Originally Posted by rdusel
Overdrive on the 4t60E is 4th. gear and is actually a "gear" as it is a ratio change produced by locking the 3rd planetary gear set with a pressure band. 3rd gear is 1-1 ratio so it'* a regular gear also created by manipulation of the 3rd planetary gear set.. The torque converter clutch is used to lock the two sides of the converter together, thereby eliminating the slip that occurs during torque multiplying (converting), adding some MPG and reducing heat in the tranny fluid (and transmission). It reduces RPM by about 500 rpms (feels like 1/2 of a regular gear change).
Torque converter lockup will happen in 3rd and 4th gears, usually after the car reaches a decent speed and loading of the motor is low. Taking your foot off the gas on the highway (or touching the brake) will result in the TCC unlocking in case you are going to apply the brake (since it'* easier to stop the car if the torque converter is unlocked and the converter has to be unlocked for the car to idle at a standstill). The TCC will also unlock if you apply a certain amount of acceleration as the torque multplying effect of the converter is used to help accelerate the car. After TCC unlock, additional pressure on the gas pedal will result in a drop from 4th gear to 3rd as the car acceperates better when not in Overdrive.
And yes, solenoids (3 of them I believe) control all of the shifting and locking/unlocking of the tcc clutch by turning on or off tranny fluid flow.
Hope this helps.
wow thanks a lot.
So what would cause a shudder in 3rd gear then around 40mph with minimal throttle? Could that shudder I am feeling be a locking and unlocking of the torque converter since it cannot decide what to do?
oddly I only get a little shudder in 3rd gear, 4th/od is sorta unstable but not as noticeable.
Is this a sign of a failing or weak solenoid?
Or is this just a computer issue like a bad TPS or VSS or some other issue. I know the shudder I get is in 3rd gear when the car is moving and not much throttle is requried at that point.
Highway is not supersmooth either, but there are only problems when it is in very low rpms and just a minor jittery feeling