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.
| Building the Signature 1000 begins with the teardown of a wasted core. Transmissions come in with a variety of different ailments, but never fear, all internal parts are thoroughly checked, then replaced.
| This is what you never want to see inside any transmission: the stock overdrive clutches have literally welded themselves to the hub.
Enter the RevMax 68RFE Signature 1000. 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 1000 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 ’08 Ram 2500. 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.
| 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.
| 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.
| With the drum removed from the case, Lampus set to work disassembling the unit.
| RevMax utilizes five Alto Red Eagle clutches with Kolene steel, 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.
| 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.
| RevMax machines all its Signature 1000 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.
| The Signature 1000 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 1000 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.
| With assembly of the Signature 1000 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.
| 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.
| The Signature 1000 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.
| 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.
