As the number of 6.7L Cummins–equipped Rams on the road increased, so did the amount of people looking to modify them. Unfortunately, these enthusiasts quickly learned that the Chrysler 68RFE six-speed automatic transmission was the weakest link in an otherwise stout drivetrain. With as little as a programmer, the 68RFE is prone to failure by burning up the overdrive clutches. Adding much more power can cause the torque converter to fail, or worse. If you’re driving a modified 6.7L with the stock transmission, it’s not a matter of if, but when it will fail.
Fortunately, there are solutions in the marketplace ranging from performance torque converters to full replacement transmissions. Up until now, these have been relegated to people making up to about 750 hp—much more than that and you were looking at swapping in a different transmission altogether. However, with 6.7L horsepower levels creeping into four-digit territory more
frequently, the folks at RevMax felt the need to build a transmission capable of surviving this level of torture.
Enter the RevMax 68RFE Signature 1,000. RevMax builds each of these transmissions to the most stringent tolerances, with a single technician from beginning to end building each one. And when they are finished, the person who built it signs each unit. This personal touch shows just how much pride is built into every Signature transmission. To handle the extreme power it’s rated for, the Signature 1,000 includes an array of billet parts, including the input shaft, input clutch housing, underdrive and overdrive hubs, and a billet Stage 5 triple-disc torque converter. Alto Red Eagle clutches with Kolene steels are fitted inside, along with a high-pressure pump and a custom-calibrated valvebody.
We managed to get our hands on one of the first models available to the public and plan to put it to the test behind a 1,000hp 2008 Ram HD. We’ll report back soon with how it’s holding up, but for now come along with us as we take a look at what goes into building one of the toughest 68RFEs on the market, and then slap it in for some real-world testing.
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Building the Signature 1,000 begins with the teardown of a wasted core. Transmissions come in with a variety of different ailments, but never fear, all internal parts are either checked or replaced.
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Technician Jason Lampus is seen here removing the input clutch drum from the core transmission. This housing is the primary focus at RevMax, as it contains the overdrive clutches and is known as the weakest link inside the 68RFE.
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With the drum removed from the case, Lampus set to work disassembling the unit.
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This is what you never want to see inside any transmission: the stock overdrive clutches have literally welded themselves to the hub.
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Unfortunately, this is quite typical of transmissions from trucks with even a mild programmer installed. The thin clutches suffer from coning and deformation due to the increased torque they receive. Note the discoloration and beveled appearance of the factory overdrive clutches.
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RevMax utilizes five Alto Red Eagle clutches with Kolene steels, along with a custom clutch piston in the Second gear position (top) as opposed to only three in factory trim (bottom). This results in a 66 percent increase in holding strength.
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For Fourth gear, factory is again three clutches and steels (top) and is replaced by a four-clutch setup. The benefit from this is a holding strength gain of 33 percent.
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The signature 1,000 is made special with the addition of phosphate-coated steels, clutches specific to it, and custom snap rings. Made from two pieces of billet aluminum, the drums are anodized to prevent premature wear. Pressure plates are cut from solid billets, and a 300M input shaft is used.
RevMax machines all its Signature 1,000 input drums in-house. These billets start out weighing 22 pounds before being machined down to less than 3 pounds. The billet drums are the backbone of the Signature line of transmissions. Increasing the diameter of the drum is what allows for the additional surface area, which increases the transmission’s holding capacity.
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For comparison, from left to right are the different input clutches and steels used in the RevMax Signature line of transmissions. At the far left, the RevMax 550s use high-energy BorgWarner clutches, which provide 18 percent more surface area than factory. The 850s (middle) feature a wider clutch that is custom made to fit their billet drum. Finally, on the right, the Signature 1,000 utilizes custom clutches that provide a 61 percent increase in surface area.
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The input clutch drums also differ between Signature models. We see a modified OE drum used in the 550 (left), anodized billet 850 drum (middle), and the 1,000 drum (right).
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RevMax utilizes SuperFlow TCRS equipment to weld its converters. This assures a perfect weld, every time. Seen here is a set of turbine splines being welded into place on a turbine.
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The Signature 1,000 comes with a triple-disc torque converter with a billet front cover. It features a 4130 chromoly impeller hub, hardened turbine hub and splines, high-performance Torrington bearings, and a billet stator bearing cap.
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Before being installed, every RevMax Signature valvebody and pump is vacuum leak-down tested prior to being modified to increase line pressure and fix the factory flaws.
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Here we get a glimpse of a 68RFE pump mounted up to the mill, ready to receive the RevMax-specific modifications.
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A SuperFlow valvebody dyno is used to test each valvebody assembly before it is installed in the transmission. Before leaving for installation, each RevMax transmission is fully tested for hydraulic and performance integrity on an AMI hydraulic test stand.
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With assembly of the Signature 1,000 transmission complete, we headed to Bud’s Diesel in Midway City, California, to install the new slushbox. But before the new transmission could go in, the old one needed to come out. Technician Tom Pohl led the charge and had the old unit out in no time.
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The Signature 1,000 is shipped bare, meaning all the factory adapters, hoses, plugs, and brackets needed to be swapped onto the new transmission before installing it in the truck. Be careful not to miss any, as even the smallest plug can cause a big mess.
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One of the most important steps listed in the instructions is the installation of a new line pressure sensor. If this part is skipped, the warranty is voided.
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Care must also be taken when installing the torque converter, as the most common mistake during installation is a damaged input shaft seal. Pohl generously lubed the input shaft, and while supporting the heavy converter from the bottom, gently slid it into place.
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With all the required parts swapped over, Pohl positioned the new transmission in place and began the reassembly process. Once installed, the transmission must go through a regimented relearn and break-in process. Any deviation from the guidelines could result in permanent damage. However, after completing the break-in, this transmission should last a long time and handle very high power levels.
