The 545RFE uses three planetary gear combinations for added durability that drops the First gear ratio a little deeper with a 3.00:1 low gear, a 1:1 fourth gear, and Fifth gear at 0.67, which is a substantial 33 percent overdrive. This trans can also be found in Dodge Durango models from this time period. The 545RFE is found in a wide variety of truck and SUV applications from 2001 to 2012 with Jeep Grand Cherokee and Jeep Commander models sporting the higher output Hemi engines. We’ll concentrate on the five-speed version for this story as it was used behind the more powerful V8 Hemi engines. Predating the 545RFE was the 45RFE that was a four-speed box that was normally paired with the smaller 4.7L V8 engines. The RFE suffix tells us that this is one of the early Chrysler gearboxes to exert full electronic control for a rear wheel drive vehicle. This next evolution in Mopar automatics expanded the four-speed concept in 2002 in Dodge Rams, Durangos and other vehicles by extending gear multiplication to five forward speeds. Note: 545RFE four-wheel-drive application pictured. The shift into overdrive is controlled electronically along with engagement of the torque converter clutch.īecause this transmission can be built to take quite a bit of abuse, it’s a reasonable choice as a swap both for all Mopar engines but especially behind a Gen III Hemi since Holley now offers the ability to control fuel injection with the affordable Terminator-X Max ECU that can easily manipulate the electronic side of the 46RE transmission with the adition of this adapter harness ( 558-473) This TV input establishes both load and mph-based shift points related to the position of the TV cable. The 46RE uses hydraulic control for the 1-2 and 2-3 shifts based on position of the throttle valve (TV) cable connected to the throttle body. Combined with a lockup converter, this would make an excellent street transmission. This makes for a great highway combination since this 31 percent overdrive will soften a 4.10:1 rear gear down to the equivalent of a 2.82:1 rear gear ratio. The 46RH and 46RE both use the same gear spread as the old A727 but with a 0.69 overdrive. In its previous iteration, the 46RH was found in earlier vehicles from 1990 through 1998. The 46RE can be found in a number of different rear wheel drive Chrysler products from 1995 through 2002, and some early-production 2003 Dodge Ram pickup trucks that had the 5.9L Magnum V8. This transmission employed what can best be described as partial electronic control over the transmission. The next in this evolution was the 46RE, which is essentially electronic control over the previous 46RH or hydraulically controlled 727. These later transmissions featured an overdrive placed in the extension housing. The A727 briefly morphed into the A518 that then evolved into what became the 46RE that we’ll discuss next. These are an affordable overdrive transmission for stock small-block applications. Then came the 42RE and 44RE versions that were electronically controlled. The A904 was also called the A500 for awhile and then rebranded again into the 30RH, 36RH, and then to the 40RH/42RH designations that were hydraulically controlled and used in 1990’s Jeeps and light duty trucks. We’ll just briefly mention the A904 transmission here as the majority of the late-model transmission swap interest will be with the higher capacity transmissions. This was necessary because the earliest electronic efforts were aimed solely at adding an electronically controlled overdrive to the existing A727. Most of these are self-explanatory except for perhaps the difference between E as electronic and FE as full electronic. We’ve included a chart that defines all the alphanumeric abbreviations in an attempt to make this a bit less baffling. Using this concept, you begin to see how the A727 can be called a 36RH or 37RH with increased torque capacity. The 3 represents the number of forward gears, the 0 is the lowest rating in torque capacity, the R is for rear wheel drive, and H means the transmission is hydraulically controlled. So with the new orientation, the A904 became known as a 30RH. If you think about it, the term A904 is not really that informative. Much like what other OE’s have done, the engineers began this evolution by renaming transmissions with a new system that still uses letters and numbers but in a more efficient fashion. These transmissions should be familiar so we’ll start with them. This trans used a 2.54:1 First gear ratio.Īll Mopar fans know about the original three-speed automatics like the aforementioned A904 and A727. Among the original Mopar three-speeds is the venerable A727 automatic that was used behind some fairly strong RB big-blocks like the 440 wedge and the 426 Gen II Hemi.

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