The valve body and its solenoids serve as the heart and brain of the automatic transmission. Why are they so important and unfortunately SO costly to repair or replace? Since the invention of the automatic transmission in 1921 and the first hydraulic transmission in 1932, manufacturers have worked to improve driver comfort, vehicle performance, and gas mileage. The latter, fuel economy, has become increasingly important in recent years due to environmental concerns. As a result, automatic transmissions have undergone great changes and have become incredibly complex systems. While older transmissions had 2, 3 or 4 speeds or “gears,” modern automatics have seen 10 speeds or more along with multiple reverse gears. Modern electronic systems monitor performance and control the transmission while driving. The valve body and solenoids play a central role in the operations of these modern transmissions, which we will look at in greater detail.
The valve body acts as the control center of the automatic transmission. Usually made of aluminum (Fun Fact: valve bodies in much older vehicles were cast iron allowing for greater durability yet the weight hindered fuel economy), it contains a maze of channels and passages that direct the transmission fluid through valves to control the various clutches, bands and drums that change gears.
Vehicles have a number of sensors that are monitoring vehicle speed, engine load and throttle position and send this information to an onboard computer, which in turn communicates with the valve body in order to shift up and down between gears. When a shift is needed, valves open and close to direct transmission fluid to the appropriate area to make the gear change occur. Transmission fluid, unlike motor oil, is more than just a lubricating fluid; it’s a hydraulic fluid. The transmission fluid flowing through the valve body is under tremendous pressure, which in turn generates heat. As the soft parts in the transmission break down, they leave small particles in the fluid as contaminants, which becomes abrasive.
This combination of pressure, heat, water intrusion and abrasion has a negative impact on the valve body over time. The valves will wear down, the channels can be abraded and become oversized, and the whole valve body unit can become warped. Signs of a bad valve body can be fluid leaks, slipping during gear changes, or even failure to go into gear.
Transmission Specifics:
Nissan has sold millions of dollars of RE5 valve bodies because of a faulty radiator. These units are found in Nissan Xterra, Nissan Pathfinder and Nissan Frontier models. A poor design causes a breach in the radiator causing coolant (glycol or radiator fluid) to sneak into the transmission coolers lines and ultimately cause water contamination in the transmission. The biggest downside to this scenario that motivated a national class action suit against Nissan is the rust that forms on the valve body that prevents the proper operations of valves. Once contaminated, there’s no turning back unless the valve body is replaced, among other items required in a quality transmission rebuild.
A solenoid is basically an electro-hydraulic switch that controls the valves in the valve body. Information from a vehicle’s computer opens and closes these switches in order to control the flow of transmission fluid and therefore the function of the transmission. Solenoids control torque converter lockup, internal transmission pressure, and shifting. As modern transmissions have become more complex, especially with electronic complexity, the number of solenoids has gone up as well. Older 4 speed transmissions may have only 2 or 3 solenoids, while some new 8 and 10 speed transmissions may have 13 or more!
Additionally, solenoids themselves have become more sophisticated. Older designs are simply binary in that they are either “on” or “off” – it’s a switch. Newer designs are often “pulse width modulated” or “variable force” solenoids. These allow the computer to adjust timing and volume of the valve opening and closing to maximize fuel efficiency and performance. Depending on manufacturer and design, these solenoids can be inside of the transmission or mounted on the outside of the housing. All in all, transmissions have become less and less dependent on mechanical and hydraulic systems and more dependent on computers and electronic controls.
Transmission specifics: Commonly found in models such as the Silverado, Suburban, Tahoe or Denali, the GM 4L60E was originally designed with a simple binary TCC (torque converter clutch) solenoid. However, the abrupt “on-off” function caused a number of premature failures in these units, leading GM to incorporate a “pulse width modulated” solenoid. This allowed a gradual lockup of the torque converter and reduced these premature failures.
The downside is that electronic components can and will fail. A solenoid can stick open or stick closed, or simply become erratic and inconsistent. When this happens, transmission problems can show up rapidly. Too much internal pressure can cause hard shifts, while too little pressure will rob the transmission of fluid causing overheating that will destroy clutch packs. A bad solenoid can cause delays in shifting, or even shifting into the wrong gear or shifting up and down unpredictably. A bad solenoid often signals an error to the computer and a “check engine” light will come on.
Transmission Specifics:
The Dodge 42RE/47RE/48RE transmission series have a history of problems with the transducer and pressure solenoids. When a solenoid is charged, it becomes magnetic. The solenoids in these Dodge transmissions are notorious for picking up metallic particles quickly and behaving erratically, causing delayed and or missed shifts. Identifying the problem and addressing it quickly can save a lot of headaches!
If your transmission’s valve body has become worn or damaged, this will usually require a proper rebuild of the transmission to repair. Occasionally this will involve simply rebuilding or replacing the valve body, but this is usually a shortcut that will lead to more problems. A bad valve body is usually a sign that there is more damage inside of the transmission, and a transmission expert needs to fully disassemble and inspect the entire transmission to ensure that everything is up to the manufacturer’s specifications. A transmission is filled with wearable components such as gaskets, seals and clutches that will deteriorate over time. Why spend money on a valve body repair when the “soft parts” have significant wear and can give out anytime?
With a bad solenoid, repairs can often be more straightforward, especially if the vehicle mileage is low and the application is not heavy duty. Assuming a solenoid failure is caught early enough, before too much damage has been done, a replacement of the bad switch can often resolve the transmission malfunction. That full rebuild for several thousand dollars that you feared might be taken care of for a few hundred dollars instead! However, it is best to have a full diagnosis performed by a transmission shop to determine the best course of action to get your vehicle up and running again. This is where an honest local transmission shop is important to program into your speed dial!
Transmission Specifics:
Dodge-Chrysler vehicles, especially Ram trucks or Jeeps, carry a 545RFE transmission that integrates its solenoids into a single block of numerous solenoids. Erratic shifting on these units is a typical problem and often can be tracked to a malfunctioning solenoid within the block. Unfortunately, these situations are not limited to high mileage situations. In low mileage situations, the solenoid block alone can be replaced saving a customer thousands of dollars required for a full transmission rebuild.
The Advanced Transmission Center team consists of technicians who have decades of experience diagnosing, rebuilding and repairing automatic transmissions in domestic and import vehicles. We have the ability to test and diagnose problems with your valve body or your transmission solenoids and use only quality parts in our repairs.
If you are having problems with your valve body, solenoids, or any transmission related issue, contact Advanced Transmission Center at either of our shop locations and we’d be happy to help! Unlike dealerships or many independent repair shops, we are transmission specialists trained to fix issues related to a vehicle drive-train. You can reach out to either location that is most convenient for you.
Related links:Industrial valves are made up of many different components that allow them to regulate flow. The main parts of a valve designs can be divided into the body, trim, actuators, and ancillary accessories. This table provides a brief overview of the primary valve components and their functions:
Valve PartDescriptionValve BodyThe main pressure boundary of a valve that contains the flow. Usually made of cast or forged metal.BonnetThe cover that allows access to the valve internals for assembly and maintenance. Bolted, threaded, or welded to the body.TrimThe internal moving components that modulate the flow, such as the disc, ball, plug, or gate.SeatThe stationary surface against which the movable trim seals off flow. Precision machined based on trim type.StemThe component that connects the actuator to the trim, allowing motion to control flow.PackingCompressible rings that seal around the valve stem to prevent leakage. Requires periodic replacement.GasketUsed to seal non-moving parts, like between the bonnet and body. Provides high integrity seal.ActuatorProvides the force to open and close the valve’s internal parts. Can be manual, pneumatic, hydraulic or electric.PositionerControls the actuator so the valve moves to the precise flow control position demanded.Limit SwitchesFeedback devices to indicate open and closed position for monitoring.Gear OperatorsGears that allow manual handwheels or actuators to produce high valve torques with lower input effort.The valve body, also called the shell, housing, or casing, is the primary pressure boundary of a valve. It serves as the framework that holds together all the other valve parts in proper alignment. Valve bodies are designed to withstand pipeline pressure, temperature, and mechanical stresses. The inlet and outlet of the valve body connect to the piping system. There are various body styles and configurations, with the most common being globular, straight-through, angle, and Y-pattern. The body shape depends on the valve’s intended flow control function. Gate, globe, check, ball, plug, and butterfly valves all have distinctive body designs tailored to their unique flow control application. Valve bodies are cast or fabricated from materials like carbon steel, stainless steel, cast iron, alloy steel, and forged steel. The material is chosen based on the process fluid composition, pressure, and temperature. Many valve bodies have flanged ends to enable connection to piping. Others may have threaded, socket weld, or butt weld ends. No matter the style, the valve body must be strong enough to withstand the system pressure when the valve is in the closed position. It must also be rigid and resistant to warping or cracking that could cause leaks.
There are various options when selecting valve body materials based on the service conditions. Carbon steel is suitable for water, oil, and gas service. Stainless steel handles more corrosive fluids like acids or wet chlorine gas. For extremely high temperatures, alloy steel and cast iron are better choices. Cryogenic valves for frigid liquids like LNG use stainless steel or forged carbon steel bodies. The body material also affects maintenance requirements. For example, carbon steel is prone to rusting or corrosion over time and may need frequent repairs. Stainless steel and alloy steel have higher corrosion resistance, extending the service life. In highly abrasive applications, a hardened valve body is required to resist wearing. No single material is ideal for all applications. Consider fluid composition, pressure, temperature ranges, and desired valve life when choosing a body material. Partnering with an experienced valve supplier is key to getting the right metal for reliable service.
The valve bonnet is the cover on the upstream side that completes the pressure shell of a valve body. It also provides the means for assembling the internal valve parts and accessing them for maintenance. There are three main bonnet configurations: screw, bolted, and welded. A screw bonnet has threads that engage with the body and provides a compact means of assembly. It is easy to open and close for routine inspection and repairs. Bolted bonnets have a separate flanged head that connects to the body using long bolts. This allows very large valves to be assembled in sections. Bolted bonnets are common on gate, globe, and check valves over NPS 2. Welded bonnets have the cover permanently welded to the body. No threads or bolts are used, creating a tight seal. However, this does not allow accessing internal parts without cutting. Welded bonnets are preferred for high pressure and temperature systems where bolts or threads could leak. They also cost less than bolted styles. When selecting a bonnet type, consider the maintenance needs, potential leakage risks, valve size, and expense. The bonnet must withstand system pressure and temperature fluctuations. Leak-proof, easy disassembly and assembly is ideal for most applications.
Valve trim refers to the internal moving parts that modulate flow such as balls, plugs, discs, and gates. The trim comes in contact with the process fluid, so its material must handle the chemical, temperature, and abrasive characteristics. Hardened trim materials include tungsten carbide, Stellite alloys, titanium, Inconel high-nickel alloys, and 440C stainless steel. These withstand highly erosive or corrosive substances. Softer trim materials like bronze, aluminum, Monel, and 304 stainless suit less destructive fluids. The trim material really depends on the fluid composition. For example, a high nickel alloy is better for hydrofluoric acid compared to regular stainless steel. Cryogenic valves need trim that handles freezing temperate without becoming brittle. Abrasive slurries require durable trim that resists wearing. Partnering with an experienced supplier is key to getting the right trim materials for your specific process conditions. This ensures long service life and minimal erosion damage.
Valves use sealing systems to prevent fluid leakage between the stationary body and moving parts. Packing and gaskets are the two main sealing methods. Valve packing consists of rings made of soft, deformable material like graphite, PTFE, or flexible graphite. The rings fit around the valve stem and compress when the bonnet or gland follower tightens. The soft packing deforms to create a tight seal. Packing can leak over time and must be periodically tightened or replaced. It allows some controlled leakage for lubrication. Gaskets provide a more permanent seal between two mating surfaces. Common types are spiral-wound metal, ring joint, kammprofile, and flat paper or plastic. Gaskets require more precision machining for leak-proof performance. Packing handles frequent disassembly better since gaskets can be damaged during maintenance. For fugitive emissions control, metal gaskets are preferred over packing. However, packing enables easy stem movement and regular adjustment. Consider maintenance needs, allowable leakage, and emission regulations when choosing packing or gasket seals.
Gate valves use linear motion gates to start and stop flow. The gate and valve disk can be flexible or solid. Flexible wedge gates have a solid top edge but flexible sides made of metal bellows or laminated sheets. This allows the gate to match the bore when seating, creating a tight seal even on worn valve seats. However, bellows can burst or laminations separate after frequent flexing. Solid wedge gates are a one-piece solid gate that cannot flex. These provide a sturdier gate but require precision machining for effective sealing without leakage. Solid wedges are better for high pressure or frequent operation. Flexible gates suit low pressure modulating control where tight shutoff is needed. Gates must be resistant to cutting, scoring, and deformation from fluids. Flexible gates suit liquids and clean gases. Solid gates work for steam, gases with solids, and contaminated fluids where a bellows could rupture. Consider shutoff requirements, pressure, media properties, and desired service life when choosing between flexible and solid gate designs.
The valve stem translates motion from the actuator to the flow controlling element inside the valve. It may have a rising or non-rising design. Non-rising stems remain vertical as the valve operates. The stem is threaded into the gate, plug, or ball and turns it without lifting. Rising stems lift up and down with valve motion while remaining attached to the flow control element. Rising stems indicate valve position and can automate control via positioners. Non-rising stems require separate shaft position indicators. Rising stems are common on gate and globe valves. Non-rising stems suit ball and plug valves where turning motion is required. Non-rising stems work well for buried valves or corrosive fluids where rising stems could get damaged or cause binding. The stem must align with the actuator and match its torque output. Consider maintenance needs, automation requirements, and environments when selecting between rising and non-rising stem designs.
The backseat is a wearing surface on the valve stem that contacts the bonnet when the valve is fully open. It serves several purposes. First, it provides an additional seal between the stem and bonnet. This isolates the bonnet from system pressure when doing maintenance. It also gives the valve a bidirectional shutoff ability – seal both upstream and downstream. Backseats also enable packing adjustment and replacement while the valve is pressurized. Finally, backseats can act as a stopping point when fully open, preventing damage to seating surfaces. Backseats are common on gate, globe, and check valves. They should have enough surface area to prevent excessive wear. Stainless steel, brass, or carbon graphite materials work well. Consider whether backseats would facilitate safer maintenance when selecting valves. But they aren’t recommended for infrequently operated emergency shutoff valves.
Actuators provide the force to open, close, and position the valve. Common types are linear actuators, quarter-turn actuators, and multi-turn actuators. Linear actuators apply thrust along the stem’s axis to drive gates, globes, or diaphragms up and down. These are often pneumatic cylinders or hydraulic pistons. Quarter-turn actuators rotate 90 degrees to open/close ball, plug, and butterfly valves. Manual lever arms, electric motors, or pneumatic cylinders are common quarter-turn actuators. Multi-turn actuators use gearing to allow for multiple 360 degree rotations. These automate precise positioning of globe and gate control valves. Another benefit of gearing is the high output torque from a small electric motor or manual handwheel. When selecting valve actuators, consider torque requirements, speed, automation needs, space constraints, and hazardous area rating. The actuator output must match the torque demands of the valve, especially for 100% shutoff.
Valves contain many components, and material choices depend on the application. For steam systems, metal seats, bonnets, and steam-rated packing suit the high temperature and avoid oxidation. In cryogenic applications, the body, trim, and seals require materials that stay ductile at freezing temperatures like stainless steel. Highly corrosive fluids need stainless steel or alloy bodies and trim along with corrosion inhibiting sealant on gaskets. For throttling control valves, components supporting smooth stem movement and flow characterization are essential. This includes characterized trims, modified trim geometry, low-friction packings, and high resolution actuators. The principles are the same, but components must be tailored to safely handle the operating conditions. Partnering with an experienced supplier ensures that all valve parts are suited to the service.
Properly selecting valve components requires careful consideration of the service conditions, performance requirements, and desired valve type. Here are some important considerations when choosing valve parts:
For welding end valves, ensure the valve-body ends and weld joint design suit the piping system and materials. Flow mediums that require tight shutoff may need metal-seated ball valves with properly matched stem threads, outside screw and yokes that prevent side loading. High pressure applications need sturdy valve bonnets, thick stem packing in the stuffing box, and sturdy yoke bushings.
Relief valves require precise trim parts and trim designs to provide accurate pressure control. Ball valves used for throttling duties require characterized ball and seats to control flow. The rotational motion of ball and plug valves depends on quality bearings and seals internal elements.
Control valves rely on valves bonnets, gaskets, stem packings and other parts to prevent leakage and enable smooth actuation. The top of the yoke and downstream side covers of a swing-check valve see the most wear, so durable materials are vital.
Choosing control valves also means matching the actuator style and output to provide the right type of motion – rotary for 90 degree ball valves or linear for globe designs. This ensures proper valve positioning and tight shutoff when closed.
No matter the valve type, considering spacing, installation, and maintenance requirements will guide the selection of compact wafer, lugged, or flanged designs. Partnering with experienced suppliers and following PMI standards ensures the parts selected provide long service life.
Understanding how the various internal parts of valves work together is critical for engineers, maintenance staff, and plant operators. The body, bonnet, trim, stem, seals, and actuators all play a role in controlling fluid flow safely and reliably. Component selections must be based on service conditions and performance goals. With the right knowledge of component functions and material differences, industrial valves can be kept in prime operating condition for their essential role in managing fluids.
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