torque converter issues

joe_mnSeptember 21, 2009

98 grand prix gtp. 120k miles. i notice at steady highway speed the rpm will jump up 300revs or so and than go back down. converter locking/unlocking? does not do it all the time. tech said converter and not tcc. have not scanned it yet. would you notice any converter issues around town at say lower speeds? 30-40mph max? or is this a highway issue? only had car for 3-4 months. seems to shift fine otherwise. i have been fixing lots of little things, coolant leaks, suspension bits and pieces. i guess any new used car is a learning process.

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i go to a grand prix website. i found a thread where someone rebuilt a trans and included about 100 pics. every step of the way. he inspected many parts and happened to show the TCC components. he showed a kit that sonnex? makes for repairing various parts of the trans. seems the seat for the ball of the solenoid plunger can wear. his point was that the fluid pressure can bleed off at this point and perhaps cause the TC to drop out. i am not going to drop the trans myself. its just a little more info for finding multiple causes of one problem.

    Bookmark   September 22, 2009 at 5:01PM
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Your symptoms has the earmark of the lockup clutch dropping out and then later, locking up again. Causes are multiple, one of which is the engine controller receiving a signal of a drop in manifold vacuum.

    Bookmark   September 22, 2009 at 5:22PM
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Sorry that I am pressed for time right now Joe, but you are on the right track. TCC "chuggle" can be very annoying, and the Sonnex kit is one way to deal with it. But only if wear in the valve body assembly is the cause. Many times the problem can be dealt with by replacing the solenoid if it is failing, and/or software update in the PCM, and/or some other input to the PCM that could be causing it to decide to unlock and then re-lock the converter. BTW it's tight but the valve body can be serviced without removing the transaxle, but you need a hoist and an experienced technician to accomplish that trick. IMO.

    Bookmark   September 23, 2009 at 8:09AM
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did i mention the car has a "tuned" computer since it has a smaller pulley, colder plugs, lower temp thermostat? it has the performance shift mode for the trans also but i have no idea if the pcm tune also tweaked some trans functions. my son says the car sometimes will stutter on the highway when he applies more throttle. sounds like the engine is bogging slightly till the trans unlocks the TC? yes, dropping from 4th to 3rd at highway speed can be annoying with light throttle applications.

    Bookmark   September 23, 2009 at 10:00AM
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