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. Muncie Transmission information D & L Transmission To order call 1-631-351-4837. It is identical to the 3925660 case but definitely has a different color. Muncie 4-speeds pretty much have a solid chronological order regarding the main case, retainer, midplate, and extension housing casting numbers. 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. Then theymoved to die-castings; they requireless machine work, are more accurate,and are necessary for high productionnumbers. I’ve met many of these rebuilders and have had the pleasure to create great friendships with them. The replacement case (GM PN 3925659) was used for all 1966– 1974 Muncies as listed in the GM AC DELCO 1978 service parts manual. $99.73 . Q: Hello, my name is Zack. 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. As mentioned previously, we know that the Muncie came with several ratios. We recently went to a local swap meet but our problem is that all of the four-speed transmissions look the same. The 1963 transmission had a smaller front input shaft bearing and a specific front bearing retainer with a smaller outside diameter than the Muncie transmissions from 1964 and up. They all seem to come from big-block cars. Tooling up for a die casting isvery expensive. Muncie also had a second close-ratio transmission coded M22 and known as the "rock crusher," which was used behind performance big-block engines and in some Corvettes. The only Muncie I ever blew up ( except for syncros) was an M22-go figure. 00:00. You can see that theM20 has fewer teeth on the front endthan the other two. Free shipping. 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. Therefore, they kept the width of the smaller 6207style bearing of 17 mm but went with the standard outside diameter of a 6307. It only has one boltpattern for the shifter. Simply put, it is the number that is actually cast into the case when the molten aluminum is poured into the case mold. (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.) A reader sends in a question about fixing the anti-lock brake electrical system for 2001-2004 Corvettes. - Day Two Build Recap, Week To Wicked: 1955 Chevy – Day One Build Recap, We Test Four Different Ratio Saginaw Power Steering Boxes. $21.00 + shipping. This usually indicates that the gears used in the milled cases might be of a different steel alloy. (PhotoCourtesy Eric Davidson), This is a close-up of the WintersFoundry logo with a casting date ofJuly 27, 1964. During prototype testing, this 7/8″ countergear pin was found to be the weak link in upgrading the Muncie transmission. These cases were obviously repaired but sometimes a replacement case was the only fix. Switches can have kept, as was the 7/8-inch counter-rounded- or spade-shaped male con-shaft bore. We road-test four different Saginaw power steering boxes and report on which one was best for autocross and which was best for street driving. ... muncie m20 m21 m22 transmission 1-2 synchro assembly with rings springs keys (wt297-80a) tpd pro-line. By changing the ratio of just the head set (input shaft and front of the countergear) you can change the overall ratio. Most of thesecastings look very rough. The progression of the 10-spline input identification groove system. 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. Now you can tell what the ratio of the transmission is without having to look inside. The casting clock codes are at right above the fill plug. Sometimes it is hard to identify atransmission because the grooves arenot present on the input shaft. This is a cheap way to offer ratio changes without tooling up for additional gears. 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. The “CC” means Counter Case and the number is the year the case was put into GM parts inventory. These transmissions probably were assembled with special alloy gears, because the case casting is identical to the 3851325 as well. By late 1964 the 3851325 case was cast with GM Patent Number 3088336. Passenger side of the unrestored M22 transmission. 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. Muncie M20, M21 18 tooth front idler. 80mm outside diameter . In fact all of the upper-speed gears have the same tooth count regardless of ratios. The 3831704 caseused the same bore as the 1963 T10. While vehicles with an axle ratio of 3.55 and lower usually used a wide-ratio transmission. Here are some 26-spline input shafts.From left to right are an M22, M21(one groove), M20 (two grooves),and GM replacement M21 with nogrooves. This could be an alloy improvement, a casting tool change, or some physical change. This cover has the better hat-stylepivot pin. If your bolt logos match and your front retainer locking tabs are in place it usually is a good indicator that the transmission has never been taken apart. The 2.20:1 ratio is commonly designated as the Muncie M21 transmission. The “661” is considered the strongest factory GM case. Casting 384362 is the long-tail versionwith a driver-side speedo. This is a 1970 M20 case. The wiper systems in Tri-Five Chevys are ugly and prone to problems. This is a good example of a bad restamp (or fake). This is a typical 3831707 cast cover. Each new Auto Gear transmission is built from genuine Auto Gear parts, the highest quality available. The number represents the month and the dots represent the week. (Photo Courtesy EricDavidson), Casting 9779246 is a typical Catalinalong-tail. Let’s take a look at how the Muncie main case evolved from 1963 to actually going into an early 1968 car. 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. Noticethe odd casting clock above the fillplug and that it was drilled for a drainplug. Muncie M22 18 tooth front idler WT 297-10B. 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. Strut rod options and installing strut rods on 1963-’82 Corvettes. $78.77 $72.77 $99.95. 1966 -74 NOS USA MUNCIE SYNCHRONIZER RINGS M20 M21 M22 TRANSMISSION. PEND.” cast above “General Motors Corp.” Notice that the drain plug boss was not drilled out. The headset-driven gear is the countergear front gear with a tooth count of 25. Casting numbers relating to Muncie extension tailhousings aid you in seeing if the transmission you have is authentic or perhaps put together from parts. A CT3 is a replacement transmission. The casting number for the midplate never changed. Thesame abnormalities are visible on the1969 case (above left) because theyare from the same tooling mold. By late 1965, the 396 Turbo Jet engine, rated at 425 hp, was introduced. This is the first version of the 3831752cast midplate. (Photo CourtesyEric Davidson). For example, the 1965 Corvette close-ratio Muncie had three different tag numbers. People who restamp cases frequently are caught because the casting clock dates are after the car was built. Several things are needed to identify a Muncie four-speed transmission correctly. Shop with confidence. Of course, every company has a unique logo on its bolts. What you can see is that before March 1965 these cases were not milled. Later cases seem to only have one clock. Seller 99.6% positive. Muncie Front Idler M20 M21 M22 . From 1969 to 1974 all-ratio Muncies came with drain plugs. This particular transmission is going into a Jaguar E-type! 1964 GM Chevy Muncie M20 4 Speed Transmission chevrolet #16. Ithas the early non-hat-style pivot pin. $22.68 + shipping. However, there were several design upgrades and modifications made during the total production run. Many owners … An example is P2D23B. ... How to Tell if Your Corvette Has Matching Numbers. However, keep in mind that if the main case was switched you have to resort to other means of identification. 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. All ball bearings have standardized numbers used by the bearing industry. (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. The 1969–1974 Muncies received a ratio designator at the end of the serial number: “A” for M20, “B” for M21, “C” for M22. Almost gone. The case countershaft bore usually stretched out so the increase in shaft diameter spread the counter-shaft load over a wider area. The M22 X ratio 4 speed fills that much needed requirement. There are several interesting features which are special in the 1965 M22. I have an M21 in my ZZ4 powered '65 Camino and love it. Some of the best Muncie builders participate on that page. This is for a 1968 production car. Muncies with 26-spline inputs and 32-spline output shafts came as M20, M21, and M22 transmissions. The last Muncie case was the 3925661. It’s still a good habit to double-check the gears to confirm the ratio because often the ratios were switched around. An example is the date code P8T13. 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. Usually a casting number is changed because of a design change. 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. You can think of them as a system of checks and balances. If you liked this article you will LOVE the full book. The “T” stands for December and 13 is the day. The Muncie 4-speeds (M20, M21, and M22) are some of the most popular manual transmissions ever made and continue to be incredibly popular. Noticethat the serial number has been ground off (left). 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." Casting 3846429 is a wide-fin casting.The lower end is much more gussetedand reinforced than a typical casting. The early “3851325 PAT. Remember, if the transmission is still in the car only the 1969 to 1974 cases had ratio identifiers in the serial number. The 1967 and 1968 vehicles received a year, month, and day designator. Muncie takes its name from its home headquarters in Indiana. Seller 99.2% positive. To confirm this simply look at the VIN. Transmissions are an essential part of hot rod builds. This is a page from an old factory 1967 Nova assembly manual showing threedifferent part numbers for the M20 and one number for the M21. 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. Some cases may look identical and have a different casting number but have the same GM part number. Notice their circled “W”logo. It is driven by the input shaft with 21 teeth. This was eliminated after 1963. Look for the "GM" sign imprinted on the transmission box to identify the manufacturer of the transmission. 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 … The Muncie was the top high-performance manual transmission General Motors offered in its muscle cars of the 1960s and early 1970s. The mountingears also have thicker gussetsthan earlier cases. Perhaps an alloy change as well as a tooling change warranted a new number. These are easy to adapt to a wide range of hot rods. Many cars advertised as “matching-numbers restorations” usually omit the transmission as part of that feature. 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). A very small number of 396 engines also found their way into the 1965 Impala. Muncie Transmission ID and Ratio Guide. Date code format for 1963–1966 model years was just a month and day. Muncie four-speeds were produced in two different ratios: the wide ratio (M20) and the close-ratio (M21). Zack, thanks for the letter and I am sure you and your father will have the car ready for your prom. The choice of transmission usually was determined by the engine size and rear axle ratio. 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. This is the second generation of platecasting 3831752. An axle ratio of 3.73 and higher usually came with a close-ratio transmission. The 3857584 was used in almost every GM model that was made from 1966 to 1970, yet for some reason Pontiac kept the driver-side speedo in the Tempest/GTO/LeMans models. From left to right, early M20, M21, later M20, and M22. Find great deals on eBay for m22 muncie transmission. Casting 3857584 is pretty muchidentical to the wide-fin 3846429tail. I … Notice the lower “thin” fin. It was installed in the Camaro, Chevelle, Buick GS, Pontiac GTO, Olds Cutlass, and many other classic cars. (A serial number is stamped into the case by hand, usually with numbered and lettered punches.) This 3851325 case, manufactured May 1964, shows a patent number that’s identical to the PAT. The seven bolts on the sidecover have the same logo. 1974. The 3884685 cover is a direct duplicateof the 3831707. Is there an easy way to tell which transmission we should be looking for? WT297-10. At a quick glance the Muncie can be easily distinguished from the Saginaw since the reverse lever on the Muncie is mounted on the extension housing of the transmission, whereas on the Saginaw transmission the reverse lever is mounted in the side cover of the transmission. Some spots also have more material and the case has a thicker look to it. For example, P0101 indicates January 1. The M21 & M22 is a four speed, RWD or 4WD transmission. These guys stockpiled a lot of parts! This is called a narrow 6307 bearing (PN N307LOE). m20 m21 m22 '65-'74 4-speed manual transmissions:. The 1965 case with the same casting number has a squared-off upper extension housing boss. Their number was 41307B. We replace the engine wiring harness and upgrade to a Powermaster one-wire alternator on our 1964 Corvette project car. - Day Five Build Recap, Week To Wicked: Will We Finish? Popular . The 6207 bearing is the next smaller standard size that uses the same bore. shipping: + C $213.95 shipping . heavy duty max-load. “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 people become so focused on price comparisons when purchasing a “rebuilt” Muncie that they frequently overlook what was actually done to the transmission and, more important, who did the work. Untouched “survivor” Muncies are rare; so are the ones that have correct correlating casting and serial numbers. I can guarantee that most people reading this book will never see some of the items I’ve stumbled across. 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. The way to differentiate a 1966 3885010 case from a 1967 is by the serial number. This page is in place to support this book and it’s free. It has anAugust 7, 1974, build date. Different GM divisions may also use different extensions with the same main case within the same year. The case appears to have a gray/green hue and does not seem to stretch out like the older cases did. 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. 1969, only M22 transmissions had drain plugs. Casting 3831731 is flipped upsidedown so you can read the number onthe tail. James Beery details how to reset the window indexing feature on 2005-'17 Corvettes after the battery dies. 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. 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 1964 through 1968 Muncie side covers had a stud coming out of the side cover that the shift arms attached to using a nut. You can copy and paste this link to share: https://www.chevydiy.com/muncie-4-speed-identification-guide/. Almost gone. M21 input = 26 teeth. Its quite common to see later cases replace early ones for this reason. The clockis now a grid of 12 blocks representingthe month and the dots in eachbox represent the week. There is no point restampinga case unless you can do it right. This one is very rare. This is on a 66 to 74 model year Muncie. 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. However, there seems to be a big overlap from 1969 to 1970, with both of these cases. However, the 1964–1965 3851325 casting number waskept, as was the 7/8-inch countershaftbore. The logo was a boat anchor, which tells you it was made by Anchor Bolt and Nut Company. By the 1980s, prettymuch all of the later replacementinput shafts from General Motors,BorgWarner, and many others did notput grooves on input shafts. Because date-coded serial numbers and VINs were only stamped (not cast) into the main case, the main case should be your starting point. This is a 3925661 case from a 1974Corvette M20 transmission. A Muncie differs from a Saginaw transmission in that its reverse lever is in the tail housing, not the side cover. 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. 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. To fix these issues we install a modern system from Raingear. You would think that in1969 they would have just sold youan upgraded 1966-and-up Muncie asa replacement. So how did the ratios change? This is what makes the car hobby so great. This 1968 3925660 main case has a P8R04 assembly date and was cast in anumber-2 mold. It has a seven-digit serial numbercast into the case on the passenger’sside. Without removing the sidecover you can look at the input shaft and check for identification grooves cut into the spline. GM Muncie M20 M21 M22 4 Speed Transmission Torque Lock Slider Sleeve WT297-15. These surface fromtime to time but are rare. This early type is onlyfound in 1963 transmissions. Serial numbers are stamped into the case. If you have a Muncie dated with a December build date it was actually built the previous year. 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. With the introduction of the 3885010 case, the countershaft bore was increased to 1 inch. 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. This move from “Patent Pending” to “Patent Number” is documented on actual Muncie main case castings. All documented M22 transmissions have the #3925660 maincase. Next time we will go over the input shaft and output shaft splines, rings or grooves that may exist around the input shaft splines. It was a 3925661 casting. input bearing The mathematical formula for determining a gear ratio in these transmissions is: Let’s use the late M20 and plug the tooth counts into the above formula. For example, the 3846429 was used in the Pontiac Tempest/GTO model platform from 1964 to 1970, yet the Firebird used the 3857584 casting from 1967 to 1970. These early long tailswere sand-cast. add to cart. 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. Tailhousings often get damaged where the reverse shifter shaft lock pin sits, and at both the shifter and main mount bolt-boss locations. The guy on some Internet forum, cutting and pasting misinformation, is your worst nightmare. The M21 & M22 is a Muncie engineering design, this transmission is aluminum case, extension housing and side cover. The Muncie was used with most performance General Motors engines. The 2.20:1 ratio first gear is usually referred to as the Muncie M21 transmission; based on GM's production codes. The left case is a 1963 T-10. We have identified the Muncie four-speed at a glance and have reviewed the transmission case numbers. “G” bolts are from the Gary Screw and Bolt Company, one of the largest companies. 1. The reason for the overlap is simple. The Muncie transmission was an aluminum main case/extension housing, side-loaded transmission with a side-lever shift linkage. This is Brian Higgins of the SK TrannyShop. The 1969 and later model side covers had a hole in the side cover that the shift arms attached to using a bolt. Most of the time the other cloc is blank, but occasionally it represents numbers and deviations to the original blueprint.