As confused as Blue Oval and Mopar fanatics may be in their misguided hot rodding proclivities, at least they know a good automatic transmission when they see one. How else can you explain the overwhelming number of Outlaw 10.5 Mustangs running Powerglides and mega-buck Pro Touring Mopars equipped with 4L60 overdrives? While GM has continually set the gold standard for swap-worthy powerplants-whether they're Rat motors, 350 Chevys, or LS small-blocks-the engineers in the transmission department have never played second-fiddle to the guys in the engine shop. As a testament to the inherent brilliance of their original designs, the Powerglide and TH400 have been staples of on-track competitors for 60 and 50 years, respectively. Likewise, the 700-R4/4L60E has already been in production for nearly 30 years, and it gets better with each of GM's successive iterations.
Advances in modern friction discs, clutch plates, and lightweight shafts and internals have enabled building transmissions that are more durable and efficient than ever. Furthermore, the recent introduction of GM and aftermarket six-speed automatics means that there are more options available than ever for enthusiasts. With the grueling pace of transmission development, we felt it prudent to sit down with some industry experts to get the latest scoop on current R&D trends. Our cast of pros includes Regis Finn of B&M, Zack Farah of Gearstar, Achilles Thomas of Monster Transmission, and Stanley Poff of TCI.
Clutch Packs
Zack Farah: "High-quality frictions and steels play a large role in the performance of a heavy-duty transmission. Stock applications use paper friction materials and plain steels intended for smooth shifts in daily-driver applications, such as grandpa's '87 Caprice. The most popular brands of performance friction materials are Raybestos' Racing Red and Alto's Red Eagle frictions. For high-performance applications, they afford a greater coefficient of friction between the steel plates and clutch plates. When paired up with Kolene-treated steels, this clutch pack configuration creates the greatest torque capacity per square inch of clutch surface area. In performance street/strip applications with moderate horsepower, we employ the Raybestos Red frictions with Kolene steels manufactured to standard thicknesses. In full-race applications, we use Raybestos/Kolene expanded capacity clutch packs. These are manufactured to a thinner dimension, both the steels and friction plates, so we can fit extra clutches and steels to increase total clutch surface apply area."
Stanley Poff: "The stock friction clutches that come from the factory were designed to have some slippage in them in order to allow the transmission to shift smoothly. The specially designed Red Eagle clutches used by TCI withstand higher temperatures than any other clutch available, in our opinion. We have even worked hand in hand with Alto to develop friction clutches and steel clutches for newer-model transmissions, as well as older transmissions, that are exclusive to TCI. The friction paper in these clutches is saturated in a phenolic resin and then cured. Red Eagle clutches are designed with a softer, more resilient base paper. They're not only saturated in a phenolic resin, but also have a second saturation in silicate. The silicate imparts high heat resistance to the friction paper."