Tremec T56 Transmission - Gearing Up For Battle

The vast majority of g-Machine enthusiasts are of the clutch-pedal-and-H-gate variety, and the most popular trans of choice is undoubtedly the Tremec T56. And why not? It's all over the salvage yards and eBay, it's extremely affordable, remarkably robust, and offers double-overdrive cogs for respectable gas mileage even with a deep ring-and-pinion set. Nevertheless, nothing's perfect, and the Camaros, Mustangs, and Vipers most T56 transmissions started life in have a propensity for being run hard. Enough weight, power, and clutch bite-as in 6,000 rpm launches on Mickey Thompsons-will do in even the mighty T56 and quickly reveal its weak links. We teamed up with T56 Rebuilds and Rockland Standard Gear to show you how to diagnose the health of your T56 and beef it up to suit your application if necessary.

Anatomy of the T56
By far, the most common source of T56 transmissions on the used market is the Fourth-Gen F-body, primarily due to its longish production run from '93-'02. Although the T56 has been used in the Dodge Viper since the early '90s (in addition to the '03-'04 Mustang Cobra, '04-and-up Pontiac GTO, and Cadillac CTS-V), much lower production numbers make them less likely swap candidates. Likewise, the C5 Corvette-with its rear transaxle layout-makes a potential conversion far less appealing. Nonetheless, other than varying rear tailshaft housings, front adapter plates, and bellhousings, the transmission cases and the internal components within them are remarkably similar in each version of the T56. Consequently, the rebuild procedures outlined in this story are universal, and parts from stronger variants of the T56 easily interchange with its more feeble brethren. All T56s feature die-cast aluminum construction, paring mass to a trim 130 pounds.

Breakage
The most common F-body box features an official torque capacity rating of 450 lb-ft, but hoards of racers have subjected them to well over that figure without much fuss. From a durability standpoint, the primary difference between the Viper trans and lesser T56s is its thicker output shaft measuring 1.290 inches versus 1.175 inches. Likewise, the Viper shaft allocates its torque load over 30 splines, as opposed to 27. As far as parts failure from sheer driveline shock is concerned, the output shaft is the first to go.

Although upgrading to a Viper output shaft is a must in hardcore drag racing applications exceeding 900 horsepower, very few street cars actually break the stock piece. In fact, non-Viper T56s can handle close to 750 hp in most street applications. On the other hand, most of the components replaced during a typical rebuild are normal wear and tear items, such as synchros and friction cones. Improperly setup clutches that don't fully disengage compound the problem. In other words, the T56 has a lot more strength than the average backyard clutch installer has common sense, and is therefore much more durable than its reputation may suggest. "Most of the problems people have with their transmission-like grinding or popping out of gear-are due to not addressing the hydraulic system when replacing a clutch," says Joe Overton of T56 Rebuilds.

Regardless of whose fault transmission wear may be, the T56 isn't perfect. Due to its small diameter in relation to the 1-2 shift fork, the factory cast aluminum 3-4 fork is a common problem area. Of course, the 5-6 fork is smaller still, but hard shifts into overdrive are rare. Rebuilds typically include an upgraded steel 3-4 fork along with rugged billet steel keyways to replace the factory aluminum pieces. Furthermore, upgraded carbon fiber synchros further improve resilience to gear banging. Synchronizer sleeves and fork pads simply wear out as opposed to breaking, so replacement with fresh stock parts will suffice. All parts are available directly through Tremec, and its distributors, such as Rockland Standard Gear.

Repair
We're all for turning your own wrenches and saving a few bucks, but rebuilding a transmission is probably best left to the professionals. Not only is there a harrowing volume of gears, bearings, pins, shafts, screws, and locks in varying sizes that all look the same, but misplacing just one of them can blow up your trans. In comparison, assembling a short-block is a walk in the park. If you're still feeling rather intrepid, a quick look through a service manual will probably change that pretty quickly. Seeking the expertise of someone much smarter than ourselves, we closely observed Joe Overton of T56 Rebuilds as he performed a basic rebuild. Here are the highlights.

The final step before removing the trans case is removing these two bolts. They hold the internal linkage selectors, which also guide the shift rail. The factory uses red Loctite to hold them into place, so it's necessary to heat them with a torch to loosen them up before attacking them with a breaker bar.	With the transmission case removed, you can see how gears 1 through 4 and the 1-2 and 3-4 shift forks are oriented. The counter shaft is in the background.	Worn shift forks and pads, which cradle the synchronizer assembly, can cause the transmission to pop out of gear. On the bottom is the cast aluminum factory 3-4 shift fork and on the top is the new steel fork.
Just like a clutch, the synchronizer cones wear out over time. Cones should be replaced with every rebuild, and the aftermarket piece from Rockland Standard Gear (on the right) features noticeably beefier padding and a higher coefficient of friction.	The hollow aluminum key on the left is used throughout the trans. The billet replacement on the right does a much better job of holding parts into place and reducing the possibility of failure.	The teeth on the synchronizer sleeves (sliders) eventually get rounded and wear out. They are replaced with fresh factory units.
With the trans case bolted to the adapter plate once again, it is critical to set the endplay of the output shaft and counter shaft between .002 and .003 inch. Improper endplay will cause sloppy shifting and popping out of gear once the transmission reaches operating temperature.