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Torque converter doesn't stay locked

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Old 12-13-2017, 04:25 PM
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1993C4LT1
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Default Torque converter doesn't stay locked

93s auto's are 4l60s, not 4l60e's. Okay, so my description below.

I notice the converter always locks up at 47mph, whether in D(3rd) or OD(4th). If I tap the gas the pedal, it seems to have a solid lock, because I feel the car lurch when tapped. Don't know how to explain it, but it does have a solid lock. At least I think so. And everytime it is locked, and I let go of the gas, the exhaust makes some nice pops.

It is very consistent for when it unlocks. If I floor the car, it no longer stays locked. Or if I baby the car as if my granny was driving it, it will stay locked. But anything required to have some fun, or pass anyone, it doesn't lock up. Yes, when locked and I tap the brakes, it does unlock.

When it is unlocked, I can get it to lock by getting on the gas enough to pass someone. But once I get back to normal throttle position for highway cruise, it unlocks. Weird, right? Yeah, I know.

So basically, it locks, but won't stay locked. Trans was rebuilt May 2015, have put about 5k miles on it. The converter is rebuilt, not a new one.

Of course, this is coolant brought up to temp. And throttle position values seem pretty accurate, no bogus readings.
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Old 12-13-2017, 06:20 PM
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Originally Posted by 1993C4LT1 View Post
93s auto's are 4l60s, not 4l60e's. Okay, so my description below.

I notice the converter always locks up at 47mph, whether in D(3rd) or OD(4th). If I tap the gas the pedal, it seems to have a solid lock, because I feel the car lurch when tapped. Don't know how to explain it, but it does have a solid lock. At least I think so. And everytime it is locked, and I let go of the gas, the exhaust makes some nice pops.

It is very consistent for when it unlocks. If I floor the car, it no longer stays locked. Or if I baby the car as if my granny was driving it, it will stay locked. But anything required to have some fun, or pass anyone, it doesn't lock up. Yes, when locked and I tap the brakes, it does unlock.

When it is unlocked, I can get it to lock by getting on the gas enough to pass someone. But once I get back to normal throttle position for highway cruise, it unlocks. Weird, right? Yeah, I know.

So basically, it locks, but won't stay locked. Trans was rebuilt May 2015, have put about 5k miles on it. The converter is rebuilt, not a new one.

Of course, this is coolant brought up to temp. And throttle position values seem pretty accurate, no bogus readings.
Which one of these conditions is the correct one?
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Old 12-13-2017, 07:15 PM
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Little bit of conflicting info it looks like, it should unlock when it reaches a predefined load or throttle position setpoint. Not sure how the factory cars were setup, but my trans controller unlocks the converter at a predefined throttle position. You don't want to run a converter that isn't a triple disk lockup under lots of load. It won't like it and will probably blow up.

I got a single disk lockup for mine because i didn't feel like spending tons of money on a triple disk because i only wanted the lockup for the MPG's


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Old 12-13-2017, 07:18 PM
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Ok so before I have the need to pass anyone, the converter will be locked. Of course, when you get on the gas pedal enough, any converter will unlock. And mine unlocks when I punch it, or get on it enough for it to unlock. I know that is normal. But once I am back to normal cruise,(lightly touching the gas to maintain speed) it won't lock back up.

The second part you bolded. That part is true as well. So once it doesn't want to lock back up anymore, I can get it to lockup by getting on the gas more than one would normally. As if you want to pass some cars on the left lane. Not flooring it though, I'd say maybe 1/3 or 1/4 of total gas pedal travel. Once I am back to touching the gas pedal lightly, it doesn't lock back up. Am I making sense, or do you understand what I was trying to say better?

Last edited by 1993C4LT1; 12-13-2017 at 07:22 PM.
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Old 12-13-2017, 07:22 PM
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So after it unlocks, you have to press the gas pedal further than you think you should have to in order to get it to lock back up.

There should be some minimum conditions for the converter to lock, it probably looks something like this:

Throttle position not above: X value
Minimum speed: X value
Minimum trans fluid temp: X value

Whatever those values are, I'm not sure. When I set my trans up, those were key parameters that I had to select for my lockup function.

Could be a lockup solenoid going to ****?
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Old 12-13-2017, 07:26 PM
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Originally Posted by Pwnage1337 View Post
So after it unlocks, you have to press the gas pedal further than you think you should have to in order to get it to lock back up.
Correct.
There should be some minimum conditions for the converter to lock, it probably looks something like this:

Throttle position not above: X value
Minimum speed: X value
Minimum trans fluid temp: X value
I did look at my Throttle position values on the highway when the converter stays unlocked. They all look fine, never saw a high value. All my symptoms are when on the highway.
Whatever those values are, I'm not sure. When I set my trans up, those were key parameters that I had to select for my lockup function.

Could be a lockup solenoid going to ****?
I hope it is that. It has been 100% consistent the past month or so.
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Old 12-13-2017, 07:33 PM
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TCC is supposed to unlock with closed throttle. (Foot off pedal). If your TPS is out of range, perhaps the ECM thinks your "light throttle" is closed throttle, and is commanding un-lock.
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Old 12-13-2017, 08:01 PM
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Back then when it would stay locked, letting my foot off the gas would make the exhaust have some nice pops. When it is unlocked, no pops. My other auto C4 was the same way when the converter was locked, and foot off the gas. I'll recheck throttle position numbers Friday.
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Old 12-13-2017, 09:20 PM
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The 4L60 is not the electronic version. You need to know what activates the lockup. Is there any vacuum associated with lockup? If you had a scanner or a Tech1 you could see when the lockup is activated. The Tech1 can also activate the lockup (standing still) on my 94 but donít know if it works the same on a 93.

I was not aware that is should come out of lockup when you take your foot off the gas but I will check it out when I get the opportunity. My 94 locks at 47 and thought it stayed locked till the brake was pressed. But I can't feel when it comes out when I slow below 47 and coasting.

If I slow and brake for traffic, it will just relock when I get past 47 again.
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Old 12-13-2017, 09:33 PM
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To my knowledge, it shouldn't unlock when off the gas. I agree with you on that. I know the trans is based on TV pressure. But the torque converter lockup is controlled by the ECM. As are all 700r4's are ECM controlled for TC lockup. I do have a scanner, a real one not a code reader.
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Old 12-14-2017, 11:01 AM
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Originally Posted by 1993C4LT1 View Post
To my knowledge, it shouldn't unlock when off the gas. I agree with you on that. I know the trans is based on TV pressure. But the torque converter lockup is controlled by the ECM. As are all 700r4's are ECM controlled for TC lockup. I do have a scanner, a real one not a code reader.
You should be able to use the scanner to check when the converter is commanded to lock up. Then you will know if the tranny is getting the signal and the solenoid not reacting. The tcc solenoid is very easy to replace and occasionally will go bad.
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Old 12-14-2017, 12:43 PM
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Thank you sir. Might wake my azz up super ealry before work tomorrow to at least see if the solenoid is reacting or not. I'll set the log to record, so I can focus on the road.
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Old 12-15-2017, 01:59 PM
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Today was a real interesting day. I set out to get some data for the thread by using my Tech1 and getting some numbers for TCC. I did accomplish that. While coasting or driving after lockup (47) is accomplished, when you get below 43 mph it comes out of lockup.

However I did fine some other things out as well. Over the last year I have had or what I thought was lockup problem myself. I just never chased the problem with the Tech1. I felt like it was sometimes out of lockup when it should have been locked but was only a feeling and never sure except to look at the tach and wonder.

So today as I'm driving above 47 it came out of lockup as indicated on the Tech1. But was even more interesting was the brake switch for the lockup showed open when it should have been closed. This happened several times just driving down the road and thought the contacts in the switch might be high resistance as the switch contact was for the cruise problem I once had. At some point I lifted the brake pedal upward using the top of my foot and the switch closed solid.

So now I'm thinking it may need just a slight adjustment to fix the problem and possible the OP might have the same situation as me.

Last edited by pcolt94; 12-15-2017 at 09:03 PM.
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Old 12-15-2017, 02:52 PM
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Very interesting info, thank you very much. I can't tell on my scanner if the brake switch is open or closed. In TC lockup, should it always read "closed"?

Going to test it tonight, or tomorrow morning. Do you guys think this will let me know if the solenoid is reacting or not?
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Old 12-15-2017, 03:49 PM
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Originally Posted by 1993C4LT1 View Post
Very interesting info, thank you very much. I can't tell on my scanner if the brake switch is open or closed. In TC lockup, should it always read "closed"? YES

Going to test it tonight, or tomorrow morning. Do you guys think this will let me know if the solenoid is reacting or not?
I think your scanner will tell you if its in lockup. Should work that way. In my case I was able to easily see the cause of my TCC drop out. When you drive if you think its out of lockup try raising the brake pedal and see if the RPM drops say above 50 mph.

Don't quote me on this but I think at 50 the RPM should be about 1500 or 1600. If your near 2000 I would think your not in lockup.
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Old 12-15-2017, 04:09 PM
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With my 3.07 gears, 70mph should be 2k rpm. But that sounds about right for 50mph at 1500 or 1600.
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Old 12-16-2017, 09:46 AM
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Just my luck, the scanner wasn't wanting to connect to my phone. Bluetooth. When I felt the converter wasn't locking, I would get off the gas pedal, and push up on the brake. Was only able to push up on it on the bottom of the brake pedal, not the top. Didn't notice a difference.

I guess because of the colder temps(it was 41) the converter seemed to stay locked longer? I was like what? So I got it up to 125 because WOT runs always prevent locking after I am back to normal cruise. But after a few miles, it went back to unlocking once back to normal throttle pressure from my foot.
Like I said, when that happens. I can get it to lock by pressing on the gas like 1/3 or so of gas pedal travel. You can physically see the tach needle drop when I do that.

A part of me just wants to change out the solenoid. But I am not a parts thrower.

Last edited by 1993C4LT1; 12-16-2017 at 09:47 AM.
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Old 12-16-2017, 01:43 PM
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If an auxiliary trans cooler is in use the trans temp lock up switch should be removed.
IIRC the 4l60 TCC will not lock up until trans oil temp is +140*.

TCC solenoid can be bench tested with a 12v battery & air pressure. If there is a temperature function issue it may not show up during a bench test.

Insure the TV cable is adjusted properly.

Good luck
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Old 12-16-2017, 01:58 PM
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No trans cooler has been added to the car. Oil temps were in 190s-200s. Not sure how to check if the TV cable is adjusted properly on a 92/93, it's not set like the earlier cars. Shift points are them same as when trans was rebuilt. It will sometimes chirp 2nd at WOT. And that is with new nitto 315s.
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Old 12-16-2017, 06:00 PM
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I've been reading this with interest. I have a 1994 with a 4L60E and a 3000 lock up TC. How does this differ with my TC? Does it never lock up at less than 3000rpm?
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