We devote a fair amount of coverage to transmission swaps, often for the sake of gaining an overdrive. When these swaps concern manual transmissions, it seems that most guys go for the sex appeal of a six-speed gearbox, sometimes with multiple overdrives and often providing additional strength. However, there is still something to be said for the often overlooked five-speed. Most five-speed boxes provide overdrive while maintaining underdrive ratios similar to the four-speeds of musclecar lore. Don't let the bad experiences your buddy had while power-shifting his stock '86 IROC deter you-today's five-speeds are much more durable than the original manual overdrive boxes. We've gathered the most popular offerings and listed their features and specs along with where to find them for your perusal. Just a little more food for thought as you ponder future upgrades.
Borg-Warner/TTC T5The Borg-Warner T5 manual five-speed transmission has been used in a wide variety of applications since it was first put into production in the late '70s; in fact, there are currently over 260 part numbers for T5 assemblies on the books. This has resulted in numerous variations over its production 20-plus-year lifespan. The original intent of this gearbox was to provide a relatively lightweight (under 80 pounds), smooth-shifting manual transmission with overdrive for improved fuel efficiency. But it wasn't long before it was providing an excellent bridge between performance and economy. The two versions most familiar to car crafters are the '83-'95 Ford Mustang 5.0L and the '83-'92 V-8-powered Camaro and Firebird. Despite the similar parameters of both of these vehicles, the gearboxes used in each are significantly different from one another, and to make matters even more confusing, there were changes to each during their respective runs. The upside is that these changes were almost always done in the name of increased durability, as the Detroit horsepower race escalated.
The primary differences in T5s for both the Mustang and the F-car can be split into two classifications: World Class (WC) and non-World Class (NWC). The term World Class is often thought to be reserved for the best T5s built, but actually there were further upgrades after this nomenclature was first applied. The World Class upgrades consisted primarily of caged needle bearings for First, Second, and Third gears, compared to the gears riding on a solid shaft as they do in NWC versions. The counter gears in WC boxes use tapered roller bearings in place of the standard rollers in the NWC. World Class boxes also use fiber-lined blocker rings on First through Fourth gears to improve synchronizing for smoother shifts. Despite these upgrades, the first WC boxes carry the same 265-lb-ft torque rating as the NWC units before them, probably since the changes were actually aimed at improving the transmission's operating performance rather than its integrity.
The NWC gearboxes use a 2.95 First gear while the later WC units have a 3.35 First. This holds true for both Camaro and Mustang boxes, though the Mustang went to the WC for the '85 model year while the Camaro didn't make the switch until '88. For the '90 model year, Ford worked with Borg-Warner to further upgrade the T5, resulting in new Second and Third gearsets using course-pitch gear teeth and higher nickel-content steel. These changes raised the torque rating to 300 lb-ft in Mustangs. Later, the T5 was further upgraded to harness the power of the '93 Mustang Cobra. This version, dubbed the T5 "Z" because of its Ford part number designation, has tapered output bearings and a steel front-bearing retainer (versus aluminum) among other things, pushing its torque rating to 330 lb-ft.