For once, maybe we should cut the Blue Oval loyalist some slack. Sure, many of them would rather swallow their pride and bolt a venerable GM automatic behind their motors instead of taking their chances with a junk C6 or AOD, but who can blame them for exercising common sense? Even ego-stroking marques such as Ferrari, Bentley, Rolls Royce, and Jaguar have all relied on GM transmissions to reliably shuttle along their pretentiously ignorant clientele at some point in time.
The truth of the matter is that there are so many bulletproof GM trannies, it can be tough to choose the best unit for your application. Good problem to have, isn't it? Within the GM's camp of torque-transferring studs, there are proven dragstrip heroes such as the Powerglide, TH350, and TH400. Then there are cheap-and-easy early overdrives like the 700-R4 and 200-4R. Likewise, evolution is constant. The plethora of recently updated electronic overdrive units includes the 4L60, 4L65, 4L70, 4L80, and 4L85.
Naturally, this diverse lineup of all-stars requires doing your homework before investing in a performance transmission. Zack Farah of Gearstar is here to help with your studies. He's been in the transmission business for nearly 30 years, and his hoards of happy customers are a testament to his innovative and exhaustive approach to rebuilding and testing GM automatics. In addition to helping you through the selection, we had Zack differentiate between various GM trannies, explain the basics of how they work, give tips on how to swap in an overdrive, walk you through the rebuild, and lend some tips on promoting parts longevity.
History
Gearstar owner Zack Farah got his start in the transmission industry 28 years ago at Tri Star International, a company that built over 100 transmissions and 300 torque converters every day. While the bulk of production at Tri Star was as an OEM supplier, high performance transmissions were Farah's true calling. "The high performance or racing transmission customer is building his pride and joy, and the demands placed on these machines are very different from those placed on passenger vehicles," he explains. Realizing that no company was offering anything other than off-the-shelf transmissions, Farah split from Tri Star and started Gearstar with the goal of manufacturing the finest performance automatic transmissions and converters available. "Each one of our transmissions is custom-manufactured to a car's specifications and application, taking into account horsepower and torque output, cam specs, rearend gear ratio, rear tire diameter, speedo type, vehicle weight, and vehicle use. Gearstar utilizes the most experienced technicians in the industry."
Don't Try This At Home
Due to the complex nature of automatic transmissions, few DIYers will ever attempt to tackle a rebuild. According to Farah, that's not necessarily a bad thing. "A high performance transmission like the ones Gearstar manufactures simply cannot be built by DIYers". The master builders at Gearstar each have an average of 25-30 years of experience. "Our builders have the latest diagnostic and testing equipment, which enables us to calibrate shift points, set redline, tune shift quality, check pressures and temperatures, and track down vibrations, noises, and leaks. Additionally, if one of our builders has a question, he can draw on the experience of other seasoned technicians. What Gearstar offers is unequalled in the industry, let alone something built in someone's backyard."