Torque Converter Not Unlocking

[RCJames]

1993 Explorer, 4.0L, Auto, 200K plus, new trans,120K. Was given truck a little over a year ago. After coming back from longest trip, 130 Miles, came off
US-23 onto US12 came to a stop. Transmission felt like was still engaged,
maybe torque converter not unlocking? Called a few trans shops and told
possible cause maybe, solenoid on valve body,(3rd to 4th, or torque converter solenoid, or 4th gear main valve body may have issues. I am
a novice mechanic who has not tackled any trans problems let. What advise can be given/tips about working on the AL4D vavle body. (Trans works fine in all gears, and no engine light on, my problem has only happened 4 times in last month after going over 45MPH and coming to stop, torque conv\not unlocking. Thanks RCJames

 

[mnealuf]

Does truck totally stall of just nearly stall? I had similar issue with 4R70W and it was the TCC. Electrically it was fine (resistance ) so never threw a code. The 4R70W has a hydraulic bypass that unlocks the TC is 1st so truck would nearly stall until it downshifted. If I started it and moved it into 2nd gear would shut right off.

 

[recondude]

Same Issue

On my way to A&M from Houston today, my 93 explorer did a similar thing. It has 168,000 miles and is still on the original transmission. I went up to about 55 and coasted to about 45. Usually the torque converter unlocks at about 50 mph. When I rolled on to the gas at 45 mph, the torque converter was still locked and the engine was running about 1100 rpm. When I got on the gas, it didn't unlock. I let it coast to 35 mph, and at about 37 mph, the transmission shifted down to 3rd, but stayed locked up (it was a harsh shift). When I got on the gas, it shifted to 2nd and the torque converter was unlocked. As soon as it shifted to 3rd, it was locked again. This was all in the overdrive position. It only acted up for about 1/3 of a mile. I never had to stop, so I don't know if it would have stalled. It has never done this before and didn't do it for the rest of the drive (there were about 50 miles left).
Sorry for the long post, I hope mine doesn't do it again, but we'll see. I would appreciate any input on the issue. Thank you in advance.

 

[RCJames]

No the truck does not stall, the RPM stay's the same coming to a stop.
This does not happen every time I go above 45 MPH, I would say during last
month 5 times. I kick it out of Drive into Neutral and back into Drive and
the feeling goes away each time.