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Old 09-13-2005, 08:20 PM
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Torque Converter Lockup at Low Speeds

We have installed a TH200 4R trans in a street rod with 3.42 gears and 27 inch tires. We used the GM vac swithch to activate the converter lockup when engine vacuum is high.

The trans was rebuild by a local shop, nothing special, installed a new stock torque converter.

Problem is, the trans upshifts fairly quickly and smoothly under light to moderate acceleration, and in our neighborhood, in gets into OD and locks up the converter whilel still going only 25-30 mph. This locks the engine in at basically idle speed of 800-900 rpm. As a result you can feel a slight bucking or surging as the engine and drivetrain fight for control.

Is there any adjustment to the trans that will delay the lockup till higher speeds. I know that TCI makes a speed related controller, but are there any internal controls? Or can it be adusted via the TV cable/

Thanks,

John

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Old 09-14-2005, 05:32 AM
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200 r4

yes you can alter lock up, but you might have solenoid trouble. 200r4 had trouble with solenoid ck ball inside would not release and lock up will be on top of second gear and that sounds like what you describe.25 mph would be too low for 4th gear shift that alone will lug down the motor,lock up in any manner that low will give you complaints....
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Old 09-14-2005, 06:12 PM
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I've got the same trans and rear ratio in my '86. I played (forever) to get the TV cable adjusted correctly. I couldn't use the "book" method, because I used a fabricated TV bracket. It now shifts into 4th at about 35-40.

I used the TCI lockup kit and installed a off-on switch under the dash. I've noticed that it often doesn't unlock when it downshifts into 3rd or 2nd. I also get a "hunting" action when moderate pressure is applied in 4th. But, I just switch off the lockup.

I agree that you're shifting into 4th too quickly. I would try more adjustment of the TV cable. A little adjustment (e.g. 1/16") makes a big difference.
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Old 09-14-2005, 08:44 PM
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MI2600,

I have already adjusted mine more than by the book, but you have encouraged me to go further. At first the car upshifted from 1st to 2nd at about 3600 rpm under heavy throttle. By adjusting a little past the book, I have moved the 1-2 shift up to 4200 rpm. I have a mild cam in a Olds 350 so not looking for high rpms.

I will go a little further beyond the book and see what happens.

We drove the car a few hundred miles before I discovered this week that the power to the vac switch had come unhooked and I hadn't had lockup at all. After hooking up the power, I noticed this problem at low speeds.

I haven't been able to determine if it is still locked up after downshift to 3rd or 2nd.

Thanks,

John
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Old 09-15-2005, 10:58 AM
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John,

I had a lot of problems, from not shifting to shifting way late. Yours seems to be shifting late too. You shouldn't have to go over 4000 rpm for a shift. I kept adjusting SLOWLY, in very small increments, so that more cable was pulled from the trans when the carb is at idle.

It can be frustrating.
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Old 09-15-2005, 06:05 PM
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MI2600,

Mine is not shifting late. Under light throttle it upshifts very quickly and is in OD by 30 mph. I like the way it shifts except for the converter lockup coming in at low rpm.

It is only under full throttle that it stays in first to 4000 rpm.

But, today I moved the TV cable one notch closer to the firewall and could tell the upshifts are delayed a noticeable amount. This would be better for more sportier driving, but may hurt gas mileage a little. However, this didn't affect the converter lockup. At light throttle I still get into OD before 30 mph and the converter locks up, dropping rpm to about 900 and creating that surging/hunting sensation.

I guess it will require something internal to the trans, maybe solenoid as was suggested, to delay the shift point or converter lockup.

John
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