Subaru transmissions: The seven sisters

Often times I become curious as to the origin of a phrase or a name. This frequently is prompted by the different names I continually see given to vehicles. On one occasion after a day’s work, several of us here at ATSG sat around talking, and I brought this subject up. This provoked a comical story of wit among us using the names of vehicles.

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It was something like a Grand Caravan made a Voyager to Daytona to enjoy a Sebring, then on to Town and Country including 5^th Avenue and Aspen and all the way to the Pacifica.

They had quite a Vision. Grand Cherokee and Comanche argued with the Commander about using a Compass as opposed to doing a Valiant Sundance.

Others just wanted to Cruise using Satellite communication to Charge ahead with Nitro enjoying the Airflow. Some said this was a Cirrus and took the Concorde with pilot LeBaron to Monaco and then Windsor enjoying a Magnum of wine on the way. When the Grand Caravan suffered an Intrepid brake problem with the Caliber, they took the Liberty to go to a Premier show watching a Patriot’s wife be bitten by a Viper, to which he Avenger by a heavy Ram to its head. This was quite coincidental, since the two ended the day romantically enjoying the astronomical sign Aries in the night sky, which is the symbol of the Ram.

It was an amusing time as we continued the story using names from Ford and GM vehicles. But speaking about astronomical signs in the night sky, you might be surprised to learn that Subaru is the Japanese name for the Pleiades star cluster M45, otherwise referred to as "The Seven Sisters." According to tradition, one of these sisters is invisible. This is why Subaru has a blue oval emblem with six stars in it (Figure 1). It also is representative of the companies, which merged together to form Fuji Heavy Industries (FHI). FHI is a Japanese multinational corporation and conglomerate involved in aerospace and ground transportation.

They are the maker of Subaru automobiles, the subject of this article. This will supplement two previous Subaru articles written in 2013, one called “The many Changes to the Subaru 4EAT” and the other “A Second Glance.”

Founded in 1953, Subaru made its presence known here in the United States 15 years later. Interestingly enough, one year after that (1969), we landed on the moon, which I am sure had a better view of the seven sisters. They might have even seen the invisible sister from there.

The car that landed here on U.S. soil was called the Subaru 360. It took on the nickname “Ladybug” due to its similar appearance. (It was also called Ladybird in Europe). It had an air-cooled 2 stroke inline 2 cylinder 356 cc engine mounted transversely in the rear. Sort of like its competitor, the VW Beetle called the Bug, it had a four-speed manual and optional three-speed-based “Autoclutch” transmission. It was called an Autoclutch because it was a manual transmission that eliminated the clutch pedal using and electromagnet to operate the clutch. That makes today’s Sequential Manual Gearboxes with computer controlled slave cylinders not such a new idea. It wasn’t until 1975 that Subaru began using an automatic transmission. It was a 3-speed by JATCO called the 3AT. By 1983, there was an electronic version of this transmission called the 3EAT with a Single-Range 4WD package.

A number of years later they phased out the 3 speed transmission using a 4 speed version, which was available in FWD and Full-Time AWD. It was called the 4EAT transmission. But as the years rolled by, significant changes took place with the design of the transmission. As a result, the original 4EAT is referred to as the 4EAT Version 1 Phase 1. This transmission utilized a band for 2^nd and 4^th gear where shifting was electronically operated (Figure 2). Its powerflow and solenoid operation is that of a Nissan RE4R01A made by JATCO (FIgure 3). Around 1999, Subaru replaced the 2/4 band with a clutch assembly (Figure 4) along with a

completely different valve body and solenoid arrangement (Figure 5). This style of transmission is called the 4EAT Version 1 Phase 2.Part of these changes included AWD control. They use two types of traction control systems: Active Torque Split (ACT-4) and Variable Torque Distribution (VTD). Normally a FWD vehicle, ACT operates on a 60:40 split sending torque to the rear wheels when front traction loss is detected. The VDT utilizes rear traction control more frequently with a 45:55 split and

ypically is found in turbocharger performance model vehicles with the 5EAT transmission mentioned next.The 2004 Forester Turbo was the first to receive a third change with this unit. It is called the 4EAT Version 2 Phase 2, which can be identified quickly by yet another noticeable redesign of the valve body and solenoids. This style transmission found its way into the Forester non-turbo, Impreza turbo and non-turbo as well as the Legacy and Outback vehicles. But 2009 was the last year this transmission was used. The models that did not receive Version 2 Phase 2 received a 5 speed 5EAT transmission with a sport shift package. This transmission

is based on the JATCO JR507E transmission which Nissan uses and calls the RE5R05A transmission.Today, Subaru has committed its entire vehicle line to a CVT transmission called the Subaru Lineartronic CVT. There was a time when Subaru brought a CVT here into the States in its Justy vehicle, which lasted only five years (1989-1994). This transmission utilized a metal powdered clutch between the engine and transmission. This electronically controlled magnetic clutch imitated a fluid coupling torque converter. Brushes running along side the neck would energize the assembly magnetizing the powder to stiffness completing the torque t

ransfer from the engine to the drive pulley.

It was an interesting transmission to say the least. I remember how the engine oil cover would leak; oil would drip down and get the brushes soaked with oil. This prevented the metal powder to become magnetized causing the transmission to not move. Anyway, primarily a FWD transmission, the Lineartronic CVT doesn’t come close to this design. Externally, the design looks similar to the familiar 4EAT transmission (Figure 6). Internally is a different story all together. The only similarity would be the transfer clutch supplying torque to the rear wheels.

One of the common complaints we have had on all three style 4EAT transmission is tight corner braking. This is when the wheels hop and skip across the pavement during low speed turns. This is typically caused by a malfunction in the AWD operation of the transmission.

To break this down, Phase 1 Version 1, the solenoid attached to a 2 valve control body used to apply and release the transfer clutch located in the extension housing (Figure 7). Phase 1 Version 2 this little assembly was located in to the rear of the transmission (Figure 8). In both versions, when the solenoid was turned off it applied the transfer clutch delivering torque to the rear wheels. Energizing the solenoid would release the clutch which is to occur during tight cornering to prevent wheel hop.In the previous “The Many Changes to the Subaru 4EAT” article, it discusses how Subaru provided a test fuse located under the hood called AWD. It is purposely empty. When you

insert a fuse into the holder it will energize the Transfer Clutch Solenoid. If the wheel hop problem is eliminated than an external related issue (ABS/Wheel Speed system) is responsible for the problem. If the problem remains, the problem is internal related to the transfer clutch solenoid, transfer clutch valve body assembly, or the transfer clutch itself.

Phase 2 Version 2 is a completely different story. The entire hydraulic control of the transmission changed affecting computer hardware, software, solenoids, valve body and case passage. Part of these changes eliminated the little transfer clutch valve body assembly and relocated the solenoid to the main valve body (Figure 9). This solenoid can be quickly identifies as it is the only one with a green connector (Figure 10). This is a Normally Vented solenoid which means it needs to be energized to engage the transfer clutch; just the opposite of the two previous designs. This also eliminated the AWD fuse holder in the engine compartment due to this strategy change.

The solenoids with the grey and brown connectors control clutch apply (Figure 11). They are all Normally Applied solenoids which means to turn a clutch off the solenoid needs to be energized. The snout diameters for the grey solenoids are 1.265 inches (TCC, High Clutch and L/R Clutch). The snout diameters for the brown solenoids are 1.365 inches (Low Clutchand 2/4 Clutch). The transfer clutch solenoid with the green

connector has the same snout diameter as the brown connector solenoids (1.365 inches). This means “self-inflicted transmission malfunction” as the brown and green solenoids can be poked into the wrong location. So care needs to be given here when changing solenoids.

Figure 12 is a simple hydraulic schematic showing the operation of this new design transfer clutch solenoid. It receives pilot pressure through a .050-inch orifice into the tip of the solenoid’s snout. When the solenoid is off, the supply pressure is blocked from passing through the solenoid. When the solenoid pulse width modulated by the computer, pilot pressure passes through the solenoid to the transfer clutch control valve. This valve is being held closed by spring tension. Along side the valve is a line pressure supply waiting to be routed to the transfer clutch. When solenoid feed oil enters the face end of the valve opposite the spring end, pressure builds to overcome the spring force stroking the valve. Once the valve moves, line pressure is then directed to the transfer clutch. The way the solenoid strokes the valve, it allows for a controlled apply of the clutch as well as a controlled release of the clutch.

The failure that can occur here is the solenoid mechanically fails where it will apply the transfer clutch without it being energized. This happens to be a common problem with this solenoid. The bigger problem is the solenoid cannot be purchased separately. The entire valve body assembly needs to be purchased which includes all the solenoids listing for a bit over $900. Watch for an in-car repair with a work around for this dilemma which will be in a weekly March 2015 newsletter.

Other causes for the transfer clutch to remain applied besides a mechanically failed solenoid would be a transfer clutch control valve stuck in the applied position. Or the friction and steel plates in the transfer clutch drum have become so overheated they seized together. A couple of reasons for this will be discussed in one of the weekly March 2015 newsletter as well.

Does anyone know what Impreza means? Someone told me it is a Polish word for “show.” Maybe it is referring to the Premier show with the Patriot and his wife. If so, the seven sisters should be attending. My guess is that with their Legacy they might be going Crosstrek through the Forester from the Outback.