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What prompts tc to unlock

1932 Views 23 Replies 9 Participants Last post by  RichardM
What signals the torque converter to unlock? I know the brake pedal signals it to unlock, and when I tap the brake, it does unlock as it should.
What else signals it to unlock?
When I am just cruising along and I apply light throttle, it just rattles and detonates. I have started just tapping the brake with my left foot whenever I want to pass somebody or speed up.
Next time I drive it, I will see how much gas pedal it actually needs to unlock.
Does the TPS send a signal to unlock?
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Sorry for the hijack:

In my '97 with stock tune, if I give it a surge of throttle at 40 MPH in OD with TC locked, the TC unlocks and won't lock back up. It finally locks up after maybe a mile, but is really resistant to it, ie: you can't make it lockup with throttle input. There are other times I find the TC unlocked in OD with no apparent reason, ie: car not cold, etc.

These conditions are all usually when going up a slight hill. When I work up thru the gears, all functions work perfect, even going up a hill. But if you interrupt it, it doesn't want to go back. The 4th-3rd downshift under acceleration is also clunky with the lockup BS, but these cars are generally that way. The car shifts into OD at 34-35 MPH, very low.

Hopefully have a j-mod in my future with new valve body. Shouldn't have waited this long.

Al, all of that seems normal, from what I remember of the stock tune. If you're over about 25% throttle, it won't re-lock.
I am definitely under 25% throttle, even at almost 0% in an attempt to make it lock, and it won't. It finally does after a long while.

One of the things I found with the tunes I got over the years is that part throttle, low rpm/high load, seemed to always be on the edge of pinging/knock. Most definitely went away during the winter and came back in the hotter air of the summer.
Tuners often forget how many things affect these conditions.
I remember making Jerry W mad asking for a retune after charting out my issues with the same problem. This was compounded by elevation at 6000 ASL.
Eventually I found that the easiest way to fix it was to tune it out myself with my own tuner.
The 1995 PCM had the convenient octane plug input that you could assign a value to pull or add spark globally. I used to pull like 4 degrees across the board and it would go away.
That little change will not be measurable in your daily drive and hardly noticeable at the track.
Having the ability to switch tunes on the fly was my solution. A switch chip setup allowed easy adjustment to conditions back in ABQ.

BTW, a good tuner would be able to tune this out on a dyno if they didn't already have a quick fix from doing it before.
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