TH-350C lock up issues

I have a 1983 Silverado C10 that feels like the torque converter locks up even with the solenoid unplugged. Is that a auxiliary valve body issue or the converter itself. Any help appreciated. Trans is a TH-350C.

Sometimes its hard to tell if it is the converter locking up or if it is going into overdrive. You can try plugging it in again to see if that changes anything but at any rate leaving it unplugged for any length of time is not a good idea. If you have converter problems and it blows, it will send particles all through the transmission requiring an overhaul. Its better just to replace the converter or solenoids if that is a problem.

It doesn’t have overdrive. It has 3 gears and a lock up converter. Either way the converter still locks up unplugged and I’m wondering what makes that happen with no power going to the solenoid.

The problem might be that the solenoid is stuck open.

So hydraulic pressure is being applied to the torque converter clutch when it shouldn’t be.


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Wouldn’t the truck stall when it comes to a stop if it was stuck open?


That occurs when the solenoid is stuck closed when coming to a stop. It doesn’t release the hydraulic pressure from the torque converter clutch. So it’s like stopping with a manual transmission in 4th gear without stepping the clutch.

The vehicle stalls.

If you unplug the solenoid valve, the TCC shouldn’t operate at all.

But yours does. So it tells me the solenoid valve is stuck open.


Ah. Gotcha. Makes sense now. Thanks for the info.

How difficult is it to remove the solenoid? With it sitting on the work bench the problem might be obvious.

Not hard at all. Two bolts and two wires it looks like.TH350 Shift Linkage Inside Transmission2LR

This article might be helpful for you.

Hey Tester … that is senseless.

You have said that the solenoid being stuck open causes hydraulic pressure to be applied to the torque converter clutch when it shouldn’t be … and that the solenoid being stuck closed is what causes the torque converter clutch to not release, causing the vehicle to stall when stopping!

So … the solenoid stuck open = TCC always on
the solenoid stuck closed = TCC never off


Who cares, open or closed? The point is if the solenoid sticks and the lock-up does not release, the car will stall when coming to a stop. Just like not pushing the clutch in on a manual transmission.

Used to be a fairly common issue.

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