Originally Posted by TriX5

Florin , here is my $0.02.

At 93k miles my '03 4.4i started to make a whining/grinding noise that I located to the area of the Torque Converter. I had no Fail Safe message and no slippage.

Changing the fluid fixed it briefly but then the noise returned and it started to slip going uphill but still no error message. The downshifts started to get very rough and also 1-2-3 shifts seemed rough at that point.

I took the transmission off and found the bearing in the Torque Converted had failed. At that point small debris showed up in the pan and I decided to overhaul the transmission as well. I found one broken O-ring in one of the clutch actuators which may have been because of the debris in the transmission but I cannot be certain of this. Some of the O-rings seemed brittle to me but the friction disks all seemed perfect and no problem with any bearings either.

Just to be sure I changed one needle bearing in the A/B clutch and the main output bearing as well as the friction disks. In addition, I overhauled the control unit but it seemed a bit superfluous. I refilled with fluid from the dealer. So far the car is perfect, I did a couple of 300 mile dashes with it. It shifts very smoothly and is even quieter than before.

So, I think the problem was precipitated by the failure of the torque converter and I am pretty sure that any subsequent problems were caused by this. I am tempted to say this might well be at the heart of most ATs going bad but I clearly have no scientific basis for that. I will probably refresh the fluid every 30,000 miles from here on (just a drain and fill).

Best, YMMV :-)