A Tougher T56

Here's the stock Viper Fifth and Sixth gears (left) compared to the upgraded individual Fifth and Sixth gears. Notice the internal splines are missing from the front of the stock gearset.

"Endplay tolerances are critical to the life span of these transmissions," says Kreppein. "Keep all clearances on the tight side, and you'll solve most of the performance issues of the T56." Auxiliary shaft endplay is being measured here.

The individual Fifth gear is pressed onto the auxiliary shaft. These new gears are the key to highway driveability for many applications that don't need to or can't lug along at 1,500 rpm at 75 mph.

Showing further differences, the extension housing for the LS1 (left), illustrates the need for different shifters and locations of the hole in the floorboard for different applications. Our transmission will be using the Viper rear housing.

The LS1's (left) front adapter plate centersection is quite a bit higher in the center, although otherwise identical.

Updated Viper gears (left) have much larger syncro teeth. Bust these teeth and the transmission won't stay in gear.

The transmission is assembled from front to back, so this is where it all begins, with the front adapter plate for an LS1 application.

At left, the LS1 mainshaft has 27 splines and is 1.175 inches in diameter. The stock Viper mainshaft is in the center, and the custom 30-spline, 1.290-inch unit is on the right. The custom shaft is the same thickness as the Viper, but it has splines farther up the shaft, allowing individual Fifth and Sixth gears, and therefore the ratio changes.

The stock aluminum shifter (left) is prone to cracking and failing--the cast-iron unit (right) is Tremec's answer to the problem. All rebuilt T56 trannies need one.