Diagnosis & Overhaul - JATCO 3N71B, L3N71B & L4N71B: Description

The JATCO (Japan Automatic Transmission Company) 3N71B and L3N71B transmissions are 3-speed units, consisting basically of a 3 element torque converter and 2 planetary gear sets. The L4N71B is a 4-speed unit, consisting of a 3 element torque converter and 3 planetary gear sets. The L3N71B and L4N71B use a lock-up type torque converter while the 3N71B uses a conventional type converter.

To provide the friction elements required to obtain the desired function of planetary gear sets, the 3N71B and L3N71B utilize 2 multiple disc clutches, 1 multi-disc brake, 1 brake band, and a one-way clutch. On L4N71B, three multiple disc clutches, 1 multi-disc brake, 2 brake bands, and a one-way clutch are used. On all models, the hydraulic system, pressurized by a gear-type pump provides working pressure required to operate friction elements and automatic controls.