Ok I am OBVIOUSLY MISLEAD when it comes to trans issues and have already had 2 3800 cars with totally dead transmissions.


Ok so I search for Torque Converter Clutch and I get 300 topics.


Most of them involve a shudder at speeds above 35mph

I keep reading misleading posts.

So can someone educate me on how a 4t60 transmission works or describe it briefly?

What I thought I understood about these transmissions:

- They dont actually have a seperate "gear" for overdrive

- Instead of having a gear they use a Torque Converter Clutch

- The Torque Converter Clutch ONLY kicks on in 3rd gear at 50mph+ and kicks down when the idle is alterated, or you take your foot off the gas

- The torque converter clutch "locks" at a certain speed....this is called overdrive when it locks.

- The torque converter clutch SOLENOID tells the torque converter clutch WHEN TO LOCK based on VSS, TPS, and a few other sensors.

- The toruqe converter clutch can only lock in OD postion

- The torque converter cluctch can lock in both OD and D

- The torque converter clutch IS THE OVERDRIVE GEAR






What is incorrect in the above statments

Overdrive is 4th gear. Overdrive is ANY gear with a ratio greater then 1:1, basically it means the engine is turning slower then the wheels due to a tall gear. Things such as towing are very bad in such a gear.

Some 6 speeds in manual transmission cars actually have two "overdrive" gears.

so overdrive does not really have to do with the TCC???

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. While a bad solenoid can cause the loss or poor application of a gear (or the TCC) it'* pretty rare and TCC shudder is usually the result of a failing TCC clutch lining due to the weight of the car, infrequent tranny fluid changes (causing breakdown of the fluid) and the high frequency of TCC lock/unlock cycles that the car'* computer requests.
Hope this helps.
Rob

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

Nice writeup. Good basic info for sure.

on the 97 to newer cars its D 3 2 1 . so the D is still Over drive?

On newer cars with D 3 2 1 then D is Overdrive and 3 is the 1-1 regular drive.
When I had a bad EGR valve I would experience rough, uneven running when the motor was in the 1000-2500 RPM range. That could be you problem. Also, Plugs, coils and wires could also cause the problem as low RPM, high gear (3or4) operation with the TCC clutch engaged will cause an intermittent miss if there is a weak point in the ignition. Low RPMS and high cylinder pressure (load) makes the hardest environment to create a spark.

Also, in my writeup I mentioned that 3 solenoids control the TCC clutch, I meant to say TCC clutch and gear shifting. Only 1 solenoid controls the TCC clutch. Sorry if I confused you, I rteally should stop writing messages at 2am....

Rob