Front end clunking on takeoff

Hey everyone, I've got a mystery clunking that I would like some help tracking down.
When taking off from a stop I get a repeated clunking, maybe 2 or 3 dull knocks, which then fade to nothing. This only happens if I accelerate medium to quickly. If I pull away slowly there is nothing. It feels like it is coming from somewhere under my feet on the front end.
I first assumed it was a bad U joint on the front axle, but I removed the front axle and there is no change.
It's not a bad motor mount or transmission mount. All have been replaced recently and still look good. I also changed the dif. fluid and my gears looked fine.
Because of the repeated knocks it sounds like something that turns, which is why I first assumed the driveshaft. Could it be wheel bearings or an axle U joint? Wouldn't these also have noticeable effects at speed or be influenced by turning? Could it be a transfer case issue?
Any ideas would be appreciated.

My jeep:
1994 XJ
189,000 miles
4.0
NP231
4.5" lift
33" tires

I know you have replaced the engine mounts recently, but humor me a little. Pop the hood and have someone press on the skinny pedal with the other foot on the brake so the Jeep won't move and watch the engine. Let me know what happens

What Steve said, hint; most of the time it's the driver's side motor mount.