Guess I can give that a try, though I'm pretty sure it's from the steering knuckle under the dash. Was hoping a GM technician here would weigh in with specifics on what's going bad or needs to be lubed.

 

Could also wrap your hand around the U-joint to feel any vibrations that are making the noise.

 

Well, may have finally found the problem, totally by accident. The steering column intermediate shaft has been replaced twice before (15k miles & 35k miles) under warranty. Recently, I felt that the vehicle was doing the same thing as before, an impact vibration when going over a bump or making hard turns at slow speeds. Local dealer said that maybe Chevrolet might pay for a third repair, maybe not since it now has 72k miles on it.

Did a Google to see what part would need to be replaced and the degree of difficulty. Doing that, led me to YouTube videos how to replace the steering column intermediate shaft but even better, how to remove one end of it and pump it full of grease. Tried it and not only has it removed at least 80% of the impact vibrations, it's almost removed most of the groaning that was going on under the dash. Would have never guessed that the two issues were related.

Going to do it a second time in a week or so and live with that result until the steering column intermediate shaft actually goes out; maybe it won't and I'll just need to grease it every 15k miles. Seems like a design flaw though; a Zerk fitting would make this an easy 30-second maintenance item.

I'll post this as a separate thread so when someone does a search, it comes up quicker than the 'groan' issue originally posted.