Torque Ready With TREMEC Magnum-F Transmission
Chevy Hardcore / June 26, 2023 / Rob Krider
Drag racers love automatic transmissions. However, road-racers, autocrossers, and time-trial folks prefer to row their own gears with a manual. The drivers who do more than go straight want to put the car in the gear they need for the next corner and stay in that gear until they say otherwise. Automatics tend to change gears “when they feel like it.” No artificial intelligence is needed with a manual transmission, just a simple gear shift lever and some synchros. Now, full disclosure, with the choice to row through the gears at your heart’s desire on the road course comes the opportunity to cause damage to a transmission, especially a bone-stock transmission that wasn’t designed to handle the beating a long track day can throw at a car with lots of torque. This is where TREMEC can help.
Help, My Old T-56 Has Had It
The T-56 has been a tried and true manual transmission. Originally designed for the Dodge Viper, T-56s also found their way into Corvettes, fourth-gen Camaro/Firebirds, and 2003-2004 Ford Mustang Cobras. Who knew a single manual transmission was used by Dodge, Chevy, and Ford? As solid as the transmission was for stock applications installed on some high-performance machines, over the years as horsepower and torque numbers increased the T-56 started to show a few weak points. Turning the inside of a manual transmission into metallic spaghetti is no way to enjoy your day at the track. To solve these issues, TREMEC took the T-56 and upgraded the design to create the TREMEC TR-6060 which the Magnum-F is based on.
The Tech of TREMEC
The TREMEC Magnum-F transmission was built specifically to bolt into GM F-body cars (hence the -F suffix) and can withstand 700 lb-ft of torque (or 949 Newton-meters if you are into the whole metric thing). According to Mike Kidd, Aftermarket Business Unit Manager at TREMEC, “The Magnum-F is made from 100-percent brand-new OEM-quality components, this isn’t a rebuild. What really makes the Magnum-F a bulletproof transmission is the size of some of the internal components. First, the transmission has larger diameter, but narrower, synchronizers, which allows for added face width on speed gears. The larger the face-width on the speed gears allows for more mesh and more strength.” This is one of the reasons you can send 700 lb-ft of torque through the Magnum.
Over the T-56, the Magnum-F boasts increased face-width on all gears, a robust combination of double- and triple-cone synchronizers, enhanced webbing in the main case, and provisions for a transmission fluid cooler circuit. The shifter provides a precise and communicative shift feel that all Magnums are known for. The unit is relatively light, tipping the scales at just 140 pounds before transmission fluid is added. Even though it’s a manual, TREMEC recommends Dexron III Automatic Transmission Fluid be used internally.
The upgrade from a T-56 to a Magnum-F is a relatively simple swap but there are a few details that have to be dealt with. Namely, the yoke for the driveshaft has a different spline count. The Magnum-F requires the use of a 31-spline slip yoke and modifications to the driveshaft length. When doing this swap on a fourth-gen F-body this is one detail that can’t be ignored.
If you have ever done transmission work then you know it certainly isn’t the most enjoyable weekend project. You will be under the car, stuff is going to drop into your eyes, and your knuckles will be bloody, but in the end, the old transmission will eventually come out.
Besides having to shorten the driveshaft and change the yoke, installing the Magnum-F also requires changing the flywheel, clutch, and hydraulic slave cylinder (which are things you would normally replace anyway during a transmission swap). We sourced a lightweight clutch and flywheel from SPEC to mate with our Magnum-F.
The Magnum-F is rated at a maximum engine speed of 7,800 rpm, which is beyond what we will be turning our engine at. When you purchase the transmission you get your choice of two different gear ratio sets with a double overdrive. Transmissions with a double overdrive have two gears, 5th and 6th in the Magnum-F, that spin faster than 1:1.
With the different iterations of the TREMEC Magnum transmissions, there are different shifter locations. Where the original Magnum shifter location may prove too far forward in some cases, and the extended length Magnum XL’s too far back, the Magnum-F’s in-between position often proves to be just right for many LS-swapped vehicles. However, the Magnum-F was designed to bolt into a fourth-gen F-Body with zero modifications to the floorpan.
Because this upgraded transmission was designed and marketed to replace a T-56 in a fourth-gen F-Body, our swap was relatively drama free. The transmission bolted up as advertised and fit in the chassis as if the car came from the factory with it. While we were at it we chose to upgrade the strength of our driveshaft to match the new transmission. Nobody needs a weak link in the drivetrain.
Before we can hit the track, TREMEC does have a break-in procedure for the Magnum-F that involves putting 500 miles on it. TREMEC recommends that these break-in miles be at various speeds and engine RPM. We plan on getting through the break-in miles quickly so we can get to autocross events and begin getting laps in. Come back soon to LSX Mag to see our next update on Project Dirty Bird.