Overhaul - 4L60/4L60-E: Description
Turbo Hydra-Matic (THM) 4L60 is a fully automatic trans-mission consisting of a 3-element hydraulic torque converter with a Torque Converter Clutch (TCC). Two planetary gear sets, 5 multiple-disc clutches, one sprag clutch, one roller clutch and a band provide friction elements necessary to produce 4 forward speeds, last of which is Overdrive. See Fig 1.
A hydraulic system, pressurized by a variable capacity vane type pump, provides pressure required to operate friction elements and automatic controls. Transmission contains an auxiliary valve body for smoother Drive and Reverse engagement. Temperature switch may be used to apply TCC to prevent transmission overheating. Temperature switch reduces fluid temperature in Overdrive when TCC is not applied.
Temperature switch mounts on valve body and sits in trans-mission pan fluid. See Figure. At normal operating temperature or less, switch is open. As fluid in pan heats to 270-286°F (134-140°C), switch closes to allow TCC to apply until fluid in pan cools to 250-268°F (121-131°C). Heat is reduced when TCC is applied and torque multiplication function of converter is by-passed.
The 4L60-E transmission, uses clutch and band elements which are very similar to the 4L60 transmission. The 4L60-E, also contains electronic solenoids to control hydraulic operations. The 4L60-E does not use a governor valve or throttle valve assemblies. A Powertrain Control Module (PCM) receives signals from Vehicle Speed Sensor (VSS), Throttle Position Sensor (TPS), fluid pressure switch assembly, and temperature switch. These signals help PCM determine when to switch the 2 shift solenoids, 3-2 downshift solenoid, and/or TCC solenoid on or off. The PCM can also control line pressure via pressure control solenoid (force motor).