No lockup in TH700-transmission
#1
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Car: 1988 Trans AM GTA
Engine: 350 TPI
Transmission: TH700
Axle/Gears: 3.23
No lockup in TH700-transmission
Hi everyone. I have a 1988 Pontiac Trans AM GTA with the 350 TPI and the TH700-transmission. I would be grateful for some help with my TCC, because I have no lockup in the car.
Transmission shifts fine through all the gears in both OD and regular D but there is no lockup occuring. And slightly touching the brakes when crusing on the highway does nothing to the RPMs.
I have searched a lot about this problem and if I understand correctly first step is to check with a test light in the ALDL between terminals A and F with the ignition on. It should light up and then go out when pressing the brake. Mine does neither. Doesn't light up the testlight and pressing the brake does nothing.
Voltmeter on the other hand, gave a reading of about 11,6 volts. (with the ignition on). Pressing the brake doesn't really affect the reading, it drops a few decimals, propably because of the brake lights illuminating but nothing else happens.
Cruise control works fine and turns off when touching the brake, so brake switch seems fine?
The connector at the transmission also had similar readings when I measured it with the voltmeter, but again pressing the brake does nothing.
Am I doing something wrong here? Because since there is voltage shouldn't the TCC always be locked, if pressing the brake does nothing?
Any recommendations for what the next steps should be?
Transmission shifts fine through all the gears in both OD and regular D but there is no lockup occuring. And slightly touching the brakes when crusing on the highway does nothing to the RPMs.
I have searched a lot about this problem and if I understand correctly first step is to check with a test light in the ALDL between terminals A and F with the ignition on. It should light up and then go out when pressing the brake. Mine does neither. Doesn't light up the testlight and pressing the brake does nothing.
Voltmeter on the other hand, gave a reading of about 11,6 volts. (with the ignition on). Pressing the brake doesn't really affect the reading, it drops a few decimals, propably because of the brake lights illuminating but nothing else happens.
Cruise control works fine and turns off when touching the brake, so brake switch seems fine?
The connector at the transmission also had similar readings when I measured it with the voltmeter, but again pressing the brake does nothing.
Am I doing something wrong here? Because since there is voltage shouldn't the TCC always be locked, if pressing the brake does nothing?
Any recommendations for what the next steps should be?
#2
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Car: '83 Firebird (T/A Clone)
Engine: 350 carbed with L-69 components
Transmission: 700R-4 w/2000 RPM stall converter
Axle/Gears: 10-bolt/3.73 ..
Re: No lockup in TH700-transmission
The lock-up solenoid in the transmission could be bad. I had to replace mine...
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Car: '89 Formula
Engine: 355
Transmission: 700R4
Axle/Gears: 9 bolt
Re: No lockup in TH700-transmission
Am I doing something wrong here? Because since there is voltage shouldn't the TCC always be locked, if pressing the brake does nothing?
You could check for power at the solenoid with a test light or meter with the brake not depressed. That would rule out the switch.
If so, it could the solenoid itself or connection on the ground side.
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T.L. (07-31-2024)
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Car: 1988 Trans AM GTA
Engine: 350 TPI
Transmission: TH700
Axle/Gears: 3.23
Re: No lockup in TH700-transmission
I am leaning towards just buying a new solenoid at this moment, and hopefully it will fix it, they are so cheap anyway. Since brake lights work and cruise control shuts off when applying the brakes, it should be the solenoid, right?
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Car: '83 Firebird (T/A Clone)
Engine: 350 carbed with L-69 components
Transmission: 700R-4 w/2000 RPM stall converter
Axle/Gears: 10-bolt/3.73 ..
Re: No lockup in TH700-transmission
Yeah, the solenoid is cheap but ATF is expensive these days (LOL !!!)...
#6
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Car: 1988 Trans AM GTA
Engine: 350 TPI
Transmission: TH700
Axle/Gears: 3.23
Re: No lockup in TH700-transmission
#7
Re: No lockup in TH700-transmission
Hi everyone. I have a 1988 Pontiac Trans AM GTA with the 350 TPI and the TH700-transmission. I would be grateful for some help with my TCC, because I have no lockup in the car.
Transmission shifts fine through all the gears in both OD and regular D but there is no lockup occuring. And slightly touching the brakes when crusing on the highway does nothing to the RPMs.
I have searched a lot about this problem and if I understand correctly first step is to check with a test light in the ALDL between terminals A and F with the ignition on. It should light up and then go out when pressing the brake. Mine does neither. Doesn't light up the testlight and pressing the brake does nothing.
Voltmeter on the other hand, gave a reading of about 11,6 volts. (with the ignition on). Pressing the brake doesn't really affect the reading, it drops a few decimals, propably because of the brake lights illuminating but nothing else happens.
Cruise control works fine and turns off when touching the brake, so brake switch seems fine?
The connector at the transmission also had similar readings when I measured it with the voltmeter, but again pressing the brake does nothing.
Am I doing something wrong here? Because since there is voltage shouldn't the TCC always be locked, if pressing the brake does nothing?
Any recommendations for what the next steps should be?
Transmission shifts fine through all the gears in both OD and regular D but there is no lockup occuring. And slightly touching the brakes when crusing on the highway does nothing to the RPMs.
I have searched a lot about this problem and if I understand correctly first step is to check with a test light in the ALDL between terminals A and F with the ignition on. It should light up and then go out when pressing the brake. Mine does neither. Doesn't light up the testlight and pressing the brake does nothing.
Spoiler
Cruise control works fine and turns off when touching the brake, so brake switch seems fine?
The connector at the transmission also had similar readings when I measured it with the voltmeter, but again pressing the brake does nothing.
Am I doing something wrong here? Because since there is voltage shouldn't the TCC always be locked, if pressing the brake does nothing?
Any recommendations for what the next steps should be?
Last edited by MadelineScott; 08-23-2024 at 03:30 AM.
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#8
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Car: 1988 Trans AM GTA
Engine: 350 TPI
Transmission: TH700
Axle/Gears: 3.23
#9
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Car: 1988 Trans AM GTA
Engine: 350 TPI
Transmission: TH700
Axle/Gears: 3.23
Re: No lockup in TH700-transmission
So, finally found the time and replaced the solenoid which looked original. And now it blows the gauges fuse immediately when turning on the ignition. The same fuse that also handles, of course, the TCC solenoid. It didn't do this before.
What do you guys suggest I do next?
Update:
I think I found the answer here on some Buick Forums.
"Either you have a wire shorted to ground, a bad solenoid (internal short), or the solenoid is wired backwards"
https://turbobuick.com/threads/tcc-r...-blows.448858/
Well, I guess I'll have another ATF-bath during the weekend.
What do you guys suggest I do next?
Update:
I think I found the answer here on some Buick Forums.
"Either you have a wire shorted to ground, a bad solenoid (internal short), or the solenoid is wired backwards"
https://turbobuick.com/threads/tcc-r...-blows.448858/
Well, I guess I'll have another ATF-bath during the weekend.
![lmao](https://www.thirdgen.org/forums/images/smilies/lmao.gif)
Last edited by jpyy85; 08-15-2024 at 12:09 AM. Reason: Found out more information about the issue
#10
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Car: 1988 Trans AM GTA
Engine: 350 TPI
Transmission: TH700
Axle/Gears: 3.23
Re: No lockup in TH700-transmission
Alright, so I finally pulled the pan yesterday and the wires from the solenoid had gotten pinched between the pan. Some new tape on the wires and reassembled and I finally have lockup.
The old solenoid did have a faint "pop" when giving it 12v straight from the battery, but nowhere like the new one. And the old one didn't rattle when shaken, like the new one did. So maybe it was stuck or something.
Enough of the ATF baths for a while hopefully. I bought a 12v oil pump for the second time I pulled the pan. Much easier and cleaner to suck out most of the oil through the dipstick before removing the pan.
The old solenoid did have a faint "pop" when giving it 12v straight from the battery, but nowhere like the new one. And the old one didn't rattle when shaken, like the new one did. So maybe it was stuck or something.
Enough of the ATF baths for a while hopefully. I bought a 12v oil pump for the second time I pulled the pan. Much easier and cleaner to suck out most of the oil through the dipstick before removing the pan.
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Car: '83 Firebird (T/A Clone)
Engine: 350 carbed with L-69 components
Transmission: 700R-4 w/2000 RPM stall converter
Axle/Gears: 10-bolt/3.73 ..
Re: No lockup in TH700-transmission
Glad you got it figured out...
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jpyy85 (08-18-2024)
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