Evolution of the T56 - Transmission Digest

Evolution of the T56

BorgWarner designed the T-5 5-speed transmission that became one of the largest by volume of production. Using a very simple single-rail shift mechanism, the T5 was lightweight, came with a 5th-gear overdrive to add to fuel economy, and had a torque rating useable in engines of the period. The first T5 models used brass synchronizer rings and straight roller bearings to support the countershaft. BorgWarner refined the design and created “The World Class T5,” which used synchro rings lined with the same kind of paper material used in automatic transmissions, and went to tapered roller bearings for the gear train. The weak point of the T5 was its small size, which was easy to package in the diverse models of cars that used it, but with such a small centerline between the input and the countershaft, torque was limited to a high of 330 lb.-ft.
Evolution of the T56

Up To Standards

Author: Mike Weinberg, Contributing Editor
Subject Matter: Technological change

Up To Standards

  • Author: Mike Weinberg, Contributing Editor
  • Subject Matter: Technological change

BorgWarner designed the T-5 5-speed transmission that became one of the largest by volume of production. Using a very simple single-rail shift mechanism, the T5 was lightweight, came with a 5th-gear overdrive to add to fuel economy, and had a torque rating useable in engines of the period. The first T5 models used brass synchronizer rings and straight roller bearings to support the countershaft. BorgWarner refined the design and created “The World Class T5,” which used synchro rings lined with the same kind of paper material used in automatic transmissions, and went to tapered roller bearings for the gear train. The weak point of the T5 was its small size, which was easy to package in the diverse models of cars that used it, but with such a small centerline between the input and the countershaft, torque was limited to a high of 330 lb.-ft.

At this point the carmakers were starting to have horsepower wars and the need for a higher torque 6-speed transmission led BorgWarner to create the T56 6-speed transmission. This unit looked like a T5 on steroids, continuing with a simple single-rail shift method and have both 5th and 6th overdriven provided excellent mileage at cruise speeds. It was rated at 450 lb.-ft. of torque and made its debut in 1992 in the Dodge Viper, with a 2.66-1 1st gear ratio. This unit was equipped with a 2-piece counter shaft. Gears 1-4 were mounted on the main shaft and 5th, 6th and reverse were mounted on an auxiliary counter shaft that splined into the front counter shaft.

In 1993 the GM F body (Camaro/Firebird) used the T56 and was offered in a 2.66 1st gear, a 2.97-1 1st gear, and in 1993-94 a 3.36 1st gear was available. The T56 continued to use the paper-lined synchro rings and employed a double cone 1st and 2nd gear synchronizer, while 3rd, 4th, 5th, and 6th remained single cone design. The double cone has the synchro ring with friction material on the inside and outside with an inner and outer steel cone. This effectively doubled the friction capacity of the synchronizer for smooth shifts without increasing the diameter of the rings.

In the late ’90s BorgWarner sold the transmission division to Tremec, a major tier-one supplier of manual transmissions. The stick transmission business was not growing and the market was concentrated on the sports and muscle-car segment, so BorgWarner concentrated its efforts on its transfer-case division that was on a significant rise due to the climbing sales of light trucks, SUVs and crossover vehicles. Transfer cases are used behind both manual and automatic transmissions. In 1998 Tremec began to update the T56 design, changing the synchro ring to carbon-fiber linings for smoother shifts and better durability. They also elongated the synchronizer engagement teeth for the 2nd- and 3rd- speed gears.

In 2001 the Viper models received a single piece solid counter gear replacing the previous 2-piece assembly. Ford now adopted the T56 in 2001 for the Mustangs with a 2.66 1st gear and an 0.80 5th gear and a 0.63 6th gear, both overdriven. The Viper and F body models retained the 0.74 5th and 0.50 6th gears. GM now began to use the T56 in Corvette models from 1997 replacing the ZF S6-40 6-speed that had been used since 1989. The Corvette models offered a 2.66 1st gear and the 0.74 5th and 0.50 6th as found on the F Body models, but Tremec now introduced triple-cone technology into the 1-2 synchronizer, and double cone for the 3rd, 4th, 5th, and 6th gears.

In 1999 the rings were changed from paper lined to carbon fiber. In 2001 GM changed ratios for the Z06 models using a 2.97-1st gear with a 0.80 5th and a 0.56 6th. In 2005 the Corvette base unit had a 2.66 1st with 0.74 and 0.50 overdrives, and a Z51 model was introduced with a 2.97 1st gear, and a 0.71-5th and 0.50 “touring” overdrive set. Starting in 2006 Corvette models got the one-piece solid counter gear in both 2.66 1st and 2.97 1st gear ratios.

One of the early upgrades we did to the T56 was substituting the 30-spline Viper main shaft for the stock 27-spline shaft in the F body cars. This was called “Viper Spec” and gave the unit a stronger output shaft that could take more shock loads from high rpm launches. It did not however increase the torque rating over the factory 450 lb.-ft. due to the fact that the gear train was the same stock alloy.

In 2004 Rockland Standard Gear engineered our Tranzilla brand custom-built T56 transmissions in response to demands for higher torque capacity from the race and enthusiast community. Our Tranzilla T56 unit used a 9310 alloy gear set and mainshaft, triple-cone and-double cone synchros with carbon-fiber rings, a steel 3-4 shift fork, and a custom gear set available in both synchronized and dog-ring models. The Tranzilla T56 could handle 1,000 lb.-ft. of torque, and the “Son of Tranzilla” was rated at 750 lb.-ft. of torque. Ratios available were a 2.97-1 1st gear set, a 2.66-1 1st gear set, and a close ratio gear set with a 2.29-1 1st gear ratio for road race applications. These units were the best of any model T56 at the time. One of the central design limits for the T56 was the use of stamped steel synchro keys (struts) and elliptical springs in the synchro assembly.

Drivers who rushed a shift or had a poor clutch release would frequently break the keys that were only stamped metal design. To cure this we began to use solid steel keys that were machined from billet alloy and were expensive. Now we found that while the keys were unbreakable, poor clutch release and bad habits would cause the synchronizer hub to crack at the key slot. Other companies began to market a solid key that was cheaper and made from powered-metal material. These powdered-metal products failed in a different way, where the ridge on top of the key to locate the neutral detent on the sliding sleeve would wear prematurely causing sloppy shifts.

While the billet solid keys were a definite improvement, but still needed better design for really smooth high RPM shifts. In 2008 Tremec came to the rescue with a new design of the T56 named the TR6060 for the OEM models, and named The Magnum for aftermarket sales. They completely redesigned the gear train and synchronizers to boost the torque rating and create effortless, smooth high RPM shifting. In order to increase torque capacity of the gear train, the gears were made wider and the synchronizer assemblies were made narrower so that all the components would fit inside a case that had the same internal dimensions as the T56 original design.

TR6060 major upgrades are as follows:

  • All models now used the one-piece counter gear.
  • Widened gear train with slimmer synchronizers.
  • Synchro ring diameter was increased with triple cone 1-2, double cone 3, 4, 5, 6, with all blocker rings the same size 1st through 4th.
  • Elimination of stamped keys and elliptical springs in the synchronizer assemblies. Tremec designed a high-strength plastic strut that encapsulated a ball and spring to set the neutral detent in the assembly, which eliminated broken keys and made for world class shift feel.
  • The fork pads were enlarged to handle the difference in the sliding sleeve design.

Note that many companies have offered “bronze shift pads” as an improvement over the OEM design. Our experience proves the bronze pads to have a very high wear rate due to the micro finish on the slider being incompatible with the bronze pad. The mismatch in surface finish is shown in an accompanying photo here of bronze pad wear after one 21/2-hour race. Pad failure is almost always due to low oil levels, a clutch that does not release fully, or a driver that rushes his shifts. The OEM product has lived through many 24-hour races at Daytona and LeMans in a properly set up transmission full of lube, and a fully releasing clutch. Bad drivers never finish a 24-hour race.

Tremec eliminated all of the previous faults in the original T56 design with the TR6060 and created a 6-speed with much higher torque ratings and world class effortless shifting. Taking advantage of this great design Rockland Standard Gear now began to manufacture the Magnum Tranzilla. Tremec stopped all production on T56 complete transmission assemblies. Service parts are still available for the T56 but the drop in production volume has caused a large increase in parts cost. We now can take a customer’s original T56 and convert it into a TR6060 Magnum internally. Many of our competitors will say this cannot be done using the original T56 cases. Truth be told, they just don’t know how to do it. We do it every day with parts we designed and engineered to take advantage of the design evolution. Why not convert a T56 to the advantages of the Tremec Magnum without the expense of buying a new unit? Our Tranzilla models are now all based on the Tremec TR6060 design with our own bulletproof internals that are match fitted to tolerances that the OEM cannot hold on an assembly line.

We have developed many products for improving Tremec’s designs. Tremec has a TKO 500 and TKO 600 5 speed unit, which is a direct bolt-in replacement for T5 transmissions, and Muncie and T10 4 speeds. These units will handle 500-600 lb.-ft. of torque and are based on the Ford “toploader” design that Tremec manufactured for Ford since the ’60s. These units are equipped with brass synchro rings that are not capable of making sustained high-speed shifts.

We designed and manufacture carbon fiber synchro rings for these units, which shift smoothly at 8,000 rpm. We manufacture a “Ford Race Box” for S197 Mustangs that gets rid of the sloppy remote shifter, and will also replace the unsuccessful MT82 Getrag 6 speeds in the newer mustangs. We make a kit for 2010 and newer F bodies that permits the use of an SFI rated steel bell housing required by many sanctioning bodies. There is a kit to convert an LT1 engine T56 to an, LS1 T56 removing the pull type clutch. We also created 2WD and 4WD Magnum Tranzillas for use in pickups for those owners who want improved fuel economy and the joy of shifting it yourself. There is a Magnum Tranzilla for Camaros, Firebirds, Corvettes, Cadillac CTS-V, GTOs, Mustangs, Vipers, Dodge Challengers, hot rods, resto rods, classic cars, and all forms of custom vehicles and performance cars.

Mike Weinberg is president of Rockland Standard Gear.

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