Clutch Regulator

Hydraulics Fundamentals: Clutch Regulator Valves

Knowing how these circuits work and the slightly different variations that the manufacturers utilize should pinpoint any valve body-related issues

An understanding of hydraulics is essential for correctly diagnosing and repairing transmission problems. This article is part of a series from Sonnax exploring how valves and hydraulic circuits work and what results when they quit functioning correctly.

Later model transmissions control shift apply and feel by using clutch regulator valves, their actuators, and often, an accompanying valve controlling bias (balance) pressure. The components all take their directions from the transmission control module (TCM), which uses inputs (throttle position, speed sensors, etc.) to assess driver demands and conditions to determine how quickly to set the shift patterns.

Using the GM 6L80 as an example, we can see how these shifts occur. Understanding how the components function, diagnostics of a related shift complaint (harsh or slide shifts, slips and flares, delayed engagements, solenoid codes, burnt clutches) can help pinpoint places in the valve body to look for excess wear, sticking valves, or failed electronics.

figure 1

Examining how a 2-3 shift is made in a 6L80 shows the basics of clutch regulator valve operations and some various designs that are utilized. Figure 1 shows the vehicle in 2nd Gear. 

The variable feed solenoid (VFS) is commanded by the TCM to direct fluid pressure (PCS26CL) to the 2-6 clutch regulator valve. The solenoid will ramp up current flow to increase this pressure based on driver demand. The fluid pressure flows against and through the 2-6 gain valve to stroke the 2-6 clutch regulator valve against the spring force, thus opening the passage for clutch feed pressure (from manual valve) to be directed through the valve to apply the 2-6 clutch.

A portion of this fluid pressure is also directed to the inboard (balance) side of the clutch regulator valve to provide some help to the spring to ensure that the apply pressure is regulated to a specific PSI established by GM. If there is wear in the bore, this pressure can be lower or higher than required for proper clutch apply, resulting in the various shift complaints associated with 2nd Gear.

Because this valve is also used in 6th Gear, similar shift complaints would also occur in 6th Gear – helping you narrow down places to look during
your diagnostics.

Figure 1 also shows a clutch regulator valve design variance: the addition of a gain valve. In 6th Gear, the addition of 456CL pressure is added to the 2-6 gain valve, which reduces the amount of fluid pressure acting to push the 2-6 clutch feed pressure valve to the applied position. This provides better control of the 5-6 shift. Another feature often included in clutch regulator valve circuits is the pressure switch circuits. Fluid pressure is sent through the clutch regulator valve when in the released position to apply a pressure switch. The TCM has confirmation of the valve and presumably clutch position.

Figure 2 shows the vehicle in 3rd Gear – so the 2-6 clutch is released, and the 35R clutch is applied. 

figure 2

Likewise, the related VFS solenoids PCS4 and PCS 2 are de-energized and energized, respectively. The 35R clutch regulator valve design has a slightly different design variation that is common. As the PCS35R CL pressure strokes the valve inboard, this opens the passage for 35R feed pressure to flow through the valve and apply the 35R clutch. A portion of this oil pressure is also directed to the 35R clutch boost valve, which is also being actuated by the #2 pressure control solenoid. This boost valve directs limited 35R clutch feedback pressure to the balance side of the clutch regulator valve, which helps control the ramp-up of the 35R clutch. So wear at these clutch boost valves can directly impact shift feel related to that particular clutch circuit. 

Figure 2 also shows another typical circuit on later model transmissions associated with clutch regulator valves: the use of exhaust backfill. As an apply component is released, instead of simply dumping all of the apply pressure to exhaust, a portion of the fluid will remain in the circuit via the exhaust pressure backfill circuit.

This pre-fills the circuit, allowing for a quicker apply of the component when commanded. Because fluid left in the apply circuit could create an inadvertent or partial apply of the clutch, a countering pressure from the compensator feed circuit is directed to the opposite side of the clutch apply piston to prevent unwanted or centrifugal apply of the clutch.

Knowing how these circuits work and the slightly different variations that the manufacturers utilize should pinpoint any valve body-related issues responsible for various shift complaints and clutch failures.

Maura Stafford is a Sonnax product line manager for transmission components and remanufactured valve bodies. She 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.

You May Also Like

Sherlock Holmes Approach to an AB60 No-Move Situation

The effectiveness in diagnosing automatic transmission malfunctions is an art form. Although there are similarities among the wide varieties of transmissions on the road, each transmission has its own peculiarities. Aside from having mechanical, hydraulic, and electrical hardware systems to contend with, software/programming issues and various vehicle platforms make diagnostics much more difficult.  Using scopes provides

ab60

The effectiveness in diagnosing automatic transmission malfunctions is an art form. Although there are similarities among the wide varieties of transmissions on the road, each transmission has its own peculiarities. Aside from having mechanical, hydraulic, and electrical hardware systems to contend with, software/programming issues and various vehicle platforms make diagnostics much more difficult. 

GM 6T40 Pump Identification Guide

The 6T40 was introduced in 2008 for General Motors front-wheel-drive cars in the Chevrolet Malibu and has gone through several changes throughout its three generations, specifically in the pump area. The 6T40 is closely related to the more lightweight 6T30 and the heavier duty 6T45 and 6T50. Generation one started phasing out during the 2012

Seeing the Forest AND the Trees

They say that the proverbial phrase “I couldn’t see the forest for the trees” means that a person or organization cannot see the big picture because it focuses too much on the details. Related Articles – 4L60E Harsh 1-2 Shift – TASC Force Tips: Diagnosing 8L45 & 8L90 Shift Complaints – TASC Force Tips: Hydraulics

The Manifold Pipeway

The Honda six-speed transmission has been on the bench of many specialty shops for one reason or another (figure 1). But, for those of you who have yet to lay your hands on one, mounted on the upper side of the unit is one of the largest, if not the largest solenoid and pressure switch

8L90 Vacuum Testing

Below are the diagrams for vacuum testing GM 8L90 transmissions. Note: OE valves are shown in rest position and should be tested in rest position unless otherwise indicated. Test locations are pointed to with an arrow. Springs are not shown for visual clarity. A low vacuum reading indicates wear. For specific vacuum test information, refer

Other Posts

Kitting keeps us profitable: Aftermarket kit suppliers listing 2024

The kitting of transmission parts has made profitable shop operation possible. When a kit with 100 parts is necessary, a distributor has already assembled all the important components into the kit and it is typically sitting on the shelf ready to be delivered. Kitting saves time and effort for both the shop and the supplying

Watch out for high pressure in GM 8L45, 8L90 valve bodies

Hey now! Oh boy, do I have a fun failure to share with you and warn you about today! Related Articles – Chrysler RH/RE late shifts and high pressure – Ford 6R80 shift solenoid ‘E’ resistance change: How to tell the difference – Allison 1000 geartrain bind-up Have you encountered a crack in the worm

Shift of the shaft: Diagnosing Chrysler 48RE manual shaft issues

The TorqueFlite transmission has been around since mid-to-late 1950s. There have been many changes surrounding the manual shaft and rooster comb through the years. This transmission shaft controls the position of the manual valve that directs oil for the gear ranges, but it also is used for a Reverse light control as well as Park/Neutral

Diagnosing Ford 10R60, 10R80 and 10R140 series speed sensor issues

Ford 10-speed 10R series transmissions utilize four two-wire, Hall-effect sensors — TSS, ISSA, ISSB and OSS — for providing speed signals to PCM or TCM. They are supplied nine volts by a PCM or TCM and assist in the control of clutch apply/release timing that is used in determining shift quality, including TCC. Related Articles