Chrysler’s 45RFE transmission, launched in 1998, used three planetary gear sets instead of the normal two being used at the time. The transmission later evolved into Chrysler’s first diesel specific transmission, the 68RFE, which was introduced alongside the 6.7L Cummins turbodiesel during the 2007 model year with the Ram and Pickup Lines. The newer transmission design provided the benefits of modified internal components to handle the increased torque and revised gear ratios for larger applications. Monster provides a wide variety of different builds for this transmission for additional ratings of horsepower and torque. These include the Heavy Duty, Super Duty, and Super Duty Xtreme models of Dodge Ram trucks.
The transmission’s band-less design and upgraded filtration system have proved to be significant improvements over previous transmissions, allowing for extended time between service intervals, while also reducing service costs. Under partial throttle, shifting into gears above third was delayed; and the system was likely to kick down under part throttle into fourth and fifth. A new Tow or “Haul” mode allowed for faster and crisper shifting in order to reduce engine wear, while still allowing overdrive unless the driver has previously locked it out. The 68RFE transmission was the biggest leap forward in terms of Dodge automatic transmissions since the inception of the Dodge Cummins power plant.
In the past, four-speed transmissions were the weak link for the vehicle’s powertrain. And while the 68RFE has proven itself in many respects, it has also shown plenty of weaknesses, as well. As power is increased above stock, heavy loads are hauled, and miles are racked up, the 68RFE’s are failing, partly due to the electronically controlled nature of these transmissions. The 66RFE was introduced in 2012 as a lighter-duty version of the 68RFE, with the main differences between the transmissions being in the torque converter.
The 68RFE kept the basic clutch and hydraulic control design, matched with heavier-duty planetary gears, toothed differently to increase their capacity. The shafts, clutches, pump, torque converter, and other parts were also redesigned to handle the Cummins 6.7 liter diesel. The 263-pound 68RFE has roughly the same torque capacity as the Aisin automatic option in Ram heavy-duty pickups, but the Aisin allows for a power takeoff (or PTO), while the 68RFE does not; the Aisin also had a steeper first gear for better off the line power, with the same sixth gear ratio.
The processes involved to build more robust replacement parts has been tedious for the aftermarket manufacturers. However, with several years, and many miles under their belts, most of the manufacturers have determined the best methods to manufacture “bulletproof” replacement parts, leaving a wide selection of proven parts now available.