GM Drivetrain & Suspension Chassis | Transmission| Driveshaft | Gears/Rear End/Differential | Traction Aids

chattering torque converter

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Old Jun 26, 2006 | 07:03 AM
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Default chattering torque converter

i have a new tt3000 and when i brake stall or flash from a low speed it chatters or rattles and i can feel it through the floor.. what could be the problem?
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Old Jun 26, 2006 | 08:55 AM
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The problem is pulse width modulation in the torque converter apply circuit. It can be programmed out or removed mechnically by adding a spring to the valvebody in the right place.
PWM makes the converter engage very slowly and not completely lock. The stock programming lets the converter clutch slip a little bit at all times to smooth out engine pulses.
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Old Jun 26, 2006 | 08:59 AM
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Does the HD-2 kit set up for an aftermarket converter?
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Old Jun 26, 2006 | 09:27 AM
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Originally Posted by Colby 04
Does the HD-2 kit set up for an aftermarket converter?
No, it leaves PWM intact.
Installing a heavy spring between the pulse valve and the converter clutch signal valve will eliminate it mechanically. In my opinion this should be done for any aftermarket converter.





In non-PWM versions of the 4L60-E that two-piece valve is only one piece. This mod essentially prevents that valve from moving and TCC engagement will feel like a 700R4.

Last edited by James B.; Jun 28, 2006 at 08:33 PM.
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Old Jun 28, 2006 | 08:33 PM
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I just went back and re-read the way you are getting this problem. PWM has nothing to do with it actually. That only affects conditions where the converter clutch is locked up or in the process of locking. Sorry to misslead, your problem is different.

Vibration at full stall speed would more likely be due to a turbine problem. If "tt3000" means Yank Truck Thruster then I'd have to suggest you call them and get an opinion on how to proceed. Keep your foot out unitl that is resolved, the pump won't tollerate much vibration.
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Old Jun 29, 2006 | 08:43 AM
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The converter clutch is not active at WOT (never in low gear) unless you have a custom program installed allowing it to stay locked, or a warped front transmission pump from high line pressure, this will allow line pressure to leak into the converter clutch port in the pump and allow the clutch to start to apply
Also you can also have a slipping clutch pack 3-4 or a bad low roller clutch or overrun sprag all will act as you say.
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