5r55e Flashing O/d Light

[bustdnukls]

I have a 99 Explorer XLT 2WD and last June added a 98 Mountaineer A4WD. I rebuilt the valve body on the XLT (Transgo kit, new EPC, etc.) and solved this problem, so when I bought the Merc, I went through the same routine and added a new TCC, just for good measure. Now the Merc transmission shifts smoothly through all gears. The problem is that after about 10-20 miles of local driving, the O/D light starts flashing. The tansmission seems to stay in O/D and shifts fine. I haven't put my pressure gage on it to test the stall pressures yet and can't read the codes myself. The light stops flashing after the vehicle sets and cools down. Since the symptom seems to be associated with warmup, I was just wondering if a failed temperature sensor could be the cause? I also experience a rumbling or growling sort of sound/feel on acceleration in first and second gear and wonder if the torque converter may need to be replaced? I don't sense any slippage.

 

[glfredrick]

Without codes, it will be next to impossible to diagnose your problem, but I'd be very suspicious of the forward sun gear. With your model transmission (unlike the A4LD that preceeded it) application of OD gives you 2nd gear. That means that the forward sun gear is running in 2 (OD). When they start to go bad, they generally give an overspeed code which causes the light to flash.

Your indication that there is a rumbling might be a sign that the above is true. If so, only a rebuild will help.

I'd probably pull the pan and check it for metal if it were mine.