PERFORMANCE TRANSMISSION OVERHAUL
DISASSEMBLING, ANALYZING, AND UPGRADING A BUILT E4OD—8 YEARS LATER
The built automatic transmission is a mainstay in the diesel world. At some point, even the toughest factory transmission needs to be reinforced in order to continue the never-ending quest for additional power. But, as this article illustrates, having a built automatic in your truck doesn’t mean it’s exempt from ever requiring a once-over, if not a full-on rebuild, from time to time. Although having to rebuild an “already-built” transmission is something a lot of folks don’t like to hear, in the end it’s practicably inevitable. While a performance transmission can be prepped to handle big horsepower and gobs of torque (and do so extremely well), it can’t handle the job forever—especially if you’ve added power since the last time your transmission builder was in there.
Such was the case with our E4OD: a transmission built once upon a time at John Wood Automotive. When the old-school four-speed was first put together back in 2011, it was intended for a 400-rwhp OBS Ford. Now, having added 300/200 hybrid injectors from Unlimited Diesel Performance, an Irate Diesel competition electric fuel system, and a Fleece Performance Engineering Billet S468, the same truck sits at nearly 600 rwhp. After more than eight years of trouble-free use and 70,000 hard-earned miles, the transmission had never skipped a beat. However, before pursuing further horsepower goals it was time to: 1.) Find out why the fluid was burnt, and 2.) See how well the transmission’s internals had held up over the years—especially with the near-50-percent increase in horsepower it had seen.
So, with the E4OD pulled and strapped to a pallet at Flynn’s Shop in Alexander, Ill., it made its way to John Wood’s facility in Holtville, Calif., while we caught a plane to join Wood for the tear down. Upon disassembly we discovered that, while nothing had failed catastrophically, there were some warning signs that things were about to go south. Follow along to see what components needed attention, what parts checked out just fine, and which billet upgrades Wood included in our new Street Performance transmission build.