The 45RFE, 545RFE, 65RFE, and 66RFE automatic transmission for Jeeps and Rams
In June 1998, Chrysler introduced the innovative 45RFE in its 1999 WJ Jeep Grand Cherokee. Produced at Chrysler's Indiana Transmission plant in Kokomo, it was paired with the 4.7 L PowerTech V8 engine. The 45 number refers to the torque rating (5) and number of forward gears (4); RFE refers to rear wheel drive application and full electronic controls.
The 45RFE automatic transmission in the WJ featured three planetary gear sets instead of the two usually used in a 4-speed automatic; and it included three multiple disc input clutches, three multiple disc holding clutches, and a dual internal filter system (one which was a primary filter for transmission sump, the other for the fluid cooler return system). Four forward gears were used in normal acceleration, with a different second gear used to increase versatility in “kickdown” acceleration. Despite using five forward ratios, Chrysler played it safe and decided to call it a "4-speed automatic."
At the time, Chrysler boasted its tall 3.00:1 first gear for better initial acceleration; and noted that while the standard second gear was 1.67:1, the kickdown second was 1.50:1, for smoother downshifts. Reverse gear was equal to the first gear to accommodate heavy loads. At the time it was launched, it had the widest range of gear ratios in its class; its factory was brand new at launch.
Five speeds: the 545RFE transmission
In 2001, with programming changes and an extra, taller overdrive ratio, the 545RFE was born. With the change to overdrive, cruising at 70 miles per hour (110 km/h) with a standard axle ratio would yield 2000 rpm at the engine, about 200 rpm less than the 45RFE, cutting fuel consumption and noise.
The 545RFE’s engineering reached back to the rock-solid Torqueflites, but it incorporated many contemporary innovations and practices. The six-speed transmission was programmed to act as a five-speed with an alternate second gear for downshifts.
During a recent live Q & A chat session with Washington Post automotive columnist Warren Brown, who has covered the car industry since 1982, we asked him about the importance of having the extra gear and whether it's a big selling point for buyers.
As to the question of why the 545RFE has two overdrive gears that are so close to each other, engineer Bob Sheaves noted that size is an issue with planetary gears; most likely, the top 0.67:1 ratio gear was chosen because that was the largest one that could fit into the available space, without requiring changes to the design of the Jeeps and trucks using the transmission.
When towing (in some vehicles), a “Tow/Haul” mode provided crisper shifts to cut wear on the transmission, and reduced gear searching by holding lower gears longer. The system also selected lower gears when going downhill, to use the engine’s braking capability. In 2006, Chrysler claimed that the transmission had been “refined for higher-quality shifts;” it was strong enough to give the Jeep Commander and Grand Cherokee class-leading towing capacity of 7,200 lbs. The changes included a redesigned solenoid to provide quieter operation when shifting (ending “solenoid clatter”), and a turbine damper to cut noise and vibration from the torque converter.
Used in Chrysler's fleet of rear-wheel drive trucks, including the Jeep Liberty, Dodge Ram, Dodge Dakota, Dodge Durango and Jeep Commander over the past decade, the 545RFE is sophisticated, multi-ranged, and electronically controlled by a Transmission Control Module (TCM). Its shiny bellhousing -- a one-piece die-cast aluminum casing -- resembles a rocket ship designed by NASA engineers.
The 545RFE combines optimized gear ratios for responsive performance, including maintaining speed on long or high grades, without sacrificing efficiency at highway speeds; efficiency features including variable line pressure; and it has a low NVH (noise, vibration and harshness) thanks to ribs integrated into the case that increases multi-angular torsional rigidity.
The 545RFE is equipped with dual lubricant filters, including an internal main sump pan filter and an external canister-type pump return filter. The fluid capacity for service refill is 6.55 quarts (6.2 liters) and its fluid type is Mopar ATF +4. (Earlier units were specified as taking ATF+3 but ATF+4 is a superior fluid which can substitute for ATF+3).
Despite its steady improvement over the years, the 545RFE isn't without fault, and critics sometimes complain about its choice of gear ratios. While the 545RFE, as used in Ram trucks, may not perform as well as its Ford counterparts for unloaded acceleration, the 545RFE keeps running when the Ford runs out of reserve torque rise; it’s better suited for high loads and steep grades. The transmission is well suited for the large torque band of the Hemi V8, as well as previous engines it and its predecessors were used with. (The 545RFE has been used with numerous engines, including the 3.7 V6, 4.7 V8, 5.7 V8, and VM 2.8 diesel).
In 2009, modifications were made to the 545RFE that enabled drivers to select the highest gear the transmission would shift to, which has proved a helpful feature for towing, hill climbing, and hill descent.
With the 545RFE, Chrysler has equipped its trucks with a smooth and responsive rear-wheel transmission, one that requires few repairs. A six speed version joined the lineup in 2012; in addition to using all gears in normal acceleration rather than reserving one for kickdown.
Six speeds: 68RFE and 65RFE automatics
The 545 RFE was the basis for three six speed automatics. First out of the gate was the 68RFE, a six-speed, heavier-duty automatic. The 68RFE was created essentially by using a similar clutch and hydraulic control system, with different planetary gears and tooth counts; numerous parts, including the various shafts and clutches, the gears themselves, and the torque converter, were redesigned to handle the high torque of the Cummins 6.7 liter diesel. Pump capacity was increased to deal with heat more effectively.
Designed to work with the Cummins engine, the 68RFE has a lower first gear than the 545 for better launches and a wider spread, overall, of ratios. The torque converter clutch is engaged in every forward gear but first, based on factors such as temperature, gear, tow/haul mode, exhaust brake activation, etc. The transmission was designed to include electronic range selection. Because it uses a unique computer, it cannot be retrofitted back into earlier trucks. The assembly weighs 263 lb.
The next six speed derived from the 545RFE was the 65RFE, used with V8 versions of the Ram 1500, Durango, and Grand Cherokee. The 65RFE only has six forward gears in ERS/AutoStick mode or kickdown mode; it is essentially a software and name change, which allows people to reach the “prime” gear via ERS as well as than kickdown. An internal Chrysler communiqué to dealers summarized the change in a similar fashion.
The 66RFE is a new transmission based on the same basic core as the 545RFE. It is similar to the 68RFE in basic construction, but differs in duty rating; for some of the possible differences, see the 68RFE page. Gearing is identical to the 68RFE.
* On 545RFE, 3rd is only accessible via kickdown in some situations, and is referred to as “2 prime.”
On 65RFE, 3rd is only accessible via kickdown in some situations and use of manual override.
** Chrysler specified a 2.21:1 reverse gear in some applications, including the Jeep Liberty diesel.