The Dodge 47RH and 47RE heavy-duty automatic transmission
A heavy-duty four-speed Torqueflite® transmission designated 47RH was used on Ram 2500 and 3500 models with 8.0-liter V-10 or 5.9-liter Cummins Turbo-Diesel engines. It had a torque capacity of 450 lb-ft and supported trailer towing capacity up to 19,000 pounds GCWR - the highest ratings in the industry for a one-ton truck. The 47RH included a torque converter with lock-up clutch, a hydraulically operated three-speed planetary transmission, and an electronically-controlled overdrive unit. Overdrive could be locked out with a button.
The 47RH transmission was created by upgrading the 46RH transmission and the overdrive unit. Base transmission revisions were:
- Input shaft enlarged 0.070-inches at the torque converter clutch oil feed hole
- Torque converter clutch oil feed hole shot-peened inside
- Pressure angle on spline between the intermediate shaft and the front planetary gear unit changed from 37.5 degrees to 30 degrees
- Fifth pinion added to the front planetary gear carrier
- Reverse band widened and changed from single to double wrapped configuration
- Reverse servo unit revised
- Case casting and machining redesigned to accommodate internal changes noted above
Overdrive unit revisions included the following:
- Ninth disc added to overdrive direct drive clutch
- Output shaft governor shaft cross hole shot peened to increase fatigue life
- Output shaft selective annealing process revised to allow governor shaft cross hole to remain hard
- Governor drive key changed from semi-circular "Woodruff" to a 1/ 4-inch square to reduce stress on the shaft
As with previous Dodge truck automatic transmissions, a switch on the instrument panel allowed the driver to lock out overdrive when carrying or towing heavy loads.
The torque converter clutch engaged at highway cruising speed to improve fuel economy. The converter clutch was not previously available with the diesel engine. The V-10 and diesel versions of the transmission had unique shift schedules due to their vastly different torque curves.
The 47RH was replaced by the 47RE. (The 4 was the number of gears, including an overdrive; the capacity rating of 7; R for rear wheel drive; and H for hydraulic control, or E for electronic control, though the substitution of “E” for “H” was more of a coding change than an engineering change). The primary difference between the two automatics appears to have been the name, since Chrysler press materials noted that even the 47RE had hydraulic shift control (other than the overdrive, which was electronically activated in both automatics).
The 47RH and 47RE were reserved for V10 and Cummins diesel engines.
Overall Top Gear Ratio: 2.57 with 3.73 axle ratio and 2.82 with 4.10 axle ratio