IDENTIFICATION
Turbo Hydra-Matic 4L60 (previously 700-R4) transmission can be identified by a letter code contained in identification number. Identification number is stamped on transmission case above oil pan rail on right rear side. (Scheme 1) Identification number contains information which must be used when ordering replacement parts.
Scheme 1
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. (Scheme 2)
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 transmission pan fluid. see scheme 37 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 bypassed.
| CAUTION | Ensure transmission contains auxiliary valve body before performing repairs. (Scheme 3) |
Note. See AUTO TRANS DIAGNOSIS - GM TORQUE CONVERTER CLUTCH article in AUTOMATIC TRANSMISSIONS for information on converter clutch system used in THM 4L60 transmission.
