The term "bigger is better" echoes in the minds of most diesel owners and usually goes hand in hand with making more horsepower and torque with their truck. Unfortunately, when the factory automatic transmission fails to handle the extra power, the owner has two choices: remove the power adders and start over with a fresh or remanufactured transmission, or upgrade to a stronger transmission and keep the power coming. Most choose the latter. In the age of built automatic transmissions with billet input shafts made from 300M alloy steel, triple-disc converters with billet front covers, and state-of-the-art transmission control modules, it's easy to get carried away when upgrading your diesel workhorse's slushbox. And if you're not careful, you could spend a lot of money on a transmission that doesn't fit your needs, or perform how you want it to. It's important to convey to your transmission builder exactly what components you want and how you plan to use your truck. After all, do you really want neck-snapping shifts capable of handling 1,200 hp in your 400hp daily driver? Would you want your 400hp truck shifting hard enough to snap input shafts or other driveline parts? We don't think so. We recently stopped by John Wood Automotive in Holtville, California, where Wood was in the middle of addressing a rough shifting concern on an E4OD-equipped Ford F-350. He's a firm believer that beefed-up automatics don't have to make harsh shifts in order to be reliable or efficient-especially if the truck is only making 300 to 350 hp. Such was the case here. Read on to see how easy it was for Wood to smooth out the transmission's shifts, while still keeping them firm enough to handle the power. John Wood (above) has been working on Ford transmissions for more than 25 years. He's earned a reputation for building some of the best Power Stroke transmissions money can buy. After one quick testdrive of a customer's truck (with an aftermarket E4OD transmission), his experience told him he'd only have to perform valvebody work to address the truck's hard shifting. Specifically, the accumulator body in the valvebody was all that needed to be removed. The reason for only needing to re-work the accumulator body was because, during the testdrive, the truck's lockup shift wasn't as brutal as its First gear to Second gear (1-2) shift, Second gear to Third gear (2-3) shift, and Third gear to Overdrive gear (3-4) shift. Had the lockup shift been rough, according to Wood, it would've meant the transmission pump's inner diameter was modified (and made too large) by the transmission builder. John Wood (above) has been working on Ford transmissions for more than 25 years. He's earn Wood told us it's important to be careful when removing the accumulator body and added that if the gasket behind it is stuck, it's usually a sign that the transmission has gotten hot (which was not the case here). The easiest way to remove the accumulator body is to loosen each bolt and let it hang a few minutes to drain, and then remove the bolts and lower it slowly. Wood told us it's important to be careful when removing the accumulator body and added tha With the accumulator body cleaned up, Wood began to change its internals. The first component discovered in the valvebody was a 0.427-inch line pressure modulator valve and sleeve (only the sleeve is shown), which is used to increase fluid pressure to the clutches. This type of accumulator body modification works well without aftermarket computer tuning, but in this customer's case, the truck had a custom chip that increased the transmission line pressure as well. The combination of the two caused the owner's harsh 1-2 shift complaint. Wood replaced it with a stock-diameter (0.372-inch) line pressure modulator valve and sleeve to smooth out the 1-2 shift. With the accumulator body cleaned up, Wood began to change its internals. The first compon Next, the aftermarket accumulator control valve (also known as a capacity valve) and its shims were removed (arrows). Then, the accumulator control valve was reinstalled without the shims, which were causing the customer's harsh 2-3 shifts. To fix the hard 3-4 shift, Wood removed the aftermarket accumulator control valve and replaced it with a custom unit for a firm, yet softer shift. Next, the aftermarket accumulator control valve (also known as a capacity valve) and its s The last modification Wood made to the accumulator body was swapping out the transmission builder's accumulator springs for a set from TransGo. Wood told us that when he builds a transmission, different components from TransGo and Sonnax are used to tailor the shift quality to his liking. Throughout the years, he's concluded that, in this particular case, the TransGo accumulator springs provide the best end result for the given situation (muffling down the hard shifts). The last modification Wood made to the accumulator body was swapping out the transmission With the problems in the accumulator body addressed, it was reinstalled in the valvebody. Wood torqued each bolt to the recommended 100 in-lb, starting from the middle and working his way out. After that, the transmission pan was reinstalled, the truck's transmission fluid level was topped off, and Wood took us for a testdrive. The result was a transmission that shifted smooth and quickly. With just an hour's worth of work, he solved the truck's violent shifting mannerisms and gained another satisfied customer. With the problems in the accumulator body addressed, it was reinstalled in the valvebody. SOURCES John Wood Automotive 366 Maple Avenue Holtville CA 92250 760-356-9421 http://www.jwtt.com By Mike McGlothlin Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!