Sorry this will be a long post.. However I appreciate any help or direction.

Short version. TQ does not lock up. Even if the manual TC lock switch is turned on.

Long version ..

2001 F250 7.3L Has a manual TC lockup switch with light. The light does indicate when the TC locks itself when driving even with the switch off. I never use it.. It was there from the PO. I'm just to lazy to remove it.

History - Had a torque converter implode Sent all it's internals into the trans.. Trans rebuilt. Suncoast Triple disc billet torque converter installed.

7 months ago. Got the trans kinda hot. about 260 degrees going up a long grade. It ended up causing my truck temp to almost go into the red.. Pulled over.. Replaced the coolant that was lost let it cool and ended up finishing the road trip with only 1 other time with the trans getting hot but stopped and let it cool before the truck got hot.. Ended up finding out my radiator/trans cooler was full of mud.. (Stupid ex wife burred it in a mud pit and neglected to tell me.

Fast forward to 2 weeks ago. Buddy borrows the truck. I make sure to tell him not to use the TC switch. Goes out to Pismo with a trailer with a bronco on it. I tell him about the issue I had and to keep an eye on the trans temp gauge. I made the 130 mile trek out there with no issues. On his way home he said the truck would not shift from 2nd to 3rd. Then it wouldn't go into reverse. He said the trans never got hot the whole time this was happening . He also stated he was very ginger with the truck and didn't abuse it. I do believe him. I've seen how he takes care of his stuff and have no concerns on him using my vehicles.

I've had it towed to my transmission shop and they tell me the torque converter isn't locking up and that it caused the trans to burn up and I guess the fluid is shot. They stated they pulled a code and said that the computer isn't telling the TC to lockup. I went to the trans shop today to talk to them and they hadn't had a chance to tear into it yet..

I did start the truck, flip the TC lockup switch on. The red light came on like it normally does when the TC locks however I put it in D and the truck didn't die like it should when the TC is locked up.. I've made the mistake in the past and had it on by accident before and experienced it stalling. The truck was able to move in D with no problems with the TQ lock switch on. That's what threw me for a loop.

So I'm at a loss. Searching here and on google doesn't really come up with anything like the situation I'm having.

Any ideas? Also sorry for the winded post.. Thanks again all.

 

The light just says the Torque Converter is getting the signal to lock up - that's all. There's no feedback from the transmission to say it's actually locked.

 

My guess is that the switch is wired to keep the converter from locking when the switch is off. It ran long enough and hot enough because it wasn't locking that the heat destroyed it.

 

Tugly alluded to what I was thinking. In industrial automation, we have sensors that have an LED that comes on when they are made. But just because the LED is on doesn't mean that the third wire that goes to the controller is good. It can be cut & the LED will still be on.

What I am saying is you may have a broken wire, bad switch, etc going to your torque converter, and even though you may be closing the circuit in the cab, there is no guarantee that the circuit is good thru the torque converter (completes the ground if I remember right?)