01 - Shudder when in gear stopped?

Hey Guys,
Quick question; I'm considering buying an 01 as it's in excellent condition and the price is right . However, I have found one concern, I'm pondering.

It's an automatic and (on occasion) when stopped (in gear), it 'shudders' a bit. I believe it's coming from the rear end, but not sure as I only had a few minutes to go over it. If I put it in neutral it stops, reverse starts shuddering again. So it must (I would think) be in the driveline under load? Knowing almost nothing about automatics (driven sticks all my life) the only things I can think of is motor and/or tranny mounts or torque converter slipping?

Searches didn't reveal anything (to my surprise), and also didn't support my beliefs. So I don't know if I'm totally off-base on this or not :confused1?

I'll crawl under it when I see it again, but thought I would check with you guys, as I'm baffled at the moment .

I had something similar happen in my 01. It only did it once, but it had a nasty burnt smell about the same time. I had the tranny flushed and no more problem.

exactly what does "shudder" mean? Is it a sound or a drop in rpms (miss in engine) or does the tranny slip????????

I get an exhaust vibe that echoes in the interior when stopped and in gear, but no shudder, yeah, explain the shudder.