The 68RFE came out in 2007 and typically came behind the large gas V-8’s and the large diesel engine applications and have been modified with aftermarket parts from the beginning. We all know that these motors are capable of putting out all kinds of crazy horsepower and torque.
Fast forward to 2019. Dodge/Ram is making several changes at the factory level. In this edition of Fun with Transmissions, we are going to check out the changes to the 68RFE and how they affect transmission operation. The changes are in:
- The Valve Body
- The Pump
- The Solenoid Body Addition of an Auxiliary Valve Body
First, let’s check out how the valve body has changed for reverse and underdrive clutch application and release controls. The original 68RFE hydraulic design has limited control of clutch venting for shifts out of Reverse or Drive, which leads to an excessive variation in garage shift performance.
An auxiliary valve body has been added to the lower valve body. This body contains a new reverse clutch accumulator and a new TCC solenoid (figure 1), a TCC solenoid fluid accumulator, and a new #3 checkball (figure 2). Under the auxiliary valve body is the #9 checkball in the lower valve body casting (figure 3).
Notice, in the previous models, how the reverse clutch is applied and released when the manual valve is moved into and out of reverse (figure 4). Only the #3 checkball and the R1 orifice control the amount of oil going to and from the reverse clutch.
With the changes to the valve body and the addition of the auxiliary valve body, the reverse clutch circuit gets another orifice, another checkball, and it also gets its very own solenoid (figure 5).
When the manual valve goes to reverse, the reverse solenoid is off. The #3 checkball will seat, and the apply oil will go through the R1 and R2 orifices. The #9 checkball will not be seated during the clutch apply.
When the manual valve is moved out of reverse, the #9 checkball seats and forces the oil through the R1 orifice, and the reverse solenoid will pulse to control the amount of oil exhausting from the reverse clutch apply circuit.
The addition of the orifice and the solenoid means that the computer can control the release rate for a better “shift feel.”
UNDERDRIVE CLUTCH APPLY/ RELEASE
Let’s check out the hydraulics for the underdrive clutch. On the pre-2019 valve bodies, the underdrive clutch applies through the underdrive solenoid and the U1 orifice (figure 6). Notice the #2 checkball is seated during the apply. This a more controllable setup than the reverse clutch apply and release circuit, and there needed to be more control of the release side of the underdrive clutch.
In the 2019 redesigned valve body, there is an added #8 checkball and U2 orifice (figure 7). When the manual valve is moved to the drive position, the underdrive clutch applies through the #8 checkball, the underdrive solenoid and the U1 orifice. The #2 checkball is seated during the apply. Here is where the update comes in. The addition of the #8 checkball creates an additional resistance in the circuit so that the rate of release can be controlled more consistently by the computer for a better underdrive clutch release feel.
TCC SOLENOID OPERATION
For 2019 a dedicated TCC solenoid was added. According to Chrysler, the new solenoid and revised porting will provide better torque converter slip control during the shifts. The idea here is to smooth out the bumps during the shifts.
This solenoid, like so many solenoids these days, has a bar code that will need to be programmed into the controller. PCM programming is required if the solenoid, PCM, or transmission assembly is replaced.
The PCM will need the flow-rate of the new solenoid for proper transmission performance. The wiTECH procedure requires the solenoid’s 2D barcode to be scanned using a smartphone or mobile device. The wiTECH routine refers to it as “PI Curve.” The “P” stands for pressure, and the “I” is for electrical current.
This code has a long string of numbers and letters (figure 8a). Having the scanning app on the same device as wiTECH can allow the code to be copied and pasted.
The solenoid data is encoded in the QR label located on the exterior of the new transmission assembly. This code contains the original assembly pressure curve. Scan the QR code and enter the data as required by the scan tool (figure 9).
For PCM replacement, run the “PCM Value Replacement with Value Transfer” routine. This will transfer the solenoid data to the new PCM. It is critical to upload the correct solenoid data to the PCM. Attempting to use a code from a solenoid not installed in the transmission could have catastrophic consequences.
Figures 10 and 11 show the redesigned lock-up regulator valve for the 2019 and later models; notice the TCC solenoid fluid accumulator. This accumulator valve has been moved from the pump housing to the auxiliary valve body. We can also see the addition of the A4 and A5 orifices.
In 2019 the TCC VFS solenoid was added, and the TCC regulator valve was changed. The accumulator piston and spring have been moved out of the pump and into the auxiliary valve body. The TCC solenoid, when commanded by the TCM, precisely controls the apply and release of the torque converter clutch (figure 12). Chrysler states: “The new torque converter solenoid will control slip during the shifts to reduce the potential for shift bumps.”
The solenoid body now has a blue connector and a pigtail for the TCC solenoid on the auxiliary valve body (figure 13). This solenoid body has a blue case connector and is not interchangeable with any other solenoid body.
In 2019 Chrysler made several changes to the 68RFE. These changes included adding an auxiliary valve body, adding a dedicated TCC control solenoid, and changing the TCC regulator valve. Other changes include modifications to the valve body and the channel casting for controlled reverse and underdrive venting.
The goal of these changes is to improve the park, reverse, and drive engagements and disengagements. Another goal is to improve upshift and downshift feel related to TCC control during the upshifts and downshifts. When these goals are met, the customer gets a better driving experience, and we all know that a happy customer is why we have Fun With Transmissions!