SKF
Bonded Pistons
Bonded pistons are rubber-to-metal bonded seals that function as dynamic actuators within automatic transmissions. They consist of a metal carrier plate onto which an elastomeric diaphragm is bonded; when transmission fluid pressure is applied, the piston moves to engage a clutch pack. SKF bonded pistons are engineered for precise pressure response, minimal hysteresis, and long life in hot ATF. The elastomer must resist degradation from modern synthetic fluids and maintain its modulus across the transmission's operating temperature range. The metal bond must remain intact under millions of pressure cycles. SKF supplies bonded pistons to transmission OEMs as part of mechatronic modules. Their reliability directly influences shift quality, transmission life, and vehicle drivability.
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Trusted by Industry Leaders
Elastomer‑to‑Metal Bond
Vulcanised bond provides a permanent, gas‑tight connection.
Pressure‑Responsive Diaphragm
Actuates clutch packs with precise timing and force.
Hot ATF Compatibility
ACM or FKM elastomers resist modern synthetic transmission fluids.
Consistent Hysteresis
Low hysteresis ensures accurate clutch engagement and release.
Millions of Cycles Validated
Tested under full temperature and pressure cycling.
Integrated Design
Combines piston, seal, and return spring surface in one part.
How a Bonded Piston Replaces Multiple Transmission Components
A bonded piston eliminates the need for a separate O‑ring, anti‑extrusion ring, and sometimes a return spring. By integrating these functions, the transmission becomes lighter, more compact, and more reliable, with fewer potential leak paths.
The Bond That Must Never Fail
If the rubber separates from the metal carrier, the piston strokes without sealing, and the clutch pack does not engage. In an automatic transmission, this means a lost gear. SKF’s bonding process uses a proprietary adhesive system and post‑cure cycle that ensures the bond strength exceeds the elastomer’s tear strength — the rubber will tear before the bond breaks.