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Ford Bronco E40D Transmission Rebuild
Orange County Transmissions Walks Us Through The Basics Of A Ford Tranny Rebuild
From the January, 2010 issue of Off-Road
By Dexter Roberts Jr.
Photography by Off Road Images
Ah, sweet salvation for The... Ah, sweet salvation for The Juice! The transmission has been thoroughly cleaned and is ready for the rebuild. The Derale Atomic-Cool transmission cooler sits in front of the tranny to the left, and to the right is the PML transmission pan. Time to get crackin'! We've been waiting for this to happen-it was only a matter of time before the overly weak stock E4OD in our Bronco went out under an overly heavy foot. We'd been getting on The Juice pretty hard. A recent engine swap and some performance upgrades had given the Bronco some kick, and it seemed like we were on a mission to kill a transmission. Finally, after a full day of high-speed hijinks on some great dirt roads up near Moab, Utah, we felt the tranny starting to go. We weren't about to stop since we were in the middle of nowhere, so we stayed in the throttle until so much white smoke poured out that we couldn't see anymore. The 140,000-mile old E4OD was history. Pro Torque produces a dizzying... Pro Torque produces a dizzying array of converters that can be matched to pretty much any application. We think our Bronco's stock stall speed was somewhere in the 1,800- to 2,000-rpm range prior to the rebuild. This performance converter has a stall speed somewhere near the 2,200-rpm level. Pro Torque also produces custom converters for tricky or super-high performance applications. We were able to get the vehicle back to SoCal, and into one of the best transmission shops we know of, Orange County Transmissions. After some investigation, it was determined that a small fluid leak had eventually left the Bronco's E4OD transmission devoid of ATF, which had doomed it, though we're pretty sure our driving didn't help matters either. We had broken transmission rule number one (which dictates that transmission fluid should be checked before and during long, taxing sessions of driving). The gang at OC Transmission tells us that a great many transmission failures can be avoided by following this simple rule. A rebuild was in order, and we continued to hang around the shop to learn what this would involve. Being that we willfully admit we like to abuse our vehicles, transmission temperature is always a concern. In fact, the OC Transmissions crew told us that insufficient cooling is another big transmission killer. Derale Cooling Products came to our aid, providing us with their Atomic-Cool external transmission cooler, which included an electric fan to further enhance its abilities. Being that we hammer The Juice... Being that we hammer The Juice pretty hard and heat is a transmission's worst enemy, we wanted to make sure we used an external, remote-mounted transmission cooler. Derale hooked us up with this great Atomic-Cool unit. An electric fan attached to the cooler further enhances cooling capabilities. The unit looks very similar to a small radiator. The torque converter is an essential rebuild component. It acts as a fluid coupler that transfers power from the engine to the internals of the transmission. It also allows the engine to remain running at rest without stalling, like a slipping clutch. When bolted to the engine's flywheel, a converter actually multiplies the torque provided, and transmits movement (rotation) into the transmission itself. It is the torque converter that determines a transmission's stall speed, the point at which (when a foot is held on both the gas and the brake) the vehicle's tires start spinning or the engine's rpm level will no longer increase. Higher stall speeds mean a vehicle can be launched from a braked position at a higher rpm, thereby allowing the engine to quickly reach and stay within its peak horsepower range. With this in mind, Pro Torque provided us with a torque converter with a slightly higher stall speed than stock. Other parts common to transmission rebuilds include bearing kits, new clutches and seals, clutch housings, snap rings, and a reprogramming kit-all of which we needed. TransGo provided the reprogramming kit (sometimes referred to as a "shift kit," although that term is actually the brand name of B&M's reprogrammer line, rather than a generic term), which will provide us with faster, firmer shifts, thereby reducing slippage and keeping the vehicle's power to the wheels. And PML provided us with a really nice finned aluminum transmission pan that allows more fluid capacity and some other perks. PML provided us with this... PML provided us with this transmission pan for the rebuild. It features an increased oil capacity, aluminum construction, a magnetic drain plug, a black powdercoated finish, and exterior fins to help alleviate high temperatures. Thick walls and a machined gasket surface combine to make this one tough, leak-free tranny pan. If this sounds like a lot of parts and components to you, you're right, and OC Transmissions tells us that the casual off-road enthusiast probably shouldn't just crack into a transmission without prior experience. For one thing, specialty tools are required during the rebuild process. Also, a tiny mistake in measurement or clearance can cause major damage. Still, it's handy to know what's involved in such a rebuild, and with just a little knowledge, it's possible to dictate the specifications you'll want to match a rebuilt transmission to its host vehicle. Plus, if you have a general understanding of how a transmission works, you're less likely to be taken to the cleaners by an unscrupulous tranny shop (this is also why it's good to find a respected, experienced shop like OC Transmissions). We held our camera as the experts at the shop rebuilt The Juice's tranny and explained it all to us. Check out the photos to see the primary steps of a transmission rebuild.  Here, the rebuild is about...  Here, the rebuild is about to start. The gang at Orange County Transmission was eager to get started, and we did our best to stay out of the way. The blue box houses the Transgo Reprogrammer Kit, which will cause the transmission to shift more quickly and firmly. The aluminum planetary gears are also visible; our E4OD utilizes a four-pinion setup, although some HD trucks (as well as the Ford Lightning) use six-pinion gears. |  While at Orange County Transmissions,...  While at Orange County Transmissions, we heard it more than once: "cleanliness and clearances are the keys to a proper rebuild." Here, a gauge helps to check clutch pack clearances, as other rebuild components rest on a spotless work table. |  Here, the sprag is assembled....  Here, the sprag is assembled. This component (a one-way freewheel clutch) allows the transmission to smoothly change gears under load. |  A press is used to insert...  A press is used to insert the bushings into the overdrive drum. As the rebuild progressed, a number of shop and specialty tools were utilized. This is important for the do-it-yourselfer to realize, as it would be quite a mess to attempt a rebuild without the proper equipment. Consider that your warning, and feel free to email us photos of any unsuccessful rebuild attempts-we'd love to see 'em. |  Here, the stator is placed...  Here, the stator is placed into the two-piece pump. The stator uses the kinetic energy of the moving transmission fluid to further multiply torque. |  Here, the case bushing is...  Here, the case bushing is driven into the transmission. Our original case bushing was a two-piece unit, but we've opted to go with a one-piece for this build, which should last longer. Hey, less parts to break, right? |
 Here, the rear gear train...  Here, the rear gear train is visible in the transmission's housing. It must be assembled while the transmission is standing up on its end. While it would take an entire book (or a volume of books) to explain the function and assembly of every part within a transmission, learning the basic parts isn't too difficult and can be extremely helpful when repairs are needed. |  The completed transmission,...  The completed transmission, with the input shaft visible. Our Orange County Transmission-built E40D is ready to be mounted in our Bronco. |  These guys are our new heroes....  These guys are our new heroes. Seriously, finding an honest, experienced, and extremely knowledgeable transmission shop such as Orange County Transmissions is like finding a pot of gold at the end of a rainbow. Jason, Rob, and Dave are enthusiasts who build bad-ass transmissions (or tame stock-y ones, if that's what is called for). Thanks to their help and expertise, The Juice is ready to hit the dirt again. |
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