Prevent RFE, RH/RE Converter Failure: Maintain Proper TCC Apply Pressure

Maintaining proper TCC apply pressure in Chrysler RFE and RH/RE series transmissions is critical, as excess pressure can cause torque converter/component damage, ballooning and converter failure. Unfortunately, these units lack the ability to limit converter apply pressure during full apply situations. To limit the amount of pressure applied to the converter, replace the OE valve with a Sonnax TCC “apply limit” valve. It’s an ideal way to improve reliability in any rebuild without affecting line pressure or creating partial apply drivability issues.

We all want to build a transmission that lives a long life, and we do our best to take the right steps to match the transmission build to the use of the vehicle it is going into. Sometimes we don’t know what kind of driving conditions this vehicle will go through and loads it will pull, so we try to anticipate a little extra protection so we can have a happy customer.

Many times the recipe for the build will include a line pressure boost along with some tuning to help provide better holding power, firmer shifts and quick pressure response. Some will say, when it comes to turning up the pressure, “The higher the pressure, the longer it will live,” and “Too much is never enough.” There are definite benefits to increasing pressure and holding capacity, but there are items connected to line pressure, like the TCC apply circuit, that are designed to have limitations. There are two examples of transmissions of this type. The first is the TCC apply circuit for the 45/545RFE and 65/66/68RFE family. The TCC apply circuit on RFE applications, when in full TCC apply mode, is limited to whatever maximum line pressure is (Figure 1).

On a stock RFE, that max is around 160 psi in the Forward ranges. The interesting thing about this is that the RFE has a TCC regulator valve that is in charge of controlling the amount of TCC apply pressure that gets to the apply side of the clutch, but this valve only functions as a regulator valve during partial apply. Once the TCC goes into full apply, TCC apply pressure will equal line pressure. Modifying the RFE pressure control circuitry does have its benefits, but there also can be some pitfalls related to how high pressure is regulated. Some performance kits will allow line pressure to be in excess of 220 psi. When line pressure gets that high, so does TCC apply pressure. This can cause converter ballooning and/or flex plate damage and eventual damage to the pump assembly and the bellhousing adapter (Figure 2). This increase in apply pressure puts a large amount of force on the crankshaft of the engine. Some have gone to billet torque converter covers to help prevent ballooning, but this does not prevent the additional force from this pressure increase.

The second example of a circuit designed to have limitations is found in the Chrysler RH/RE family. Figure 3 shows a partial oil circuit diagram of the TCC apply valve.

Figure 3 - OE 46-47-48RE TCC Circuit in Full Apply

Notice that this valve is fed line pressure from the manual valve, and when the torque converter clutch is applied, line pressure is fed to the clutch. Compared to RFE units, this family of transmissions has a lower max pressure in Drive near 130 psi when in TCC or in 4th Gear. Performance kits will increase that pressure to 150 psi and higher, which is much lower than the RFE family, but can still cause ballooning.

The TCC apply circuit, on both examples, can benefit from a Sonnax apply limit valve that limits apply pressure near the factory specs. Choose from drop-in Zip Valve^® kits for RFE and RH/RE transmissions and— for RFE units with extreme bore wear — an oversized valve kit that requires reaming. No matter what type of job is on the bench, you can be confident top-quality Sonnax parts will give your build and customers that little extra protection they need. A billet cover converter is definitely a great addition as well.

45RFE, 545RFE, 65RFE, 66RFE, 68RFE
Sonnax valve limits TCC apply pressure to a max of 150 psi, even in chipped and high performance units.

Drop-in TCC Apply Limit Switch Valve Kit 44912-36K Oversized TCC Apply Limit Switch Valve Kit 44912-41K

46RH, 46RE, 47RH, 47RE, 48RE
Sonnax valve limits TCC apply pressure to a max near 130 psi depending on the set point of maximum line pressure.

Drop-in TCC Apply Limit Valve Kit 22771A-44K

Jim Dial is a Sonnax product line manager. He is a member of the Sonnax TASC Force (Technical Automotive Specialties Committee), a group of recognized industry technical specialists, transmission rebuilders and Sonnax Transmission Company technicians.