A transmission solenoid is an electro-hydraulic valve that controls fluid flow into and throughout an automatic transmission

Automatic transmission

An automatic transmission is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually...

. Solenoids can be normally open or normally closed. They operate via a voltage or current supplied via the transmission computer or controller. Transmission

Transmission (mechanics)

A machine consists of a power source and a power transmission system, which provides controlled application of the power. Merriam-Webster defines transmission as: an assembly of parts including the speed-changing gears and the propeller shaft by which the power is transmitted from an engine to a...

 solenoids are usually installed in a transmission valve body, Transmission Control Unit

Transmission Control Unit

A transmission control unit or TCU is a device that controls modern electronic automatic transmissions. A TCU generally uses sensors from the vehicle as well as data provided by the Engine Control Unit to calculate how and when to change gears in the vehicle for optimum performance, fuel economy...

, or transmission control module.

Types

• Variable Force Solenoid
  Variable force solenoid
  A variable force solenoid is an electro-hydraulic device that controls pressure proportionally or inversely proportionally to a signal obtained from the on-board controller of a powertrain. A low-flow VFS is used as a signal level devices for transmission line pressure control or application of...
  
   (VFS)
• On-Off Solenoid
• Pulse-Width Modulated
  Pulse-width modulation
  Pulse-width modulation , or pulse-duration modulation , is a commonly used technique for controlling power to inertial electrical devices, made practical by modern electronic power switches....
  
   Solenoid (PWM
  Pulse-width modulation
  Pulse-width modulation , or pulse-duration modulation , is a commonly used technique for controlling power to inertial electrical devices, made practical by modern electronic power switches....
  
  )
• Low Leak Variable Bleed Solenoid

Manufacturers

• BorgWarner
  BorgWarner
  BorgWarner Inc. is a United States-based worldwide automotive industry components and parts supplier. It is primarily known for its powertrain products, which include manual and automatic transmissions and transmission components, , turbochargers, engine valve timing system...
  
   Official Website
• Eaton
  Eaton Corporation
  Eaton Corporation is a global diversified power management company with 2010 sales of $13.7 billion. The company is a leading provider of electrical components and systems for power quality, distribution and control; hydraulics components, systems and services for industrial and mobile equipment;...
  
   Official Website
• Bosch
  Robert Bosch GmbH
  Robert Bosch GmbH is a multinational engineering and electronics company headquartered in Gerlingen, near Stuttgart, Germany. It is the world's largest supplier of automotive components...
  
   Official Website
• Delphi
  Delphi
  Delphi is both an archaeological site and a modern town in Greece on the south-western spur of Mount Parnassus in the valley of Phocis.In Greek mythology, Delphi was the site of the Delphic oracle, the most important oracle in the classical Greek world, and a major site for the worship of the god...
  
   Official Website
• Hilite Industries Official Website
• Saturn Engineering and Electronics Official Website
• TLX Technologies Official Website