Possible Transmission Trouble.
 

Hello!
I am the proud owner of a '98 Buick Park Avenue, and I believe that I am experiencing a bit of trouble with my transmission.

At/around 40 mp/h on a flat road, I can feel the transmission stuttering as if it were trying to shift gears.
When accelerating in the upper 50's, the same thing happens, however much more violently and noticeable.
When in idle, the car seems to vibrate much more than it used to.

We have had the transmission fluid changed, the filter replaced, and apparently a good amount of sludge removed from the transmission.

Of course, the last thing that we want to do is have the transmission rebuilt, so are there any ideas out there of what this could be and how to fix it?

It sounds like a bad Torque Converter Clutch to me. I'm not 100% certain, but that is my best guess. Unfortunately, that would require a lot of work to replace.

Thank you for the quick reply. I will certainly keep that in mind.

After a little bit of digging around, it might also be a problem with the shift solenoids/wiring. I think they can be accessed through the bottom of the transmission, after the pan and filter are removed.

With a rough idle, maybe it's an engine misfire- plug, wire, injector.

I was just going to ask that same question. What may seem like a trans problem could very well be an engine problem. Sludge in the trans pan is considered normal as long as it isn't too much.
Before you condemn the trans when were the plugs and fuel filter changed last?
Could you have purchased some gas that might have some water in it?
These are usually the first things to check and don't cost a lot of money to correct.

I had the same problem with my 96 PA. I changed everything I thought was causing the problem except the transmission and torque converter. Mechanic said it was torque converter! My brother did some research and went to the parts store and bought a little tube of something called shutter stop. He put it in the transmission and the shutter is gone! By the way my car had 250,000 miles on it and a new transmission and torque converter at 95,000. Runs like a top