My converter seems to lock up at cruising speed occasionally, causing a shuddering and some power loss. No check engine light. After stopping, putting it into park, and then resuming normal driving , it goes away and it may not happen again for a week or longer. Do I need to replace the transmission? Could i just change the trans filter, fluid, and add some Lucas Trans fix and take my chances? Also I've been told there may be a converter lockup switch that sometimes goes bad. Any other ideas?

 

The torque convertor is supposed to lock up at about 35 mph in third gear under light throttle conditions. What you are feeling might be an unlocking, which probably shouldn't be occurring. The clutch engagement is controlled by the trans computer.

When was the last time the fluid was checked/changed? If you don't know, then the answer is probably never and it's probably overdue. This transmission, like most modern transmissions, is sensitive to fluid condition and level.

Changing the fluid and filter would be a very good step, and might solve your problem. Skip the additives for now, go with ATF +4 fluid. Get the fluid clean and full, and see how it works.

If the torque convertor clutch has gone bad, you are looking at an expensive repair, because you'll have to replace the torque convertor, which means pulling the trans out of the car.

 

That's about what I figured. I've owned the car for three years now and have put a pile of money into it, ( timing belt, water pump, plugs, wires, coil, exhaust, rotors, ball joints, and a/c components ) but I don't know if the fluid and filter have ever been changed. So that will be my next step. If the car wasn't in as good a shape as it is I'de get rid of it, seeing it has 220k on it. Thank you for your response! Cheers!