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2009 Toyota RAV4 - torque converter shudder

two questions; 1. what are the symptoms of Torque Converter Shutter? Or how can I tell if my vehicle has Torque Converter Shutter? 2: What are the consequences, if any, of the automatic transmission fluid being overfull?

The symptom of TCS is that it feels like the transmission is shifting gears back and forth rapidly in the 30-50 mph range. A shop can disable the converter lock-up function, and if the problem goes away that means it is probably TCS. Overfilling the automatic transmission can cause a host of symptoms, depends on the specific transmission and how much it is overfilled.

Sometimes the driver can temporarily disable the lock-up function by lightly stepping on the brakes.

The purpose of the lock-up function is to improve mpg.

Note: When discussing this w/your shop, the symptom is usually referred to as “shudder” rather than “stutter”.

George;

First I fat fingered the keyboard and got stutter vice shudder. My RAV is a 2009 4 cyl. and I do not sense that the transmission is shifting gears back and forth and the tech does not indicate this is happening. What I am experiencing and the dealer says is TCS, is a rattle/vibration in the back of the vehicle that occurs at 1500 RPM with the car in 4th gear (overdrive). I can make the rattle/vibration stop by down shifting to third. Above and below 1500 RPM with the car in 4th there is no rattle/vibration.

I asked the question about TCS as I don’t believe the dealers analysis and your description of TCS only reinforces my feeling that they are wrong and trying to sell a transmission replacement. R/ Paul C.

Sure seems like torque Converter to me. You don’t have to fix it, just have it disconnected. Your gas mileage may be worse, but probably not horribly. I would have it disconnected so you can still use overdrive.

Hi; I guess I’m dumb as I have no idea what to disconnect? I don’t see how you can disconnect the torque converter. I’m sur you mean something else. As the Rav is going in for routine oil change and tire rotation tomorrow it would be a good time to have whatever you are referring to disconnected. R/ Paul C.

I don’t know either the specifics, look up RAV 4 Torque Converter Solenoid location. Unplug that. It is probably inside the pan so you will want it to be done at a shop.

Shifting would have nothing to do with torque converter clutch shudder.
Torque converter clutch shudder can be felt as a mild vibration when engaging or in severe cases a harsh vibration like driving over rumble strips on the shoulder of the highway.

I would have more faith in the technician that inspected your vehicle than someone on the internet that has never experienced torque converter shudder.

If you tamper with the electronic controls for the transmission the check engine light will be on and you might cripple the transmission.

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Hi; I do not feel any vibration when shifting from Park to Drive. I assume that is what is meant by “engaging”. The noise I hear occurs with the RAV driving and in 4th gear and at 1500 RPM. As soon as I change the RPM either by shifting down to 3rd or speeding up the noise goes away. I think as I don’t trust the Dealers analysis I’ll take it to the local transmission shop and insist the tech ride with me and experience the noise in the back end of the RAV which I think is something just hitting a resonant frequency as what I am experiencing doesn’t match any of the characteristics that have been mentioned.

The torque converter clutch generally engages at speeds of 40 MPH and up, strong acceleration or braking will disengage the clutch.

If you are hearing a noise in the back of the vehicle you may be dealing with a rattle.

If this is an all-wheel-drive Rav4 the noise might be from the rear differential coupling.

Third in my guestimatin will stop the TC from kicking in. sounds like a good option to check out.

I’ll have to make note of the vehicle speed at which the noise occurs. My RAV is all-wheel-drive and the rear differential coupling was replaced about 5K miles ago with no impact to the noise. The noise was the same before and after the coupling was replaced. Down shifting to 3rd without changing vehicle speed raises the RPM and stops the noise.

Yes!!! Or potentially taking out of overdrive. I had a Camry that lost a torque converter. My uncle’s BMW had the same problem, he just disconnected it. It was a 2003 five series.

That pretty much settles it in my mind. Let us know what the tech says. Has the tranny fluid ever been changed in this?

Some background info might be useful here. TCS is a relatively new phenomenon. Automatic transmissions require some sort of slipping mechanism that allows the car to remain in D , engine running, when stopped at a stoplight. That’s the function the torque converter (TC) performs, allows the engine to continue to rotate even though the transmission is not rotating. The TC is a contraption very similar in arrangement to one air fan blowing against another. The first one, if powered up and spinning, its air currents will spin the second fan, even though the second fan is unplugged. The key concept is that you can now poke a pencil against the blade to stop the second fan from rotating while the first fan is still rotating as before.

This method worked fine for years and years of automatics. Then the manufactures noticed customers were suddenly buying models based on almost entirely on mpg ratings. They decided one way to improve their vehicle’s mpg ratings was to modify the design of the TC. The new designs works the same as the old one when stopped at a stoplight or going slow, but around 35-45 mph it locks the fans together. Mechanically, the two blades get stuck together. So they always spin at the same speed. When you slow down below 35 mph the two blades have to start spinning independently again, so whatever method is used to stick them together is reversed. The process of the two fan blades sticking together is called “lock up”. It is usually done with an electrical signal, upon command of some electronic module in the car, the electricity then creates a magnet, and the fan blades get stuck together using a magnetic force. When the current is turned off, the blades unstick.

There’s supposed to be some hysteresis in this process. Similar to when your car’s AC turns on, it doesn’t turn off again in 5 seconds just b/c a little cold air came out the vents. It continues to cool for a few minutes at least, before turning off. The TC lock-up function is supposed to behave that same way. It might turn on at 45 mph, but won’t turn off at 44 mph. Instead it waits to turn off until 35 mph. When this hysteresis function fails, it locks at 45, and turns off at 44, that’s what causes TCS. The magnet locks, then unlocks, then locks, then unlocks the fan blades repeatedly, at a rapid repetition rate, which as you might image creates a shudder sensation to the driver.

Torque converter shudder is clutch chatter. If it occurs for only a second or two it is a chatter upon engagement. Some transmissions are particular about the fluid used, manufactures use additives to eliminate TCS.

If the shudder continues as long as the accelerator is press the clutch is slipping and the torque converter will likely need to be replaced.

So far you have not described a torque converter shudder on your vehicle, only a noise but that doesn’t mean that it isn’t failing. Is the check engine light on?

Lock-up torque converters have been around since the 1970’s, in my experience there were more complaint of torque converter shudder 30 years ago than there is today.

Torque converter engagement is commanded buy the PCM or TCM, if it were to command an erratic engagement how could this be the fault of the torque converter?

I’ll grant than in attempting to simplify an explanation how it works I may have over-simplified. @Nevada_545 's follow-up provides the OP the service of a more proper explanation. Let me say it another way: If my car had TCS I’d rather Nevada be responsible to fix it than me.

But none of my cars host that function, so all’s well that ends well I guess :slight_smile:

If gets bad enough it can continue until you let off the gas or (in the case of my Camry) take it out of overdrive.

Going by descriptions of TCS that have been provided I’m quite sure I do not have TCS but something in the back of the vehicle is vibrating at 1500 RPM, 4th gear and between 35 - 40 mph. Above 40 mph noise stops. No TCS is further reinforced by my experience the other day. The vehicle was in park and idling and there was a noise similar to what I hear when driving coming from the rear of the vehicle on the right side. So when I went underneath and pushed up on the muffler (not hot yet) the noise stopped. Did that several times with same result.
Oh to answer the question, the Check Engine light is not on even when the noise is occurring.

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Beautiful!