Just like certain engines have earned great reputations over time, some transmissions have transcended their yeoman’s duties to become legendary, desirable, and mythical in their own right. We’ve compiled a list of what we think are the Top 11 factory transmissions ever offered in American cars. This list could have easily stretched out to twice or three times that, especially if we decided to include big truck transmissions like the Mack Quadruplex, the Road Ranger, and others.
As usual, there are some notable omissions from this list. You aren’t going to see the Powerglide on this list because although it is the most popular drag racing transmission used in dragsters and high horsepower door slammers today, in factory form, it wasn’t known as a high performance unit aside from the few that were installed into 409ci equipped Chevy models in the 1962/63 time frame. The T5 isn’t on the list either, nor is the T-10 or Super T-10. Hey, who just threw that planetary gear set at us?!
Here’s our list (in no specific order) of the Top 11 Best Factory Transmissions Ever Offered in American Cars
11.) The Chrysler A727 Torqueflite – The Torqueflite line was born in 1956 and has been produced in dozens of different variants over the years. For the purposes of this list, we’ll concentrate on the most well known version of the transmission in the world of muscle cars and high powered trucks, the 727 Torqueflite. Used from 1962-1991 in an amazing array of vehicles, the ‘Flite had an aluminum case and was more than 50lbs lighter than the A488 transmission it replaced, it was way stronger. Easy to fix, easy to beef up, and still basically growing on trees, the 727 Torqueflite remains a top shelf automatic transmissions in street machines today. It lived behind big blocks, small blocks, Hemis, and factory drag cars of all stripes back in the day and soldiers on to the present.
10.) The Allison 1000 – The biggest power war in the modern world of the OEMs has come on the diesel pickup truck front. What started off as a scene for guys who wanted to pull big trailers has evolved into the modern equivalent of the 1960s yearly horsepower escalations that the big three engaged in to whip up sales. While the diesel engines themselves are impressive with their 400+hp and 600+ lb/ft of torque in factory form, the transmissions are equally impressive because they have to handle all of that power! Introduced in 2001 along with the Duramax diesel engine in GM trucks, the Allison 1000 is a monster 330lb piece that now packs six gears and the ability to handle a RATED 750 lb/ft of torque. The transmissions itself is larger than lots of engines used in cars today and it has to be to handle all that torque. Diesel enthusiasts have been pounding these units with far more than the recommended levels of power for years and other pieces of the driveline normally fail before the mighty Allison. This is BY FAR the heaviest duty factory issued transmission on the list.
9.) The Ford Toploader – In the realm of indestructible four speed manual transmissions, the legendary Ford Toploader certainly sits in some rare air. From 1964 right on through 1973, it was the transmission that lived behind everything from high winding 302ci small blocks through the thundering 427, 429, and 429ci big blocks. The trans could be found in racing applications from off road trucks to the drags and on the road courses as well. More than 100 Ford models had Toploader 3 and 4-speeds installed in them through the production run. The Toploader was so named because the removable access plate to service the unit was located on top instead of on the side like most other manuals. This was one of the reasons for the Toploader’s strength as the top mounted plate made the case lots more rigid than side mounted plates. If you are looking for one at the swap meet, count the number of bolts on top retaining the plate. If there are 10 bolts you have a four speed. If there are nine you have a three speed.
8.) The GM Hydramatic – GM’s first automatic transmission, and the first truly mass produced automatic transmission for cars was developed by Cadillac and Oldsmobile in the 1930s, first was optional equipment in 1940, and remained in production until 1967. It was the first automatic transmission hot rodded for drag racing and it was so advanced for its day that by the early 1950s, companies like Hudson, Nash, Willys, Lincoln and even English luxo brands Bentley and Rolls Royce were buying them from GM to use in their own cars. The original Hydramatic transmissions were in production until 1967 with millions upon millions produced through the run. It made its way onto this list because it was factory equipment not just in cars but also in tanks. That’s right, the M5 Stuart and M24 Chaffee tanks used these transmissions. The Stuart was powered by a pair of Caddy V8s, each of which had a Hydramatic bolted to it. That’s bad ass, boys and girls. Another interesting factoid is that these were four speed transmissions. They did not have an overdrive as fourth gear was 1:1. Hydramatics also did not use a torque converter that multiplied engine torque, instead a basic fluid coupling was used.
7.) The Chrysler A-833 – By many accounts, the Chrysler A-833 four speed was born out of desperation in the early 1960s when Chrysler’s attempt at backing their highest performance cars with a Borg Warner T-10 failed badly. While Mopars equipped with automatic transmission were eating the world alive on the strip, the stick cars were stuck with a three speed box and were not cutting the mustard to the standard the factory wanted. The A-833 was a clean sheet design and stands as one of the most successful four speeds in automotive history. First available in 1964 model year cars, they would continue to be made (in a couple different versions) deep into the 1980s. Because they were born with performance in mind, they were built like anvils. Cast iron cases were it until the 1970s when weight reduction and fuel economy became hot button issues. Laid up against other four speeds of the era, the A-833 is larger and heavier by a lot, but it can be argued that they were the strongest crash boxes of their time. One of these and a Dana 60 are the stuff gear bangin’ dreams are made of. Through the years, most of the internal revisions made to the A-833 were for better performance and hard driving. Their were a few different gear sets available over the years and through some research we learned that in 1965 the shift fork was redesigned for better 1-2 power shifting (seriously!), the cut of internal gears was modified for street Hemi models, and syncho rings were upgraded, again to survive wanton abuse and hard driving. If you are yard shopping or swap meet browsing, you want an iron case unit. They are vastly superior to the weaker aluminum case and less performance oriented models of the later 1970s and 1980s.
6.) The SM420 – Strength has been one of the primary attributes of many transmissions on this list but few of them have it in such raw brutality as is exhibited in the SM420. This 137lb, 10.7″ long wonder is a physical example of the gearhead term, “bombproof”. Introduced as a heavy duty truck transmission in 1947, it was produced until 1967 for civilian use and into the early 1980s in military applications. With a non-synchronized first gear sporting a 7.05 ratio, off road guys love these for crawling applications. The transmission is a top loader style and the shifter also heads straight into the unit. There are no external shift rods or any exposed moving parts, pieces, or linkage. In 20 years of major production, no significant changes were made to the SM420. Yeah, there were some upgrades internally, like the use of neoprene seals, but this thing was a tough enough bastard when it hit the streets that it didn’t need major changes. The SM420 is not a high performance transmission in the normal BangShift sense, but having owned a couple of trucks equipped with these babies now, we love them. The throws are long, they hate the cold, they normally live in stuff that runs out of breath at about 60mph and they’re basically the manual transmission equivalent of a grizzled, tough-ass old man. What’s not to like about that?
5.) The Ford C6 – While the C4 was produced in larger numbers, the C6 was designed to handle the grunt of the biggest and most powerful Ford engines of the 1970s and has continued to exist, albeit in modified forms into modern times behind diesel trucks and other heavy duty applications. The C6 was rolled out in 1966 as a replacement for Ford’s MX transmission which engineers wanted to improve upon. The typical engineering goals were in play. The new transmission needed to be lighter, simpler, and stronger, capable of handling the increased power output of engines in the middle 1960s and ultimately had to be robust enough to serve the company for the foreseeable future without a redesign. In many ways the C6 was a scaled up C4 although it was the first automatic transmission to use the Borg-Warner flexible shift band which was supposed to increase durability and service life. The C6 used the same ratios as the C4 transmission. We picked the C6 for this list because it was the auto trans that handled the Boss 351 Mustangs, Cobra Jets, full sized cars with 427, 428, 429, and 460 engines along with trucks backing big block FE and 385 series power. In the land of BS, bigger and stronger is better!
4.) The TH425 – The only front wheel drive transmission on the list has to be the beefiest and most robust ever built. The TH425 was constructed with the intention of living behind big 455ci and 500ci engines in Oldsmobiles and Cadillacs. It also found its way into GM constructed motorhomes during the production run of 1966-1978 as well. Engineers at GM took the already battle proved TH400, changed the direction that it rotated, added a big ass chain drive, and made it look creepy to fit the packaging constraints of a big block, front wheel drive car, and voila! A legend was born. The chain that GM used was essentially a timing chain on steroids as it is at least twice the width (maybe three times?) of the normal factory link style timing chain. The TH425 is on the list because it is kind of a freak show and it was a creative engineering solution for a problem using mostly off the shelf parts.
3.) The Muncie M22 Rockcrusher – No four speed of the muscle car era has more of an aura around it than the Muncie M22, known by enthusiasts as the fabled, “rockcrusher”. The name came from the fact that the transmission is equipped with gears that are cut much straighter (not totally straight cut though) than normal, producing an industrial sounding whine that us knuckle dragging gearheads hear as a symphony. What many people fail to realize is that the M22 was not designed to be a super star drag racing transmission, but instead it was really conceived and executed to be superior on the road course. Those gears with the straighter cut tended to generate less heat and during aggressive driving they distributed the load better lowering the chances of damage to the gear works inside the transmission. Because these were intended for road racing and heat was a primary enemy, the cases of M22s were all aluminum. Had they been cast iron, like the A-833, M22s would be far better known for their drag strip prowess. They’e certainly not a weak sister, but they have an Achilles heel or two that can show themselves at the exact wrong time. Watch Two Lane Blacktop to hear the music of an M22 if you’ve never heard it in person.
2.) The Borg-Warner T56 – The stick box that brought six gears to the American masses deserves a place on this list, even though lots of them have been killed by overzealous owners and drag strip violence since their introduction in 1992. The T56 was first designed by Borg-Warner for Chrysler as the transmission for the then new Dodge Viper. It was quickly adopted by GM for use in Camaros and later in Corvettes. The T56 also found itself installed into Mustangs, Aston Martins, and Holdens. With respect to “stock” T56 transmissions, the two most beefy factory units built were those designed to be punished by V10 Chrysler engines and GM LS mills. Both the Viper spec and SRT/10 truck spec T56 transmissions used a 30-spline output shaft and could handle 550 lb/ft of torque right out of the box. The Chevy SSR truck with a stick option actually got a stronger 32 spline output shaft! In contrast, early Camaro and Corvette examples were rated below 400 lb/ft of torque. Their rating crept up over the years, but never matched the Dodge versions strength. The modern Tremec 6060 was born from the T56 and continues to serve the performance car marketplace today with ratings of 600 lb/ft and up in some applications. It was a bit of a revelation for the domestic performance car crowd when the T56 hit the streets and the benefits of a short first gear were combined with a deep overdrive for great performance and economy. How many stories did we all read of magazine editors freaking out over the economy they got when lugging an LT1 equipped 4th-gen Camaro down the highway doing 65mph at like 1500RPM. Lots!
1.) The TH400 – A legendary driveline component was introduced in 1964 with the introduction of GM’s “Turbo 400″ transmission. The three speed automatic was designed to be a heavy duty piece and was the largest RWD automatic transmission in the GM family for an extended period of time. In stock form the Turbo 400 can handle about 500 lb/ft of torque. The aftermarket is awash with components to make them vastly more capable than that. The secret to the TH400′s strength is the cast iron center support inside the transmission that solidly anchors the transmission’s core moving components and its strength and robust nature keeps the TH400 from suffering some of the more violent deaths that other automatics can suffer. Other stuff like the large multi plate second gear clutches, and over running clutches for both first and second gear all contribute to the legendary toughness of this three speed. Outside of GM, the Turbo 400 has been factory installed in Ferrari, Jaguar, Rolls Royce, Bentley, and Jeep models. In the racing scene, Turbo 400s are all over the drag strips of America, can be found in lots of mud boggers, rock buggies, and virtually any other type of competition vehicle you can dream up. Up until 1991 when the 4L80-E was introduced, it the Turbo 400 was largely unchanged from its early 1960s roots. Turbo 400 = brute strength in gearhead speak.