94 4.0 Torque converter lock up all over the place

[Mackhedq]

So I have a 94 4.0, the TC lock up is all over the place with no rhyme or reason. The transmission is new so I know there's no issues with it.

What I'm experiencing is sometimes driving I'll have OD and TC lock up above 50ish like it should. Shifts just fine and then it will unlock and no TC anymore. Still OD but it won't lock up.

Another issue which is probably related is when my fog/running are on I won't have TC lock up either.

Both these issues I've been chasing for a long time. I've managed to work around them with the TC lock up switch.

 

[Mackhedq]

Well if anyone is wondering I replaced the throttle position sensor, coolent temp sensor and the brake light switch but nothing changed. Then I replaced the oil pressure sender because it's just always been bad and the T/c lock up works again. It must have been feeding enough voltage into the engine to trip up my sensors. Also my gas mileage improved greatly because I fixed my leaky intake boot. There were pinholes all over the ribbed sections.

 

[rumblecloud]

Well...I'm wondering...but not about your fix -- although that is a helpful one.
I have a 94, 4.0L auto, 4x4 and have no Torque Converter (TC) switch or Traction control (TC) switch - at least I don't think I do. Can you post a pic of the switch you're talking about?
Thanks.
r

EDIT: Ok did some reading. Sorry, I'm not that familiar with locking torque converters. Is yours and aftermarket addition?
This is what I found in the Tech Library:

"A4LD – The C3 was modified into the A4LD 4-speed automatic by adding an overdrive gear, which the C3 lacked. This was the first Ford automatic to use an EEC-controlled torque converter lock-up clutch. Electronic shift control for the 3–4 shift was later added, another first, though other gears remained hydraulic. It was replaced by the 4R44E and 4R55E in 1995. The A4LD is a weak transmission, and is known to fail in offroading (4×4) applications. "

I don't go off-roading and my trans is holding up pretty well at 214,000 - knock on wood.

 

[Mackhedq]

Well...I'm wondering...but not about your fix -- although that is a helpful one.
I have a 94, 4.0L auto, 4x4 and have no Torque Converter (TC) switch or Traction control (TC) switch - at least I don't think I do. Can you post a pic of the switch you're talking about?
Thanks.
r

EDIT: Ok did some reading. Sorry, I'm not that familiar with locking torque converters. Is yours and aftermarket addition?
This is what I found in the Tech Library:

"A4LD – The C3 was modified into the A4LD 4-speed automatic by adding an overdrive gear, which the C3 lacked. This was the first Ford automatic to use an EEC-controlled torque converter lock-up clutch. Electronic shift control for the 3–4 shift was later added, another first, though other gears remained hydraulic. It was replaced by the 4R44E and 4R55E in 1995. The A4LD is a weak transmission, and is known to fail in offroading (4×4) applications. "

I don't go off-roading and my trans is holding up pretty well at 214,000 - knock on wood.

The A4LD locks up the T/c to for lower rpms and less loss in the drivetrain. It only does it during 3-4 gear when basically cruising. Easy way to see if it works is cruise at 60mph. Then slowly roll on the throttle and you should see your rpms hold until the truck unlocks the t/c and then they'll climb. Here's the lock up switch tech if you want to read into it. It's useful for towing or long highway stretches.