Which 6 speed is the best for my project?

Clarifying the big differences between the original T-56, the TR-6060, and T-56 Magnum

The T-56 6-speed transmission has been highly sought after for transplanting in hot rods and muscle cars ever since Dodge released the Borg Warner variation in the 1992 Viper. Since that time the T-56 has undergone several design changes and multiple application variations up to the current Tremec built TR-6060 OE model and the Magnum aftermarket version. If you’re on the hunt for the best version to use in your project, you will find a lot of good and bad information floating around about the differences, and reasons why you should go one way or another. We want this article to serve as a good foundation to work from and hopefully equip you with a good understanding of the differences in the various models of “T-56” transmissions that are available.
First things first though, the term “T-56” should be considered a vague and generic label for all versions of this 6 speed manual transmission. Each variation of the T-56 was specific to a certain model of vehicle, with specific gear ratios and torque capabilities. This means that if you have a Viper T-56 or a Camaro T-56 you have two entirely different transmissions. Yes, some of the parts are interchangeable, but the two should not be considered the same. Also, with the new generation TR-6060 and Magnum transmissions there are a lot of similarities and just as many differences. This is important to keep in mind when sourcing parts and determining fitment compatibility because the different variations will not interchange with each other. The closest resemblance will be with the F-Body LS T-56(98-02) and the new T-56 Magnums. The 2002-2003 Mustang Cobra T-56 and the Ford T-56 Magnums are also very similar other than the Mustang version utilizes a 10 spline input rather than the 26 spline found on all newer Magnums. They will interchange in the same bellhousing, clutch, and T.O.B. application, but that’s where the similarities end.

The most popular “take out” version used was the 1998-2002 GM F-Body T-56. These were plentiful in the salvage yards and were easy to get rebuild parts for, but did lack in torque capacity and had a few other faults that were eventually overcome with the emergence of quality aftermarket parts. This wasn’t much of an issue until everyone figured out how easy an LS engine could make 500+Hp. The original F-Body T-56 was rated at 450 lb/ft of torque capacity, and with a few minor upgrades could handle an aggressive driver, but as with most things hot rod related we needed something more!
With the ever increasing demand for more power in the factory muscle car programs Tremec released the TR-6060 transmissions for the 2007 Ford Shelby GT500 and for GM in the Corvette, Cadillac, and new 5th Gen Camaro platforms. This new design took the increasingly popular T-56 platform to the next level with a huge increase in torque capacity. The internals and most of the externals were completely redesigned for this new model allowing it to survive and thrive behind the Ford Modular & GM LS series of engines and the incredible amount of power they were making. It was also at this time that Tremec recognized the need for a similar version geared directly to the custom aftermarket, and in 2009 released the Tremec 6-speed Magnum. With the increased universal adaptability of this new Magnum the aftermarket exploded with products to support installation behind all the popular engine platforms in nearly any vehicle. Along with its 700 lb./ft. of torque rating the Magnum was the answer the hot rod market was waiting for; to get a high quality manual transmission that not only handled the power, but did it without compromising shift quality or the desire for a deep overdrive. It also didn’t take long for upgrades to become available for the Magnum to take it into the next level as a world class leader in the racing arena.

In order to get a better grasp on what the most important differences are between the early T-56 and the later Magnum/ TR-6060 you have to open up the case and take a look at the internal components. The ability for the new Magnums to handle the increased torque capacity was largely dependent on increasing the width of the gears which meant a redesign and decrease in the width of the synchronizer assembly. Another key factor was a redesign in the way the gears were constructed. The original T-56 used a machined 1-piece forging that limited the design of the clutching teeth. The new Magnum design went with a 2-piece unit that was pressed together and then laser welded. This allowed for an optimization of the tooth angle and profile for both the clutching ring and gear. This all new design eliminates the possibility of an “overthrow” during a gear shift. The blocker rings were also changed to a 3pc design for 1st & 2nd and double cone design for the rest of the gears including reverse. This change increased the surface area of the blocker rings allowing for a quicker gear change under high RPM and torque loads. Speaking of shifting gears, a common complaint with the early T-56 was the shift fork design. The early T-56 had a 2-piece shift fork that would commonly bend or break when pushed hard, which then resulted in a steel fork upgrade. The new Magnum design converted this over to a 1-piece casting in addition to a better shift rail design. A few other key changes that allowed the new Magnum series to withstand an increase in torque capacity was a 26 spline input shaft with increased bearing size as well as a standard issue 1-piece counter shaft.

You can see the blocker and friction rings from the TREMEC TR-6060 and Magnum at left and the T-56 at right. Note that the number of friction surfaces is what designates the basket as a double or triple cone.

Aside from all the great updates that the Magnum was given on the inside we must take into consideration the exterior changes as well. The new Magnum was created to be a swap-friendly unit and was given 3 shifter locations, mechanical and electronic speedometer outputs, a stronger 31 spline output shaft, dual pattern crossmember mount, and no skip shift solenoid. There have been many hot rods built with the early F-Body T-56 that are now worn out and in need of a rebuild or replacement. The one problem we are starting to see is that some of the gears are becoming more difficult to find, and depending on the condition of the transmission in question, it may be more cost effective to buy a new Magnum rather than rebuild an older T-56. Here in lies the dilemma. The front of the transmissions are interchangeable, so the Magnum will bolt right into the same bellhousing that the early T-56 uses, but the rear of the transmissions use different tail housings. This results in the need for a change in driveshaft length, cross member location, and shifter placement. It is possible, with some custom machine work, to adapt the older T-56 tail housing onto the new Magnum main case to give you the upgraded internals while maintaining the fitment of the original T-56. This ends up being a little more of an expensive transmission, but the added cost in converting the transmission will likely be less than the cost of converting the vehicle to accept the Magnum in its standard configuration.


The bottom 3 green arrows denote the 3 possible shifter locations on the Magnum 6-speed. Another key feature was the elimination of the “skip shift” solenoid found on the factory units which is shown by the bottom red arrow.

Today it is also common to see many of the new TR-6060 transmissions showing up in salvage yards still bolted up to the factory engines to be sold as conversion packages. This swap can be done in older hot rods, but be warned that there are a few hurdles to overcome should you decide to go this route. Yes, the transmission is built on the same platform as the aftermarket Magnum, but keep in mind that if you buy one that was installed into a Cadillac or Camaro it was built specifically for that car in terms of power capacity and gear ratios so you will want to take that into consideration when planning out your
drivetrain. You will also notice that the factory TR-6060 uses a remote mounted shifter. This can be tricky to adapt into an older muscle car and is the only shifter available for that transmission. The TR-6060 also utilizes a flange style output rather than a traditional slip yoke for the driveshaft. This will require you to use a driveshaft that has the slip yoke built into it which is typically much more expensive than a traditional driveshaft and not easily replaced should it get damaged while on the road. You will also be limited to an electronic only speedometer output. One last item to consider is that with all the newer TR-6060 transmissions the bellhousing is integrated into the front cover of the transmission. This limits the engine choices available to use that transmission behind. Typically that isn’t a concern, but if you are considering it for any engine other than the GM LS series it will be an issue.


Although some of the higher-torque-application T-56s received a 1-piece cluster, or countershaft, 2-piece clusters (left) were standard for most applications, such as the Cobra and 4th Gen F-car. In the TR-6060 and Magnum, all cluster gears are of the 1-piece variety. You can also see the difference in gear face widths in this photo

We thought it noteworthy to also mention some of the more uncommon T-56 applications and how they relate to the more common units. The following versions of the T-56 were in a much lower supply overall so the options to use them in alternate applications were very limited. In many cases the Magnum is typically a much better alternative due to the available aftermarket support. The Viper T-56 has always been a unique, one car application, but with its original popularity for conversions, there are bellhousings, clutches, and pilot bearings to allow it to be used behind engines other than the Dodge V10, but they are very limited, and there aren’t as many options for supporting components. The other most common unit is the GM LT1 version of the T-56 used from 1993-1997. These were unique in the fact that they used a pull style clutch pressure plate rather than a traditional push style. There have been many of these that were converted to work like the later LS style by changing the front cover and input shaft so that it could be used with the push style clutch. The Corvette started using the T-56 in 1997, but since they are a trans-axle set up, they are not as easily adapted over to a standard RWD configuration. The Corvette T-56 can be converted to use with a standard RWD GM T-56 case, but may not be worth the effort unless you have readily available parts that can be had for little expense. The Mustang T-56 was one of the least used since it will only work on the Ford engines and the supply is very limited. There was also a time frame in the mid 2000’s when GM was using a hybrid of the older T-56 and new TR-6060 in applications such as the SSR pickup and Pontiac GTO. These are also unique and are best used in conjunction with the LS type of engine it was mated to from the factory.
It is not uncommon to find articles detailing how to convert these units to work as something different than what they were designed for, but be careful that you aren’t getting yourself involved in a project that will end up costing you more time and money than buying a brand new unit with a warranty. The converting of an older T-56 was definitely a viable solution 10 years ago, before the Magnum was released, but doesn’t make as much sense today unless you can get the parts for cheap or free. Even so, be careful of the “donated” parts you end up with, many times they are from different models or variations of T-56 and aren’t always compatible with each other and in the end all you really have is a bunch of parts that don’t fit and hours of aggravation invested in trying to make them work.
There are still other examples that can be covered in regards to the T-56, Magnum, and TR-6060, but this information should serve you well as a good overview and give you a solid direction to move in. As always, anytime you are building a hot rod for yourself, build it the way you want to do it. If it makes sense to buy new, then do that. If you love to tinker with used parts, then there are also plenty of resources to help you build your own T-56 from salvaged parts. Either way, have fun with the journey, and give us a call if we can help.

*Photo Credit: Tremec Corporation

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