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(Insert screeching organ music here) Rebuilding an automatic transmission… Easy guys. I know….even the thought of undertaking such a task is scary enough to contemplate. Fortunately, actually doing it is a job best left to the pros in the know… Grand High Wizards of this Blackest of Arts … "Tranny guys." In recent months, the rockcrawler crowd has discovered one of the "secrets" that the rest of the off-road world has known for years. Automatic trannies are superior to their manual counterparts in many respects. They're easier on drivetrain parts, make for easy swaps, and can handle ludicrous amounts of torque without breaking a sweat. Because of their torque converter, their actual reduction under load belies the "hard ratio" of the gear set. In short, there's a lot to like. Unfortunately Automatics have some serious downsides as well. The question becomes, like many things, a trade off. When compared to a manual transmission, what benefits are you after, and what are you willing to sacrifice to get them?
1st is first gear. 2nd is Second gear D is Third gear Period. There's no untimely shifts, no surprises and additional compression breaking on demand. Plus, a manual valve body results in less heat build-up and less wear on the transmission in comparison to it's full auto counterpart. For the full scoop on turning our "highly" worn C6 into a tire chirping psudeo-stick shift, we went straight to the professionals at Valley Transmission in ElCajon CA. Transmister Greg Bohem has been in the business for just about a 1/4 century and built automatics that have withstood the not-so-tender mercies of 1500HP supercharged big blocks and naturally aspirated small blocks alike. From the streets to the strips to the sands and rocks of Baja, Valley trannies have long been the choice of those in the know. We had a chance to spend some scarce time with Bohem at his shop in-between teaching assignments. Bohem you see, is in demand in the southern California in more ways than one. Beyond his skills on a wrench, the seasoned pro has a talent for taking his years of skill, theory and experience and distributing it among those with an auto-academic thirst for knowledge. The information Bohem imparted on us in a short time could easily fill a book. Unfortunately, most of it would be well over the heads of the average off-road enthusiast out for some pointers on their own transmissions - this writer included. "The greatest problem an automatic has is heat build up. But it's the source of that heat build up that people often miss - lugging the engine. Today's engines are built to rev higher. Naturally modern transmissions are built to function at these elevated levels. But even older trannies are often lugged down to the point where the converter is slipping and that's where the heat comes from."
"There are many ways to disperse that heat. Most often the addition of an add-on cooler will take care of the majority of tranny temp woes, but most people make the mistake of bypassing the stock cooler that's a part of the radiator. It's an easy mistake to make." "Lets say your vehicle always travled at 55 mph or so where air was constantly flowing through the cooler. It would work fine. But what happens when you hit stop and go traffic? The tranny never achieves fluid coupling, gets very hot, and there's no airflow through the aftermarket cooler to disperse the heat. That's when parts melt down and transmissions burn up." "Now with the factory set up, you have the radiator acting as a fluid to fluid cooler to disperse that heat - doing what it was designed to do. The best of all worlds is to plumb the aftermarket cooler through the factory system. In extreme cases, you can even add an additional fan. This way you get the benefits of both without sacrificing any efficiency at low speed." "We get a lot of questions like "How much power can my XXX transmission handle?" It's not a question of "how much power," but "What kind and where that power is made." "For example, the average engine delivers it's power smoothly over a wide RPM range. This allows fluid pressures to build accordingly within the transmission and results in proper functioning. But when you start talking diesel engines that make all their power down low, or drag race engines that make it all at 9000+RPM there are special considerations."
"Then there are lubrication considerations that vary from model to model. In general, more lube is a good thing, and we've worked with several of the manufacturers powertrain divisions to come up with solutions for these problems that don't require a total redesign of the tranny in question." "Staying on top of the "Service Bulletins" issued by the manufacturers and participating in any "recalls" that effect your vehicle are the best ways to make sure your vehicle is "current" with what the factory has to offer. Above all else though, make sure you change your fluid and filter at specified intervals, and keep the transmission in proper adjustment. That's the key to getting a long, healthy life from an automatic." Bohem had great praise for the C6… "It's almost bulletproof out the factory door. The C6 has served behind big and small blocks, passenger cars and motorhomes. It's even seen duty in some of the larger truck lines. At the same time it's just as much at home behind a 428SCJ going down the 1/4 mile. In stock form, they're pretty hard to kill, but when you build them, …well, it takes a lot to hurt'em." "We have built a lot of C6s for Prerunners and race trucks over the years and have had really good results. Internally they're full of big, beefy pieces. There's nothing "small" in a C6. Big bearings, big planetary, big gears, clutches and bands. When you consider what goes on in the tranny of an off-road race truck, they have to be big."
We've had the chance to spend a little time on and off the road with our new Valley C6 and next month we'll give you the full scoop on the process, but for now, we'll leave you with the basics… Shifting an automatic all the time takes some getting used to. Shifts break the tires loose with anything more than a minimum of throttle. "Drag race" style shifting will unweight the front suspension. This puppy grabs hard and "right now!" Downshifting early results in skidding tires. Caution is emphasized. If you need a rebuild or an upgrade for your Automatic, regardless of the manufacturer, I know a guy…..
Valley Transmission 1158 North 2nd St. ElCajon Ca 92021 Phone: 619-447-4353
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