How Do Transmission Bands Work?

by Jason Medina

Anchored to Transmission Case

Transmission bands, which are thin steel (metal) bands with roughened inner surfaces, are anchored to the transmission case, which is the main structural skeleton of a standard transmission. By enabling transmission gear selection and action, transmission bands are a critical component of a vehicle's transmission. Transmission bands are anchored into place by small rivet-type structures called transmission anchors, or simply anchors. These anchors prevent the transmission bands from moving out of place, a condition that would seriously impede transmission operation.

Powered by Hydraulic Fluid Action

Hydraulic transmission fluid, which provides the fluid force necessary to operate virtually every aspect of a vehicle transmission, provides the fluid force that results in transmission band activation. Transmission bands are connected to small fluid coupling devices called servos, which are similar in design to small plunger-operated valves. These servo mechanisms fill with hydraulic transmission fluid in response to transmission torque converter pressure, a process that results in the servo mechanisms exerting increased force against the transmission bands, which results in the bands being locked into place around the transmission drums.

Lock Against Transmission Drums

As the transmission servo mechanisms lock the transmission bands into place around the transmission drums, which are cylindrical-shaped gear rotors that perpetuate transmission gear action and shifting, the transmission bands allow transmission gear action by forming a solid link between the transmission axle shaft and the transmission gears. Each individual transmission gear set has a corresponding set of transmission bands and drums that activate and deactivate to engage and disengage transmission gear action. As transmission fluid flows out of the transmission servos, which disengages the transmission bands from their corresponding drums, the entire process is reversed.

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