Inside AFE’s New Torque Converter

It’s pretty common that the first performance upgrades diesel owners make to their trucks are in the form of a cold air intake, high-flow exhaust system and performance programming of some kind. While these three modifications can really breathe new life into a truck, the weak link in the chain with all this newfound power becomes the transmission. While the Big Three have made major improvements in automatic transmission technology and performance in recent years, holding up to 850 lb/ft of torque in stock trim in their newest diesel offerings, there’s always room for improvement on a modified truck.

AFE Power of Corona, California, is one of these aftermarket companies always on the edge of leading technology and performance products that can improve upon OEM equipment. AFE Power has recently released their new F3 torque converter for 1994-13 Ford Power Stroke, 1994-13 Dodge Cummins and 2001-13 GM Duramax applications.

What’s A Torque Converter?

While the science behind an automatic transmission torque converter can get quite extensive and confusing to most, it’s basically nothing more than a fluid-coupling device that connects your truck’s engine to the transmission. With the engine running, but the wheels not turning, without a torque converter your motor would stall as the load and strain on the engine would be too much. So the torque converter allows for the engine/crankshaft to continue rotating while the vehicle is stopped. Yet once it starts moving, the converter uses fluid to convert that engine’s rotation and energy to improved forward/backward vehicle motion. Once up to a specific engine rpm or speed, the converter clutches can lock and turn the converter into basically a solid shaft to transfer that power, then unlock once the vehicle drops below a specific rpm or speed.

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Why Upgrade?

While the OEMs have done amazing things with factory transmissions over recent years, older model diesel trucks and even the latest 2013 models can see some benefits from the right torque converter upgrade. Most factory torque converters use a simple single-disc clutch design, which is sufficient for stock power levels. But once performance tuning, bigger injectors and turbo upgrades come into the mix, converting all that additional power to forward momentum can become troublesome for the single-disc design. In short, the clutch faces just aren’t strong enough to transfer the power efficiently and they’ll begin to slip, which raises fluid temperatures and hurts performance.

The AFE Power F3 uses a state-of-the-art, triple-disc design that not only increases the converter’s “holding” capacity, but can limit that fluid temperature rise (the number-one killer of automatic transmissions) and increase the truck’s fuel efficiency and drivability. AFE has also done extensive testing with different converter “stall” speeds, which is when the max rpm at which the converter can spin while the tires aren’t moving. While most OEM converters stall around 2,000 rpm, in some applications a lower stall can improve off-the-line performance and power transfer, which is extremely beneficial in towing applications.

However, in some applications (large turbos that like more engine rpm before creating boost) a higher stall may be preferred. Developed specifically for mildly modified daily drivers and towing applications, the F3 comes with a low 1,200-rpm stall speed, which maximizes daily driving and towing needs for stock turbo vehicles. The lower stall allows the converter to more efficiently convert the engine’s energy into forward momentum. The F3 stator has also been upgraded to a one-way sprag clutch, which improves torque multiplication and stall speed.

DW-1406-AFE-2 — 1 Obviously the first step to this project is getting the truck in the air. While the transmission can be removed from the truck on the ground, that’s a big task as they aren’t light. This installation is going to be best suited for a qualified shop with the proper tools for this kind of job. While it’s something a shade tree mechanic could accomplish, it should be just a one-day job for a professional repair shop.

Other changes made inside the F3 converter include the use of a Torrington thrust bearing for increased strength over factory plastic bearings. The torque converter’s front cover is also upgraded to a custom-machined billet cover that helps eliminate ballooning of the cover under extreme heat and in high-torque situations. This billet cover also allows for precise machining for optimum clutch fit and wear. Turbine fins are brazed for improved strength and durability under heavy abuse from heat and torque transfer. Lastly, since the triple-disc clutch design offers so much added clamping force in comparison to the OE single-disc design, damping springs are used inside the clutch assembly to ensure a smooth transition during lockup, which can improve acceleration and the overall driving experience.

Installation And Results

For testing, the F3 torque converter was installed in a mildly modified 2006 Dodge Ram 2500 with just 80,000 miles on the odometer and a stock 48RE transmission. While the factory transmission had been taken care of, it had shown some signs of slippage under heavy towing situations, so it seemed a great candidate for the converter upgrade. Equipped with an AFE cold air intake and a custom EFILive performance towing tune, horsepower levels are expected to be in the 400-hp and 800-lb/ft of torque range, well above the factory levels. The truck was also running some slightly larger wheels and tires, which put some additional strain on the power train due to the additional rotating weight. Before installation of the F3, an Edge Insight CTS was used to record some 0-60 mph runs to use as a baseline. AFE Power claims a 0-60 mph improvement of 0.7 seconds with the addition of an F3 torque converter.

DW-1406-AFE-3 — 2 With the truck up on the two-post lift, the drivelines would be the first pieces to be removed. Our test truck is a 4×4 model, so the rear driveline has four bolts on the axle end to be removed and is just a slip yoke where it meets the transfer case. There’s also a support carrier to be removed from the bed with two bolts and the entire driveshaft can be set aside. (Now would be a good time to check and replace U-joints if needed.) The front driveshaft just needed to be unbolted from the transfer case and could be swung to the side and held in place with a bungee cord.

DW-1406-AFE-4 — 3 This 2006 Ram Mega Cab has just 80,000 original miles, but it’s proved to be more than enough to wear out the original output seal on the back of the transfer case. A quick trip to the local auto parts store and a new replacement seal can be installed before the driveshaft is reassembled under the truck when it goes back together.

DW-1406-AFE-5 — 4 After removing the driveshafts, it was time to remove the torque converter bolts. On the 2003-07 5.9L Cummins trucks, there’s a small access cover on the passenger side of the bell housing adaptor. After removing the cover, you’ll have perfect access into the factory converter bolts. You’ll remove one, and then rotate the motor until the next bolt appears through this port.

DW-1406-AFE-6 — 5 To rotate the engine and torque converter to access all the bolts, a long-handled ratchet slid up between the fan shroud and engine damper can be used. Basically, just use one of the damper bolts to help turn the crankshaft slowly until you see the next converter bolt appear through your access hole.

While a torque converter swap doesn’t require any modifications be made to the transmission, it’s still a rather labor intensive job and best suited for qualified shops with trained technicians. Pulling the big 48RE automatic transmission from the truck is going to require a truck hoist, transmission jack, and other various specialized tools. Depending on the application and mechanic’s skill level, this can be anywhere from a three- to eight-hour job. It should also be noted that now would be an opportune time to have the driveshaft U-joints, output seal, and transmission fluid and filter checked and changed as needed. AFE Power strongly suggests filling the converter and transmission with fresh fluid per the vehicle’s specifications; this will ensure you can keep the warranty they offer with every F3.

After a few hours on the hoist, the test truck was now equipped with the F3 triple-disc converter, and after filling and checking fluid levels it was time for the first test drive. Within just a couple miles of driving, the owner reported a much crisper and precise shift strategy with smoother power transfer and cleaner acceleration. Running the transmission through the gears and converter lockup showed real “seat of the pants” improvements around town and under hard acceleration on the freeway onramp. Follow-up 0-60-mph runs showed closer to a full second drop, which proves the additional power transfer. While nothing was done to the truck to actually increase power, the new F3 converter was much better at getting the engine’s power to the ground. After a few weeks of driving, the owner’s also reporting a mild increase in fuel mileage (again from the improved efficiency) along with much better towing manners. DW