GM J car, automatic transmission oscillation

Specifically, a 1993 Cavalier. At approximately. 37 mph with light load, the torque converter lockout rapidly goes in/out. The effect is like driving over cobblestones.
The mechanic I take the car to seems to be stumped. The problem arose just after I had the transmission rebuilt, and to say the least, I'm not a happy camper.
Any ideas? I understand it's not *that* unusual of a problem.
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torque converter lockup solenoid went bad, I think, anyone have a 2nd oppinion?

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Paradox wrote:

Would it still work OK at highway speeds? It seems to be, but then I'm not sure what sort of failure modes it would have.
Is this something of the order of replacing the throw out bearing with a clutch replacement (i.e., because most of the cost is for installation)? In other words, should the mechanic have known better and at least asked me if I wanted it replaced?
Thanks for the reply.
Jim Everman

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It's possible the TCC clutch material is actually worn out and you're getting bad shudder/chatter when it tries to engage. Either way, I'd say it's probably the fault of the rebuilder..
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Robert Hancock Saskatoon, SK, Canada
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Jim Everman wrote:

While not unusual, it's not that common either. Several possibilities: bad pump bad seals bad check valves bad valve body bad clutch bad pcm and lastly (but unlikely) ... bad solenoid. It seems to be getting the right signal at the proper time but is not being held into lock. That says to me low pump pressure or bad valve body. It's easy to check the pcm signal to the TCC with a meter or noid. I would do that first... ... or not drive 37 mph.
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Paul wrote:

The mechanic disconnected (the lock up solenoid?), so that the converter won't lock up. That cure the problem I stated, but of course, that's not a proper cure. Would that satisfy the pcm signal check?
Now he is suggesting installing a manual switch to allow it to lock up during highway use. Seems to me they are trying to give me a run-around, so I need some solid ideas to use for leverage. I'm retired and on limited income. Otherwise I'd just get a new car. :-)
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Jim Everman wrote:

Disconnecting the TCC solenoid will certainly elimate the problem of oscillating TC clutch lockups. Around town you will probably never notice the difference. On the highway, your milage will drop a few miles per gallon. Installing a manual switch won't help a leaking valve body but a trans cooler or heavier ATF might. The PCM/ECU/computer sends 12 volts to the TCC solenoid. If the pcm is not sending the signal properly, then the sol might oscillate. Have your mech check the pcm signal. He _should_ know how. Add to my original list: bad speed sensor.
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Paul wrote:

Thanks Paul.. I'll run all this past the mechanic tomorrow. A scary thought is that he mentioned he once owned a car (Celebrity?) that had the same problem and never found the cure.
For what it might be worth, the transmission was rebuilt because it was shifting erratically, or not shifting at all. Prior to that, the lockout seemed to be working fine - at highway speeds at least. The car has roughly 100,000 miles.
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Jim Everman wrote:

Curious, did you have a rebuilt TC put on during the rebuild? Does this rebuilder have any warranty?
Bob
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BOB URZ wrote:

I talked to the manager of the shop where the transmission was removed/replaced today, I haven't been dealing with the rebuilder directly.. but when I mumbled something about the TCC, I was told, "Oh, the TC was replaced". I was also told that the rebuilder did not have a replacement transmission 'on the shelf' so my old one was actually rebuilt on the spot.
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Jim Everman wrote:

Well, its sounds like its time for your "mechanic" to get on the phone to his rebuilder and get things straight. Obviously, something did not get done right. Of course, you mechanic is stalling so he won't have to eat the labor of taking the trannie in and out again.
I am curious to what you paid for the whole deal. From what i have seen, a professionally rebuilt lockup TC alone could be 300 to 500 retail. Bet you it was not changed. Ask lots of detailed questions. And i hope they flushed the trannie cooler lines when they did it.
On the flip side if you have the car, take it to a few other trannie shops for a free diagnosis if they offer it (many do). Don't tell them it was just rebuilt. Play dumb. And then see what they tell you.
Bob
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That's more or less what I told the shop manager today - "I'm not happy, YOU are the one I deal with YOU need to talk to the rebuilder and get this fixed right." We also discussed labor, and my idea is that if it's the rebuilder's fault, he should do the eating.
The bill was right at a grand for the transmission itself, installation was extra. I had the system flushed (I think <g>) about 5000 miles ago. When this problem first came out, I commented to the shop manager, "Well, that sure was a waste.." (the flush).
The free diagnosis is a good idea.. I suspect the shop manager thinks I have already done that since I'm playing less and less dumb when talking to him - thanks to you guys in this group.
Jim Everman
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