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45/545 RFE Transmission Overview

18K views 13 replies 7 participants last post by  916Timmy 
#1 ·
The 45/545 RFE transmission has been around for nearly 10 years now but there still seems to be some mystery surrounding it. Below is a brief description of how it works and the gear ratios.


The 45RFE/545RFE automatic transmissions is a sophisticated, multi-range, electronically controlled transmission which combines optimized gear ratios for responsive performance, state of the art efficiency features and low NVH. Other features include driver adaptive shifting and three planetary gear sets to provide wide ratio capability with precise ratio steps for optimum driveability. The three planetary gear sets also make available a unique alternate second gear ratio. The primary 2nd gear ratio fits between 1st and 3rd gears for normal through-gear accelerations. The alternate second gear ratio (2prime) allows smoother 4-2 kickdowns at high speeds to provide 2nd gear passing performance over a wider highway cruising range.
The hydraulic portion of the transmission consists of the transmission fluid, fluid passages, hydraulic valves, and various line pressure control components.
The primary mechanical components of the transmission consist of the following:
  • Three multiple disc input clutches
  • Three multiple disc holding clutches
  • Five hydraulic accumulators
  • Three planetary gear sets
  • Dual Stage Hydraulic oil pump
  • Valve body
  • Solenoid pack
The Transmission Control Module (TCM) is the “heart” or “brain” of the electronic control system and relies on information from various direct and indirect inputs (sensors, switches, etc.) to determine driver demand and vehicle operating conditions. Depending on the vehicle configuration, the TCM may be a standalone module or it it may be housed along with the Powertrain Control Module (PCM) in a single module. With this information, the TCM can calculate and perform timely and quality shifts through various output or control devices (solenoid pack, transmission control relay, etc.).

45 RFE gear ratios:

1st 3.00:1
2nd 1.67:1
2nd prime 1.50:1
3rd 1.00:1
4th 0.75:1
Reverse 3.00:1

545 RFE gear ratios:

1st 3.00:1
2nd 1.67:1
2nd prime 1.50:1
3rd 1.00:1
4th 0.75:1
5th 0.67:1
Reverse 3.00:1
 
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#2 ·
So if I'm reading this correctly, the 45 and 545 are basically the same, with the 545 adding the 2nd OD at .67:1 ?
 
#3 ·
Great info, thanks Remerson!!
 
#5 ·
I have to wonder about something that i have seen displayed
I can come to a stop, pull the shifter towards me & a 1 is displayed, push the shifter away from me & a 2 is displayed, same with 3, 4, & 5, then I push away one last time & nothing is displayed, what gear am i now in ?? 5th Over ??
 
#7 ·
Just an observation, when I use manual shifting mode....which is normal so I can keep MDS off without using Trail Tow mode -

If I leave the display showing '5', it shifts as 1, 2, 3(dir), 4, 5

If I manually shift through the gears, with the EVIC display showing the gears, I get a very small rpm change between 2 & 3 on the display, and all subsequent gears run a higher than expected rpm. Then after hitting 5th (as displayed), one more shift takes me out of 'manual shift' mode, and I get an additional shift to an expected rpm for 5th. It's as if it is shifting through all 6 in sequence.

Like I mentioned in the other thread, this not a complaint, but an observation. Would you consider this to be expected results?
 
#9 ·
I suspected that the converter can go into lockup in all but first gear and found confirmation in the service info.

In a standard torque converter, the impeller and turbine are rotating at about the same speed and the stator is freewheeling, providing no torque multiplication. By applying the turbine's piston and friction material to the front cover, a total converter engagement can be obtained. The result of this engagement is a direct 1:1 mechanical link between the engine and the transmission.

The clutch can be engaged in second, third, fourth, and fifth (if applicable) gear ranges depending on overdrive control switch position. If the overdrive control switch is in the normal ON position, the clutch will engage after the shift to fourth gear. If the control switch is in the OFF position, the clutch will engage after the shift to third gear.
 
#11 ·
Thanks for the info Randy. I will try to be more observant of what it is actually doing. Being a standard trans person, I find everything automatic to be quite foreign. Have to get used to the fact that I don't necessarily know what gear I'm in....and for most purposes, I don't need to know that...just gotta break old habits!

Now if I could just get the clutch fixed! Every time I step on it, there's a funny grinding sound from under the truck and my face moves quickly toward the windshield....thank goodness for seat belts! :smileup:
 
#12 ·
Good info there Randy, thanks for posting this! :)

- Cajun
 
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