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This would still seem to be the key.When the FWD fuse is in place the symptoms are gone.
If there's no symptoms with the fuse in, then there's probably torque build-up in the drive train.
When the engine is running with the transmission is in Neutral, the duty cycle signal to the AWD solenoid is held at around 5%, which is very low. At this rate the clutch is probably not capable of transmitting much, if any, torque.
However, when the transmission is changed to a drive gear (D, or R), the duty cycle is raised to approximately 30%; it will go above this depending on driving conditions, but not below.
Normally, 30% should be sufficient to transfer power to the rear, but not be enough to lock the clutch. In other words, at the 30% duty ratio, the clutch will allow some slippage. This is necessary to accommodate steering corrections, bumps, and tight turning, where the front and rear drives turn at different rates.
If there's a "kick" when the gear lever is subsequently moved from D to N, then that could be the release of torque build up as the clutch duty cycle reverts to 5% and the clutch disengages.
The pressure on the clutch is controlled by the AWD duty solenoid in concert with the AWD transfer valve. The solenoid, which is pulsed by the duty cycle signal, directs hydraulic pilot pressure to the transfer valve. The pilot pressure operates the transfer valve which controls line pressure to the clutch. The transfer valve or solenoid could be defective such that either tends to over-respond at the 30% duty cycle rate, maintaining more pressure on the clutch than there should be.
The test for this would be to measure the hydraulic pressure to the transfer clutch at different duty cycle rates. The FSM has the specs, and there's a port on the side of the extension case specifically for this.
I don't have the details for the 2005 4EAT, but I've attached the pressure test page from the 2007 4-speed to provide an idea. The specs might be somewhat different for 2005, but it gives an idea of what to expect. If the readings are significantly higher at lower duty ratios, a faulty solenoid or transfer valve could well be the problem.
If this is the problem, then it seems to me there should also be torque bind symptoms when turning in a tight circle, and I can't explain why that doesn't seem to be the case. Nevertheless, it would probably be worthwhile to better establish if there's incorrect pressure on the clutch before jumping to disassemble the transmission or valve body.
I understand the solenoids in the valve body of the later Phase II 4EAT, including the AWD solenoid, cannot be changed individually. But perhaps someone has found a way.
p.s. when was the last time the ATF was replaced? Did you try draining and filling the fluid a few times to clear the original torque bind symptoms?
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