Tales From the Bench - October/November - 2015

Subaru CVT Gen 2 Valve Body

Information is the key to success in this industry. But lately, manufacturers have begun to spend a lot more effort building barriers between you and the information you need. At ATRA, our job is to break down those barriers and provide you with the best possible information available.

Information on the Subaru Generation 2 CVT valve body is hard to find because it isn’t published. Subaru doesn’t make it available because they sell the valve body; not the individual components. If you need a solenoid or find a worn-out valve, there’s no fix available from the manufacturer besides replacing the entire valve body.

But we’re transmission technicians: We find ways to overcome these obstacles. And that’s why we’re publishing this information; to make it easier for you to find the root cause of the failure when rebuilding Subaru CVTs.

It took a while, but we were able to trace the valve body passages and work out the function of each valve. In this article, we’re going to examine the functions of the valves and solenoids, and provide you with the spring sizes to help you rebuild these units successfully.

Removing the Valve Body

Removing this valve body with the transmission still the car doesn’t look easy, because the valve body is on the top of the transmission. Subaru has a special cloth sheet for this procedure, to cover the engine and keep dirt out of the transmission.

You’ll also need to take the throttle body off to provide enough clearance to remove the valve body. It isn’t easy, but it’s possible if necessary.

The valve body is under a sound shield and an aluminum cover. Once you’ve removed the sound shield and the twelve, 10mm-headed bolts on the cover, pull the cover up and unplug the valve body main solenoid connector (figure 1).

Next, remove the nine, 10mm-headed valve body-to-case bolts (figure 2). Make sure you don’t remove all the bolts: If you remove the other bolts, the small parts from the valve body may fall into transmission.

With the valve body removed, look for two O-rings in the case (figure 3); they may be stuck on the bottom of the valve body.

Once you have the valve body on the bench, flip it over to reveal most of the solenoids on the lower section of the valve body.

Solenoid Info and Wire Colors

The Gen 2 CVT has six solenoids mounted to the valve body to control transmission operation (figure 4):

The Secondary Line Pressure Control solenoid is an unusual solenoid; it has the pressure regulator valve in its snout. The solenoid operates at 2000 Hz and it controls an orifice with a needle and seat. The orifice controls the position of the pressure regulator, which controls line pressure.

The secondary line pressure control solenoid should measure around 5-7 ohms resistance. It has a single red control wire so the solenoid is grounded through the valve body.

The Forward/Reverse Linear solenoid controls the forward/reverse regulating valve. The manual valve directs the regulated oil to the forward or reverse clutch, depending on its position.

The forward/reverse solenoid is pulse width modulated. It should measure around 4-6 ohms resistance. The wires to the solenoid are gray and white.

The Lockup Duty solenoid controls the position of the lockup slip control valve. When the solenoid is off, fluid pressure applies to the release side of the torque converter, releasing the converter clutch. As solenoid duty cycle increases, it gradually moves the lockup slip control valve to close the apply circuit, which opens the release circuit. This bleeds the pressure from the release side of the converter clutch, allowing it to apply.

The lockup duty solenoid should measure around 10.0-13.5 ohms resistance. The solenoid wires are light green and gray. This is a normally closed solenoid.

The Primary Up and Primary Down solenoids work together to control the transmission gear ratios. Line pressure enters the primary up shift valve and becomes primary pressure, controlled by the primary up solenoid.

As pressure enters the primary pulley it squeezes the pulley together. This pushes the belt out toward the edge of the pulley, effectively making its circumference larger and changing the ratio. At the same time the secondary pulley opens, making its effective circumference smaller.

At steady speeds or while maintaining the same ratio, the primary up and primary down solenoid signals are balanced to keep the ratio steady.

When lowering the ratio, the primary down solenoid moves the primary down shift valve, which lowers the pressure in the primary pulley. This opens the pulley, allowing the belt to ride lower, which effectively reduces its size. At the same time the secondary pulley closes, effectively increasing its size.

Primary up and down solenoids both have around 10.0-13.5 ohms resistance. The primary up solenoid wires are black and purple. The primary down solenoid wires are gray and blue. Both solenoids are normally closed.

The All Wheel Drive solenoid controls the transfer clutch slip control valve, which supplies oil pressure to the transfer clutch. This is a normally-closed, duty cycle controlled solenoid; as the duty cycle rises, the pressure increases to the transfer clutch.

The solenoid should measure 2.0-4.5 ohms resistance. The solenoid uses black and orange wires.

Valves and Small Parts

After you remove all the bolts on the lower side of the valve body, flip it over and remove the bolts from the upper section. Remove the upper section of the valve body and inspect the valves and bores (figure 5).

The upper valve body contains these valves:

  1. primary down
  2. primary up
  3. forward/reverse regulator
  4. transfer case clutch slip control
  5. torque converter pressure
  6. failsafe
    Look for all the small filters and relief valves in the middle section of the valve body. Be careful removing the separator plate and note their locations (figure 6).
    The middle section contains the forward and reverse solenoid, along with all these valves:
  7. pilot
  8. forward and reverse limit
  9. primary relief
  10. lube/drainback
  11. torque converter clutch control/torque converter clutch regulator

The lower section houses the secondary line pressure solenoid and the lube check valve #12 (figure 7).

As you can see, this valve body isn’t overly complex; refer to figure 8 to identify the valves and spring sizes.

Hopefully this article has broken the barrier between you and the Subaru Generation 2 valve body. With this new information in hand, you should have no problem identifying and repairing these valve bodies and solenoids.

Special thanks to Perfection Plus Transmission Parts, in Portland, Oregon, for the use of this core.