1988 GT V6
I have done as much research and trouble shooting as I can with no resolution. I was having a shuddering feeling in my car when I went to work (30 min up hill drive) and no real issues on the drive home. Once the shudder starts it is at all speeds and rpms and in P-R-N-D. When I checked the trans fluid at work it was extremely hot and low. I filled to spec and it still seems to be overheating and shuddering now on the way home but it takes a little longer for symptoms. It will not have the shudder if I cool the car and start it, I let it idle for 20 min and no shudder. Its only after I drive it. I did the TCC test while the trans was yet to start shuddering. I was doing 45 and hit the break and the rpm went up 200 as it should. But when I tried it at 55 it was not changing rpm.

I am a little confused as it seems that the shudder is related to the TC or trans vice a engine power issue. But why is it happening in all gears and rpms? Could the TCC solenoid be malfunctioning and trying to engage/ disengage the TCC continuously? Is the TC going bad causing the fluid to overheat and then not function properly when it reaches a certain temperature/ lower viscosity?

Unplug the TCC and see what happens

I tried that today and same results. So i can rule out the TCC solenoid. It is also weird that the shudder was more random and stronger. not it is less noticeable but more reliable for making it happen. could it be the trans and not the TC?

Unplug then is not any part of TC Clutch.

3 speed... Check TV adjustment, otherwise likely internal to the trans.
(4 speed... check TV and vacuum modulator.)

Governor would hose shifting. TV cable w/ iffy adjustment will cause Hydraulic pressure problems.

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So i have some time to look at the tv cable and i see the "D" but it seems to be stuck. Is it hard to press normally or common to be jammed? I dont want to break it. From what i read i need to depress the button and move the small plastic end toward the trans. Then WOT.

I think TV cable should not cause "shuddering feeling."

Adjusting should not be hard.
Adjuster might be block w/ dirt etc. Carefully check. Do Not Force the button or other parts.

I don't have V6 handy right now... Most are this...

Push button so TV spring (inside trans) move cable out of adjustment. Make sure button is same as started. Some cables can move too far then bind the cable and won't adjust w/o "resetting" the button.
Release button
Move TB arm to WOT. Do Not hit Gas Pedal!
Done.

Well i decided yesterday to just poke around the engine to verify that it was not a misfire. well it was.... i am happy that it isnt a trans issue as the cost is much more. what happened is #3 had a spark plug that was not tightened fully. so when the engine was cold it was sealed. then as the engine heated up and the metal expanded it created a gap and then a misfire. i cant get over the fact that i over looked that. thanks for all the help though i am definitely more knowledgeable how transmissions work!