K310, K310F, K311, K311F, XB-20LN, AWFCX18

The Aisin K310/K311 family is a continuously variable transmission (CVT) developed primarily for compact and medium-sized Toyota Group vehicles. Aisin identifies the XB-20LN as a CVT, while transmission parts catalogues cross-reference the K310, K310F, K311 and K311F with the XB-20LN/AWFCX18 family. The transmission uses a metal push-belt operating between variable-diameter pulleys, together with a torque converter and electronically controlled hydraulic system to provide continuously variable drive ratios.

Specification: Continuously variable transmission (CVT) • Aisin/Toyota K-series • K310/K310F/K311/K311F • XB-20LN/AWFCX18 family • Metal push-belt CVT • Variable primary and secondary pulleys • Torque converter • Electronically controlled hydraulic valve body • Front-wheel-drive and four-wheel-drive variants • K310 primarily associated with 1.5-litre applications • K311 primarily associated with 1.6/1.8-litre applications • Multiple final-drive and calibration variants.

Commonly fitted to selected Toyota Corolla/Corolla Axio/Fielder, Auris, Avensis, Allion, Premio, Wish, Ractis, Verso-S, Vitz/Yaris, Corolla Rumion, Porte and other Toyota applications, with the related XB-20LN also appearing in the Subaru Trezia. K310 and K311 variants differ according to engine, drivetrain, model year and market, so the vehicle VIN, complete transmission code and individual component or valve-body identification should always be confirmed before ordering replacement parts.

Common Faults

Common problems associated with the K310/K311 family include primary and secondary pulley bearing wear, hydraulic pressure and valve-body faults, torque-converter lock-up problems, CVT belt/pulley wear and fluid-related deterioration. Typical symptoms can include bearing whine or rumbling, juddering, delayed engagement, poor acceleration, abnormal engine speed during acceleration, transmission warning lights and CVT ratio or pressure-control faults. Parts catalogues specifically identify multiple primary and secondary support bearings for this transmission family, making correct diagnosis important before assuming that a driveability complaint is caused by the belt or valve body.

Common Fault Codes