I have a problem with the lock-up clutch in my 1998 Jeep Grand Cherokee which has an automatic transmission and request your opinion of the cause and corrective action. The problem is the torque converter lock-up clutch opens (disengages) momentarily and randomly at steady speed (when above the nor…

Check your brake light switch (On the brake pedal) first. If this switch is not adjusted properly road vibrations could cause it to close which would unlock the converter clutch. Back the vehicle up to a wall, lightly press down on the brake pedal, you should be able to depress the brake pedal abo…

Thanks for the suggestion!! I didn’t think of this before but it could be the solution - I’ll try it.

later models of some cars prevent shifting into overdrive when temps are too low, for polution requirements. also pressures to torque convertor lock up need checking.

The problem occurs in both summer (hot) and winter (cold) conditions. Where is the TC lock-up pressure checked? Is there a pressure tap for this on the outside of the transmission? Is this something only a transmission service facility can do?

One of the most common issues causing a converter clutch to fall in and out of lockup is a faulty TPS (Throttle Position Sensor). I have also seen other things such as faulty trans temp sensor and even noise coming from the alternator which would affect lockup. transman

Thanks for your comments Transman. I would like to check-out/investigate some of the considerations suggested so far but I need a good transmission manual/book for guidance. Can you inform me what to buy and where I can get it?

I assume that you do know that by pressing the brake petal the converter clutch unlocks. I think Transman touched on that.

My Jeep still has the problem with the torque converter clutch momentarily disengaging or at least slipping on level roads at steady speed. As suggested, I checked the brake light switch in the garage and it was OK and I also checked on the highway by holding the brake pedal fully up with a bungie …

Automatic transmission lock-up problem

Maintenance/Repairs

98Jeep January 10, 2009, 5:58pm 4

The brake pedal moves 1/8" before the brake lights come on but there is no adjustment capability for the location of the switch to increase travel before switch actuation. The pedal moves quite hard so I don’t think road vibrations would cause the switch to actuate. Do you have any other suggestions?

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Automatic transmission lock-up problem

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