Unlocking Some 55-50 Valve-Body Mysteries - Transmission Digest

Unlocking Some 55-50 Valve-Body Mysteries

Let’s start with identifying the AW 55-50 valve body and the differences that matter when you’re choosing a replacement valve body. There are four castings, which can be identified by either a letter cast into the valve body just to the right of the S4 solenoid or a blank spot.
Unlocking Some 55-50 Valve-Body Mysteries

Body of Evidence

Subject: Different design levels of valve body
Unit: AW 55-50
Vehicle Applications: GM, Nissan, Saab, Saturn, Volvo
Essential Reading: Rebuilder, Diagnostician, R & R 
Author: Jeff Parlee

Body of Evidence

  • Subject: Different design levels of valve body
  • Unit: AW 55-50
  • Vehicle Applications: GM, Nissan, Saab, Saturn, Volvo
  • Essential Reading: Rebuilder, Diagnostician, R & R
  • Author: Jeff Parlee

Let’s start with identifying the AW 55-50 valve body and the differences that matter when you’re choosing a replacement valve body. There are four castings, which can be identified by either a letter cast into the valve body just to the right of the S4 solenoid or a blank spot.

The blank-spot (no letter) and A castings are considered early because the electrical connectors on the SLS and SLT solenoids face up (figures 1 & 2).

The B- and C-casting valve bodies are considered late because the SLS and SLT solenoids have the electrical connectors facing down (figures 3 & 4). The early vehicles (2000 to sometime in 2002-2003) had an internal wiring harness that was just long enough to connect to the SLS and SLT solenoids with the electrical connectors facing up.

When the B valve body was introduced with the SLS and SLT electrical connectors facing down, the internal harness was made longer to accommodate the change.

The next wrinkle in our identification is which S2 solenoid the valve body has. Nissan and Volvo use a normally closed S2 solenoid that has a flat top with four ribs radiating from the center hole on top to the outside corners (figures 1 and 4). GM, Saab and Saturn use a normally open S2 solenoid that has a domed top (figures 2 and 3).

Now we can look at an AW55-50 valve body and tell whether it is early or late and whether it is a GM style or a Nissan/Volvo style. That was all you needed to know until 2005. Beginning in the 2005 model year, Nissan, GM and some Volvos changed the way that they fire the solenoids and added a spring to the inboard side of the B5 control valve. If a valve body without the B5 spring is installed on a 2005 or newer vehicle, you will get a nasty 3-2 coast-down clunk. If you install a valve body with a B5 spring into a 2004 or older vehicle you will get a 2-3 flare that will not adapt out.

It is important that you verify the model year of the vehicle by looking at the 10th digit of the vehicle identification number (VIN). A 4 in the 10th position would mean 2004, a 5 would mean 2005 and so on. If the vehicle is a 2005 or later, most will have the B5 control-valve spring (Figure 5). An exception to the rule is that some early Saturns have a B5 control-valve spring. It is best to order a replacement valve body by identifying the letter code and whether it has a B5 control-valve spring because of various updates by the manufacturers over the years.

Let’s talk about the linear solenoids and the correct way to install the SLT/SLS-solenoid bracket. There are three design levels of the SLT and SLS solenoids. The first design is shorter than the later designs and requires the early SLT/SLS hold-down bracket (Figure 1). You can identify the early, short solenoids by the round hole in the slot where the bracket goes and the electrical connector that faces up (Figure 6). The first-design SLT/SLS solenoids are used on the valve-body casting with no letter.

The second-design solenoids are longer and the electrical connector faces up. The second-design SLT/SLS solenoids are used on the A-casting valve bodies (Figure 2).

The third-design solenoids are the same length as the second-design, but the electrical connector faces down. The third-design SLT/SLS solenoids are used on the B- and C-casting valve bodies. Both the second- and third-design SLT/SLS solenoids require the late hold-down bracket with the backward L at the bottom (figures 3 and 4).

Always install the hold-down brackets with the narrow end of the bracket facing up.

A good way to verify that the SLT/SLS hold-down bracket is installed correctly is to look into the exhaust slot for each solenoid to see whether the slot on the solenoid is aligned with the exhaust slot.

If the solenoid is blocking the exhaust slot, the bracket is on upside down or the wrong bracket is being used (Figure 7). If the exhaust slots are blocked, line pressure will go to maximum and the engagements and shifts will be harsh.

AW 55-50 valve-body-identification quick reference:

  • Determine early or late valve body by using the letter code to the right of the S4 solenoid: No letter or A = early valve body, B or C = late valve body.
  • Determine Volvo/Nissan or GM/Saab/Saturn valve body by the shape of the S2 solenoid.
  • Determine 2005-up on B & C valve bodies by checking for a B5 control-valve spring (Figure 5).
  • When installing the SLS and SLT solenoids, always install the hold-down bracket with the narrow side up (figures 2, 3, 4 and 7).
  • Use the early SLS/SLT hold-down bracket with only the first-design solenoids that have the round hole in the snout (figures 1 and 6).

With this information you should be able to identify any AW 55-50 valve body.

Jeff Parlee is director of product support at ValveBody Xpress.

You May Also Like

The Subaru mystery burn

The Subaru TR580 transmission is known for having torque converter clutch solenoid failures. An example of this can be seen in Figures 1 (above) and 2 (below). The solenoid resistance should be between 10 to 13.5 ohms. The resistance right at the solenoid itself on the valve body is close to 38 ohms. And as

Tech-Speak-May-Figure-1-1400

The Subaru TR580 transmission is known for having torque converter clutch solenoid failures. An example of this can be seen in Figures 1 (above) and 2 (below).

The solenoid resistance should be between 10 to 13.5 ohms. The resistance right at the solenoid itself on the valve body is close to 38 ohms. And as most techs know, this solenoid is not available separately from the dealer, nor are any of the other solenoids available separately for purchase. The entire valve body has to be purchased for a single solenoid repair. Companies like Rostra and Dorman make this TCC solenoid available separately, giving the shop an option for an affordable fix. 

Shift Pointers: Where’s that fluid leak coming from?

A 2016 Honda CRV 2.4L (Figure 1), using a BLJA CVT 4WD transmission (Figure 2) comes in to a shop with a customer complaint of a leak. Related Articles – The powertrain aftermarket: Growing and global – Multitasking: Sorting out multiple issues with the same vehicle – Chrysler RH/RE late shifts and high pressure Before

Multitasking: Sorting out multiple issues with the same vehicle

While it’s common for a customer to bring us a vehicle with a single, specific complaint, we often find more than one problem when getting into the diagnosis of their original concern. The owner only knows one thing; they want the vehicle to run and operate properly. It’s our responsibility to identify and execute a

Chrysler RH/RE late shifts and high pressure

You may find that these transmissions have a late 1-2 and 2-3 shifts along with high TV/line pressure.

Ford 6R80 shift solenoid ‘E’ resistance change: How to tell the difference

The lower resistance and higher resistance solenoids are not interchangeable.

Other Posts
Alto introduces Nissan high-performance friction, steel module

Alto has introduced a new high-performance friction and steel module for Nissan RE7R01A and JR710E transmissions. Related Articles – PRT adds 28 new strut assemblies – Milton Industries introduces new AirStrike air hammer – K-Tool offers Ultimate Torq socket sets  According to the company, it features G3 frictions and Kolene steels, and contains C1, C2

Alto-Nissan-Friction-1400
Autel tablets approved for Nissan Central Gateway access

Autel has announced that its tablets have been approved for Nissan Central Gateway (CGW) access via AutoAuth, the aftermarket tool OE-authentication service, enabling registered users to access secured systems and perform complete diagnostics on certain late-model Nissans. Related Articles – Torque converter supplier listing 2024 – Sonnax highlights 1350 Series three-bolt adapter flange yoke kit

Autel-Nissan-auto-auth
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 – A part for every need: Hard parts supplier listing 2024 – Ford 8F24 mechanical diode failure – Back with force: ATSG is back in full swing to educate the transmission industry Have you