Weird shake/shudder on my 1997 Silverado

[torranosaurus]

Hello.
I have a 97 Silverado 5.7, auto. 2 wd. At start up and idling, the truck has a shake/shudder. Looking under the hood, the engine is smooth and still. Previous owner said he replaced u joints, and flushed the tranny. I am suspicious that the converter is going out. It seems to sound kind of loud at takeoff as if it is taking a little longer to shift to second. at higher speed it is smooth.The truck has 229000 miles. I just bought it so do not have any history on it. Enine seems just fine, but when you start it, the whole thing shakes.

Any ideas?

[gmtech4]

wrong forum,it'll get moved

[Chris]

Moved. Took the fun away from Ryan

 

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[Friz2]

My '95 will shift at a higher rpm until it warms up bit and I have always had a slight vibration at 35-40 mph. Mine also seems to go through distributor caps at a fast rate. They just corrode up and get replaced twice a year.