Call us self-centered bigots, but we didn't do it for the polar bears. Granted, we live in an era when burning fossil fuels is as evil as capitalism, but our motives are a bit more self-centered. If our '75 Laguna S-3-aptly dubbed Project Talladega-is to live up to its family hauler mission statement, an ancient three-speed slushbox just won't cut it. Relaxed freeway cruising calls for an overdrive transmission, but with a 525hp 408 small-block in the works for our 4,200-pound behemoth, long-term street durability seemed elusive at best. To help solve our dilemma, we turned to Greg Ducato of Phoenix Transmissions (www.phoenixtrans.com), who set us up with one of his company's top-of-the-line 700-R4s.
In the walk of GM overdrives, those who don't care to fiddle around with costly and complicated computers have two options: the 700-R4 or the 200-4R. Although we were initially leaning toward the leaner 200-4R, Greg quickly altered our errant path. "In my opinion, the 200-4R is best suited to lightweight vehicles producing 400 hp or less," he says. "It's true that Turbo Buick racers have thoroughly abused these transmissions with great success, but after the 400hp mark, they require so many mods that they become very expensive and hard to live with on the street. I don't think there's a single component in a 200-4R in stock trim that's as strong as the 700-R4. The 700-R4 also has a deeper 3.06:1 First gear compared to the 200-4R's 2.74:1 ratio."
Among the multitude of modifications Phoenix performs to turn a standard 700-R4 into one of its PT700R4SX is the installation of a heavy-duty reaction sun shell, a five-pinion rear planetary set, billet Second- and Fourth-gear servos, high-capacity sprags, and high-energy frictions and bands. All this adds up to a 700-R4 that can handle up to 600 hp, and provide thousands of miles of reliable street cruising. While we're all for saving a buck and turning our own wrenches, rebuilding an automatic trans is a tedious affair that's probably best left to an expert. Here's what it takes to build a bulletproof 700-R4.
Case Prep
Phoenix's case preparation procedure is a separate story in itself, and the results are simply stunning. Since the cores used for its 700-R4 builds are anywhere from 15 to 20 years old, each case is first hand cleaned with a brush and solvent. Next comes bead blasting, followed by steam cleaning. Afterward, the case is flat-filed by hand on all mating surfaces to eliminate casting flash before all the boltholes are tapped. The most interesting part of the procedure is the finishing process, in which the case is immersed in a vibratory refinishing machine. Essentially a giant tub filled with 4,000 pounds of ceramic alloy media, a special detergent, and a brightening solution, the machine leaves a brilliant semi-polished finish on the case after the 1.5-hour process is complete. Additionally, the refinishing procedure closes case porosity for improved strength. After another round of steam cleaning, the case is finally ready to anchor the guts of a bulletproof transmission. -Stephen Kim
