2007 Tremec T56 (MM6/MZ6/M12)

2007 Model Year Summary
Tremec T56 six-speed manual car transmission

• There are no changes for the 2007 Model Year


The 6-speed uses Texaco ATF Type III 1863 fluid and is certified "fill-for-life," requiring no fluid changes. The clutch is activated hydraulically, which automatically compensates for clutch disc wear, eliminating manual adjustments. The Tremec T56 six-speed was originally designed to require virtually no maintenance.


Originally, the Tremec T56 evolved as a higher-torque capacity, six-speed version of the proven M49 five-speed manual transmission, and was introduced in the 1993 Chevrolet Camaro and Pontiac Firebird. It was also added to the 1997 fifth-generation Corvette.

Further applications included high-performance models, such as in mid-2004 the Cadillac CTS-V, which uses the LS6 engine mated to the M12 version of the six-speed.

The sixth-generation Corvette with Z51 option uses the MZ6 version of the six-speed, with ratios from the M12, which are higher ratios in first, second, and third gears than the MM6, which is the standard gearbox, as well as a lower-ratio fifth gear to increase top speed in fifth gear with the LS2 engine.

When the high-performance Z06 version of the Corvette was introduced for 2006, a stronger single-piece countershaft replaced the previous two-piece countershaft for the MM6. The output shaft was enlarged to a 32-spline unit, which is more durable than the 27-spline unit used in the standard Corvette applications. Also in 2006 the 6L80 six-speed automatic transmission was introduced, and the bolt pattern for the rear of the case extension of the MM6 was changed to match the same bolt pattern as the automatic’s.

Bearings in place of bushings lower the friction of the shift rail movements for the Corvette, making the shifter feel lighter and more direct. Corvette and CTS-V applications also use carbon for the reverse gear synchronizers, which improves durability. To enable even quicker shift throws for both standard Corvette and Z51 option, side-to-side and fore-aft shift rail detents have been moved closer to their stops.

The synchronizer sleeves have been lengthened for applications in the CTS-V, which effectively shortens the distance the synchronizers travel when engaging a gear. This reduces the shift throw distance at the shifter, for quicker gear changes.

Design features include a combination of double-cone and triple-cone synchronizers on all forward gears. Synchronizers act like clutches to speed up or slow down a gear that is being shifted to. Double-cone synchronizers have two friction surfaces to effect this gear acceleration, and triple-cone synchronizers have three friction surfaces. The greater the friction surface, the easier the transmission is to shift. In addition, double-cone and triple-cone synchronizers are smaller in diameter than a single-cone synchronizer with the same friction area allowing the transmission to remain more compact.

Refinements common to the design of all six-speed Tremec T56 products include needle bearings on all forward gearsets and 5th and 6th gear synchronizers located on a countershaft. The countershaft location of the 5th and 6th gear synchronizers allow those gears to be selected without affecting the 1st through 4th gearsets, contributing to ease of shifting.

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