that there wassome tooling alloy change because it isidentical to the 3831707 cover. The 3925661 casting seemed to surface by the last quarter of 1969. The side cover has seven bolts and two shift cams. I used bolt on shifter shafts instead of the stud type. Window and tanksticker resources reveal that therewas never an M21 option printed on asticker before 1966, even though manyM21s existed I believe the final-driveratio determined whether a close- orwide-ratio transmission was installed. This is mold number 1.Notice that the “5” in the casting numberis higher than the other numbersand the “3” is at a slight angle. The early M20 with the 24-tooth input only came in 10-spline. This could be an alloy improvement, a casting tool change, or some physical change. I guess I am looking for a Muncie transmission guide for dummies. PEND. Otherwise you can tell a difference by spinning the input while in first gear, and counting the revolutions of the input with respect to the output. We have identified the Muncie four-speed at a glance and have reviewed the transmission case numbers. Strut rod options and installing strut rods on 1963-’82 Corvettes. The Muncie 4-speed transmission was used from 1963-1974 on several different GM vehicles and engine types. 1964-81 GM 442 GTO GS MUNCIE M20 M21 M22 TRANSMISSION BELL HOUSING BOLT SET 14P. It is unique to the Muncie and was used until the very end of production in all main cases with the exception of the 3831704 case. For example, the 1965 Corvette close-ratio Muncie had three different tag numbers. This is Brian Higgins of the SK TrannyShop. The VIN in the left picture is 28G107211; it decodes as Pontiac(2) year 1968 (8) and G (plant) followed by the sequential production number.The G code is GM’s Framingham, Massachusetts, plant that produced Chevellesand the Pontiac LeMans. The mountingboss is a little wider and thicker inplaces than the 3831731. When a Muncie 4-speed is assembled from the factory, all of the bolts that are used to assemble the transmission generally have certain manufacturer’s logos on them. The 3884685 cover is a direct duplicateof the 3831707. FOR SALE! The number represents the month and the dots represent the week. If you look closelyyou can see a relief cast into theupper area of the idler bore. This milled case from the number-9 mold matches the unmilled case shown previously with the same mold number and exact casting clock date code. m20 m21 m22 '65-'74 4-speed manual transmissions:. Passenger side of the unrestored M22 transmission. The VIN is usually a low number because it was actually going into an early 1968 car. heavy duty max-load input bearing; fits muncie m20, m21, & m22 models from '65+ with 80mm o.d. The casting clock codes are at right above the fill plug. I know we will probably never find the original transmission but I would like to get the most correct transmission possible for the car. 68-72 GM A Body Hurst Shifter Muncie M-20 M21 M22 Transmission Shift Levers. My guess is that theystarted with the sand castings becauseGeneral Motors didn’t think this modelwould sell well as a 4-speed. The main case casting number was used for either a specific year or series of years. The 2.20:1 ratio is commonly designated as the Muncie M21 transmission. Muncie also had a second close-ratio transmission designated M22 and often referred to as the "rock-crusher," which was used behind the highest-performance engines and in Corvettes, the M22 is a highly sought-after performance transmission. (Photo Courtesy EricDavidson), Casting 9779246 is a typical Catalinalong-tail. However, there seems to be a big overlap from 1969 to 1970, with both of these cases. Therefore, this is a LeMans case. Even if your Muncie is assembled from a mix of parts, you should be able to determine the ratio. Muncies with 26-spline inputs and 32-spline output shafts came as M20, M21, and M22 transmissions. There is no point restampinga case unless you can do it right. By 1964 the 3851325 case appeared. heavy duty max-load. In this video I rebuild a Muncie M20 transmission.https://patreon.com/user?u=4693723#muncie #transmission #1970chevelle396 Because main cases are often swapped rather than being repaired, the best way to determine if you have an M20, M21, or M22 is to simply look at the gears. During prototype testing, this 7/8″ countergear pin was found to be the weak link in upgrading the Muncie transmission. This is a good example of a bad restamp (or fake). These are easy to adapt to a wide range of hot rods. Notice the other lettersand the type of options they represent.Because M21 is just a code, laterCorvettes or other 4-speed cars didn’thave Muncies; those equipped with aSuper T10 4-speed could have an M21or an M20 code. This is April 23, 1972, M21 ratio. Serial numbers for Muncie 4-speeds always begin with the letter “P,” which stands for Muncie Plant (not “passenger car.”) “M” and “N” were used to identify 3-speed Muncies; “O” identifies the Saginaw 3-speed with overdrive. By the start of 1969 these cases and all future cases had the drain plug boss drilled and threaded. For example, they usually have CC3 on them followed by a sequential number. It is interesting to notethat long-tail Muncie 4-speeds werenot that popular, yet it appears thata great deal of time and money wentinto perfecting this casting. Here are three rules that will help you determine which transmission you have: Muncie countergears had the same number of teeth on first-, second-, and third-speed sections. The Muncie 4-speeds (M20, M21, and M22) are some of the most popular manual transmissions ever made and continue to be incredibly popular. This onehas a January 19, 1967, date code. Muncie 4-Speed Transmissions: How To Rebuild & Modify. (Coincidentally, March 1965 seems to be a time when the 396 engine started to migrate into more vehicles, such as Z16 Chevelles, Corvettes, and full-size Impalas.) If you have to replace an early 7/8-inch case, a later casting is offered with the thick ears but machined for the early shaft. (Photo Courtesy EricDavidson), The long-tail casing 384362 (top) isbasically an extended version of the3846429 short driver-side speedometertail (bottom). Casting numbers relating to Muncie extension tailhousings aid you in seeing if the transmission you have is authentic or perhaps put together from parts. An example is P2D23B. I have changed out bulbs on other cars, but I can’t seem to find out how to get to the bulb on the C5 Corvette. It has a seven-digit serial numbercast into the case on the passenger’sside. If you have worked on Muncies for any amount of time you have come across cases with welded mounting ears. To confirm this simply look at the VIN. The 1967 and 1968 vehicles received a year, month, and day designator. These casting dates or “clocks” are not generally necessary to determine what type of Muncie you have. Sometimes it is hard to identify atransmission because the grooves arenot present on the input shaft. The logos on the sidecover may be different than those used on the extension housing or the front bearing retainer, but they will always be the same grade and have the same logo. They all seem to come from big-block cars. Some spots also have more material and the case has a thicker look to it. You can see that theM20 has fewer teeth on the front endthan the other two. $99.73 . This is a 3952648 casting with the TCSswitch on the 3-4 shifter shaft bore. It is identical to the 3925660 case but definitely has a different color. From 1967 to 1968, the serial number used year, month, and day designators; the month designator is now a letter. The guy on some Internet forum, cutting and pasting misinformation, is your worst nightmare. M20 input = 21 teeth. How can you tell if the transmission in your car is the one the car was originally built with? The reason for the overlap is simple. input bearing The 1965 case with the same casting number has a squared-off upper extension housing boss. The clock looks like a mathematical fraction with a 1/2-inch circle around it; they were a way to track any quality-control issues. The wiper systems in Tri-Five Chevys are ugly and prone to problems. Most transmissions are missing these tags, but if you want to do a complete restoration they are generally necessary. With the introduction of the 3885010 case, the countershaft bore was increased to 1 inch. These included a Muncie M22 "Rock Crusher" 4-speed manual transmission or M20 Hydramatic automatic. Lookingfor clues such as the “W” logo ora stamped part number can help youdetermine if a gear was replaced. If you don’t know what to look for it can be tricky to tell exactly which transmission you are looking at so here are a couple of methods to help you quickly recognize a Muncie. “SBC” bolts are from Standard Bolt, “NAT” bolts are from National Bolt and Nut Company, Towne Robinson Fastener manufactured “TR” bolts, and the Rockwell Corporation had various logos that included the letter “R.” Some other logos you might come across are “KS,” “RSC,” and “D.” Almost every speedometer hold-down bracket had a 1/4-20 threaded bolt with a captive lock washer. Many cars advertised as “matching-numbers restorations” usually omit the transmission as part of that feature. It’s identical tothe 3831704, except it had a biggerfront bearing bore. Casting 384362 is the long-tail versionwith a driver-side speedo. However, there were several design upgrades and modifications made during the total production run. They often get angry because they don’t want to face up to the fact that they got burned and made a bad 4-speed purchase. This is for a 1968 production car. This might have been a different alloy because its appearance is identical to the 3851325 case and it was to be used strictly with the new big-block 396 engine. So you can tell the difference by counting the teeth on the input or the cluster gear that engages the input. Almost gone. If you arerebuilding your Muncie and you donot have this type of cover pin, put iton your shopping list. This is the first version of the 3831752cast midplate. Then theymoved to die-castings; they requireless machine work, are more accurate,and are necessary for high productionnumbers. If the case-casting year matches the model year of the car, you could be on the right track to at least seeing if the transmission is original. In case you discover an M22, you might have the last word Muncie designed for the excessive torque of a big-block that may bolt to your small-block. The left case is a 1963 T-10. Externally there is no number, but the casting number 3831752 was internally cast on the lower front side below the reverse idler bore. For close to eight decades, the company has produced quality power components and systems like the Muncie 4-speed transmissions (M20, M21 and M22).It’s easily one of the most popular manual transmissions on the market. This means the Muncie was assembled December 13, 1967, for the 1968 model year. Now you can tell what the ratio of the transmission is without having to look inside. I spent a great deal of time sorting through their parts. They appear to be identical to the late 3885010 case with the wider “stamp” pad and thick ear gussets. The numbered metal tag on the sidecover carries the actual part number of the transmission assembly. The casting number depends on the date the service case was installed. It is a date code for when the transmission was assembled based on the model year, not calendar year. C $1,264.73. An M-22 "Rock Crusher" has no rings, so if you see rings in your transmission, it means it is not an M-22 "Rock Crusher." Muncie Transmission ID and Ratio Guide. This particular transmission is going into a Jaguar E-type! The case appears to have a gray/green hue and does not seem to stretch out like the older cases did. The case appears to be identical to a 3851325 case so perhaps it is made of a different aluminum alloy. Muncie M20 M21 M22 T10 Transmission Torque Lock Slider T10-15 (304641) $17.50 + shipping. Some of the best Muncie builders participate on that page. It was used primarily with the 26-spline input shaft and larger 32-spline output-shaft models, so it appears that they were looking to optimize strength everywhere possible since the 454 engine was introduced in 1970. Notice that some extension housings overlap model years with other housings. (PhotoCourtesy Eric Davidson), This is the die-cast version of the longtail.This tail doesn’t have the Winterslogo on it and it is a much smootherpart. People often get confused about what a casting number is. We will also go over how to read the date codes. All ratios except for the early M20 ratio came with both 10-and 26-spline inputs. You would think that in nectors. The “661” is considered the strongest factory GM case. By late 1963 the rare 3839606 case started to show up in cars with a larger bearing bore. It is easy to determine an early Muncie four-speed transmission side cover from the later models by the way the transmission shifter arms are attached. Next time we will go over the input shaft and output shaft splines, rings or grooves that may exist around the input shaft splines. (Photo CourtesyEric Davidson). The evolution of case design also helps pinpoint the year a case was released. A “4” next to the casting is the mold pattern number. And you’re right, Zack, not too many people actually know how to distinguish a Muncie four-speed transmission from a Saginaw or BorgWarner, or even what type of Muncie four-speed they have. Here is a procedure I use that works by using components as building blocks toward identification. The 2.56:1 ratio is commonly referred to as the M20. muncie. Vette. input bearing. Muncie / Four speed conversion , Hurst shifter rebuild , Differential carrier and gear change. This is the standard Muncie 4-speedcase. Holley’s Sniper Kit Offers Easy EFI Fuel Pump Conversion, Installing Strut Rods on 1963-’82 Corvettes, Fixing Anti-Lock Brake Electrical System on 2001-2004 Corvettes, Corvette Wiring Gremlins Solved and Charging System Upgrade, Patent Pending, 7/8" Bore Mostly Used In 1964, Patent Number, 7/8" Bore, last 3 Digits Milled Off Of Case, Thin Fin Tailshaft, Driver-Side-Mounted Speedometer, 27 Spline, Thick Web Tailshaft, Driver-Side-Mounted Speedometer, 27 Spline, Pontiac Catalina Long Tailshaft, Side-Mounted-Speedometer, 27 Spline, Passenger-Side-Mounted Speedometer, 27 Spline, Passenger-Side-Mounted Speedometer, 32 Spline, 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. This one wascast in the fourth week of January1974 in mold number 15. difference between the (M20,M21) and the M22 transmission, you can not really tell by looking at the case,the difference is the actual cut of the gears,you can see this in the picture below, the M20 and M21 have a much greater angle to the teeth of the gear and also will have a twist in the teeth (helical bend), the M22 gear … It appears that more milled cases are in circulation compared to unmilled cases. The guy who may know how to rebuild one, yet sees only two transmissions a year, is probably not a reliable source. This should get you started. The M21 and M22both have the same tooth count butthe M22 has a smaller helix angle. Without removing the … It has anAugust 7, 1974, build date. The headset-driven gear is the countergear front gear with a tooth count of 25. Notice their circled “W”logo. This cover has the better hat-stylepivot pin. The 3839609 main case was usedduring 1963 and 1964. Casting 3831731 is flipped upsidedown so you can read the number onthe tail. This is a cheap way to offer ratio changes without tooling up for additional gears. PEND.” cast above “General Motors Corp.” Notice that the drain plug boss was not drilled out. It’s still a good habit to double-check the gears to confirm the ratio because often the ratios were switched around. In fact, we bought a BorgWarner transmission by mistake. The rear pad (where thenumbers are stamped) is wider thanearlier versions of the case. Casting 3857584 is pretty muchidentical to the wide-fin 3846429tail. You can think of them as a system of checks and balances. Notice the lower “thin” fin. Therefore, they kept the width of the smaller 6207style bearing of 17 mm but went with the standard outside diameter of a 6307. SHARE THIS ARTICLE: Please feel free to share this article on Facebook, in Forums, or with any Clubs you participate in. These transmissions probably were assembled with special alloy gears, because the case casting is identical to the 3851325 as well. The 2.56:1 ratio is referred to as the M20. Because the Muncie was really GM’s design improvement of the T10, the 7/8-inch-diameter counter-shaft was also used in 1963. By late 1964 the 3851325 case was cast with GM Patent Number 3088336. Is there an easy way to tell which transmission we should be looking for? And you're right, Zack, not too many people actually know how to distinguish a Muncie four-speed transmission from a Saginaw or BorgWarner, or even what type of Muncie four-speed they have. The 1964 through 1968 Muncie side covers had a stud coming out of the side cover that the shift arms attached to using a nut. Usually when an external modification is made to the case, such as milling, it means a special internal mod. The 3864848 case, with a December 17, 1964, build date, was probably for an early 1965 car. I learned from speaking to many builders that the rare 3864848 case seems to be in a few Corvettes and full-size GM cars with big-block engines. MUNCIE 4 SPEED Transmission M20 M21 M22 Rebuild DVD DIRECT FROM AUTHOR - $29.16. The M20 & 21 have a 7/8", M22 is 1". It duplicatesthe short extension mounting andshifter locations. (Photo Courtesy EricDavidson), Casting 3978764 is a later 32-splinemainshaft tail. Casting 3846429 is a thin-fin versionof the 3846429 casting. For example, the serial number P8A01 is January 1, 1968. 1969, only M22 transmissions had drain plugs. Transmissions are an essential part of hot rod builds. A CT3 is a replacement transmission. Most of thesecastings look very rough. A gear ratio is a combination of two ratios multiplied together. Serial numbers from 1963 to 1966 included only the month and day. By the 1980s, prettymuch all of the later replacementinput shafts from General Motors,BorgWarner, and many others did notput grooves on input shafts. Muncie 4-speeds pretty much have a solid chronological order regarding the main case, retainer, midplate, and extension housing casting numbers. Because date-coded serial numbers and VINs were only stamped (not cast) into the main case, the main case should be your starting point. The bearingbore is smaller than the Munciecase on the right. The only real difference between the M21 and M22 structurally is the countershaft size. Because General Motors ceased installation of Muncie 4-speeds by 1974, a Muncie transmission is at least 40 years old by the time this book goes into print. This is called a narrow 6307 bearing (PN N307LOE). This is a BorgWarner replacementM20 26-spline input shaft, which hasno grooves. The M21 & M22 is a Muncie engineering design, this transmission is aluminum case, extension housing and side cover. This is a 1970 M20 case. Every first gear has 36 teeth, second gear has 30 teeth, and third gear has 27 teeth. I have done my own research by looking at literally thousands of cases, extensions, and sidecovers to draw my own conclusions. Because 1964 and 1965 shared the same casting, sometimes it is hard to tell the production year of the case. It was installed in the Camaro, Chevelle, Buick GS, Pontiac GTO, Olds Cutlass, and many other classic cars. These cases were obviously repaired but sometimes a replacement case was the only fix. These cases were run in conjunction with the 3851325 case. Of course, every company has a unique logo on its bolts. GM TURBO 350 TRANSMISSIONS: HOW TO REBUILD AND MODIFY, How to Correctly Select Wheels and Tires for Chevy and GM, The Complete Cylinder Head Guide for Chevy Small Block Engines, Roller Cams Guide for Small-Block Chevys: How-To, Tips & Techniques, Chevelle Performance Projects: Engine Upgrade Guide, How to Build Big-Inch Chevy Small-Blocks: Valvetrains Guide, Bodywork Guide for C2 Corvette Restoration – Step by Step, GM Automatic Overdrive Transmissions Shift Kit Guide, Intro to Small-Block Chevy Cams and Valvetrains, C5 Corvette Builders Guide – Wheels and Tires (Part 4), Chevy Big-Block Performance: Camshaft and Valvetrain Events. Muncie Transmission information D & L Transmission To order call 1-631-351-4837. Many rebuilders have bins full of tags.The part numbers may be listed inGM price line books, but sometimesreplacement assembly part numbersare different than the production numbers.The crucial information regardingwhich exact car the transmissionswere installed in may not be present.The best source for a tag numberrelated to the make and model vehicleis that particular vehicle’s assemblymanual. Just three types of Muncie 4-speeds are available based on the RPO (regular production option) code used when a car was ordered: the M20 (standard wide-ratio), M21 (close-ratio), and M22 (heavy-duty close-ratio). case. The VIN ishard to read. These are usually the firstnumbers used to start the identificationprocess. Serial numbers are stamped into the case. GM Muncie M20 M21 M22 4 Speed Transmission Torque Lock Slider Sleeve WT297-15. If you liked this article you will LOVE the full book. $22.68 + shipping. The fact is General Motors couldn’t use a standard 6307-style bearing with a width of 21 mm because the gears were already tooled and made. This is a typical 3831707 cast cover. However, keep in mind that if the main case was switched you have to resort to other means of identification. And you’re right, Zack, not … You would think that in1969 they would have just sold youan upgraded 1966-and-up Muncie asa replacement. As mentioned previously, we know that the Muncie came with several ratios. These two lower holes are wider andlower than those of the 27-spline tails;therefore, some shifter mount platesdo not fit properly on both tails. ... muncie m20 m21 m22 transmission 1-2 synchro assembly with rings springs keys (wt297-80a) tpd pro-line. (Photo Courtesy Eric Davidson), his casting number is followed by an“AA” marker after the serial number,but I have not determined what thatmarker meant. Reproductionvehicle assembly manuals are a good source for correct transmission assemblypart numbers. The T10 front bearing size was reduced in diameter in 1963 only. James Beery details how to reset the window indexing feature on 2005-'17 Corvettes after the battery dies. The 2.20:1 ratio first gear is usually referred to as the Muncie M21 transmission; based on GM's production codes. As a mold is poured, date-coded clocks are cast into most cases that represent the month, week, and sometimes day the case was cast. The “T” stands for December and 13 is the day. 00:00. These two milled 3864 cases have March 1965 assembly dates. Noticethe odd casting clock above the fillplug and that it was drilled for a drainplug. 1964-81 GM 442 GTO GS MUNCIE M20 M21 M22 TRANSMISSION BELL HOUSING BOLT SET 14P. Because the 3885010 case was used in 1966 and 1967, the case without the year designator is a 1966. The case countershaft bore usually stretched out so the increase in shaft diameter spread the counter-shaft load over a wider area. - Day Two Build Recap, Week To Wicked: 1955 Chevy – Day One Build Recap, We Test Four Different Ratio Saginaw Power Steering Boxes. Find great deals on eBay for m22 muncie transmission. The 3831704 caseused the same bore as the 1963 T10. The replacement case (GM PN 3925659) was used for all 1966– 1974 Muncies as listed in the GM AC DELCO 1978 service parts manual. The basic appearance, design and operation of the Muncie four-speed did not change much during the period when the transmission was used in GM production cars. Changing the oil on these transmissions can be tricky, as the oil-fill port is on the side of the transmission. Click the button below and we will send you an exclusive deal on this book. Free shipping. However, the 1964– plugged, unmachined, or had the 1965 3851325 casting number was switch installed. $78.77 $72.77 $99.95. - Day Four Build Recap, Week To Wicked: Two Days Left To Build our 1955 Chevy! This is the second generation of platecasting 3831752. (A serial number is stamped into the case by hand, usually with numbered and lettered punches.) Most of the books and articles I have seen, combined with some bits of Internet folklore, tend to have the same flaws because most information is copied and simply edited and resubmitted. cally, some covers were issued with The case has several unusual fea­stud-type shifter shafts and oth-tures. The “ID” groove system was good until several things changed. Chevy Muscle Car Tech Tips, Guides, Articles & How-To. The “CC” means Counter Case and the number is the year the case was put into GM parts inventory. All ball bearings have standardized numbers used by the bearing industry. The early “3851325 PAT. The countergear has 17 teeth on its first-gear section driving the actual first-speed gear with 36 teeth. Seller 99.6% positive. These guys stockpiled a lot of parts!