Shudder at light throttle

Larryjb said:

I am presuming that the computer disables the lock up feature of the torque converter in the tow haul mode.
An automatic transmission transfers mechanical power from the engine to the gears through a fluid couple. In this mode, the engine will spin faster than the input of the transmission. This gives the engine more power because the engine can rotate faster. To conserve fuel, a lockup solenoid will make a solid couple with the transmission. In this mode, the engine RPM will drop. In order to change gears, the lockup solenoid must release the mechanical lock.

The lockup is not used in gears 1 or 2 because you normally need the power to accelerate. This is why you won't feel shudder in 1 and 2. Presumably, because you need the power for towing, the tow haul mode probably won't use the lock up either.

The shudder you feel in 3 and 4 is the lockup clutch slipping. The Lubeuard is a friction modifier which will affect the slipping of the clutch.

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Vegasmarc21 said:

Affect in a good way?

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Larryjb said:

What are you asking about having a good effect?

Is it the use of tow/haul? Is it the shudder itself? Is it the Lubguard? I can't answer that definitively. I'm not a mechanic, and I've never tried to pretend to be. I'm only replying to this thread based on my own experience with torque converter shudder.

Use of tow/haul: In some vehicles I learned that disabling the lockup feature actually causes the transmission fluid temperature to increase. This is because when it is not locked up, the fluid itself is transferring the torque to the transmission, and the resulting turbulence of fluid creates the heat. Locking up the torque converter is required to prevent overheating the transmission. I do not know what the effect of continued use of the tow/haul mode on the 5.3L Tahoe would be. I presume that because the tow/haul is designed to be used, that it is safe to use, especially if you have a separate tranny cooler.

The shudder itself: I presume this is harmful to the transmission and will eventually burn it out. You should be able to instantly stop the shudder by lightly tapping on the brake as soon as you experience shudder. The use of the brake should send an electrical signal to the computer to disengage the lockup, thereby stopping any shudder.

Lubguard: I don't know. I have heard lots of good things about DrTranny Instant shudder fix. But I would completely drain the transmission (including the torque converter) before switching from Lubeguard to DrTranny.

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Larryjb said:

Meccanoble,
You're right, that is a horrible band aid solution. I would probably try the DrTranny first, then a tranny flush involving draining the torque converter.

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Vegasmarc21 said:

Can anyone tell me what shudder I have under very light throttle usually on any gear EXCEPT 1st and 2nd gear with about 1100 rpm to 1500 rpm..... Doesn't happen when I start driving when Tahoe is cold and not up to operating temperature. WOT there is no shudder at all. I have a 2011 Tahoe 5.3 V8 with hundred twenty thousand miles.

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Daniel12 said:

I just purchased a '12 from a Carmax here in Austin, and it has about 120K on it and has the exact same issues. I turned it back into Carmax who then took it to a local Chevy shop.

When I get it back (assuming it's actually repaired) I will pass along what they did to it.


a 2011 Tahoe 5.3 V8

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Meccanoble said:

Vegas, thanks for your updates. I swear to you I'm following your feedback closely. Once I feel confident your issues have gone away with no negative effects, I'm ordering some dr tranny as well.

Larryjb, I will try your recommendation but thats a horrible way to have to drive just to stop the shudder. What would be the easiest permanent fix if this was truly a band-aid to the issue?
"The shudder itself: I presume this is harmful to the transmission and will eventually burn it out. You should be able to instantly stop the shudder by lightly tapping on the brake as soon as you experience shudder. The use of the brake should send an electrical signal to the computer to disengage the lockup, thereby stopping any shudder."

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