'07 Yukon XL Denali - Thump when taking off?

[BSarteSr]

My '07 Yukon XL Denali has a thump when I start off at a light or stop sign. Kinda feels like a motor mount or possibly a U-joint. I saw this thread (http://www.tahoeyukonforum.com/threads/broken-motor-mounts.55790/), but no real diagnosis. I do quite a bit of mechanical work, have 5 other show cars, rebuilt frame off's, so this one is puzzling me? Tried the brakes on in drive test, but motor really does not lift up, got under it and the U-joints don;t seem to be an issue?

Thought I would post here to see if anyone else has an idea where to go from here? Yukon has ~ 130k on it, take pretty good care of it, been doing this for 8-10 months, not really getting any worse, but want to figure out what it is?

 

[Meccanoble]

I had same thump and it was definitely a motor mount. Best test is to hold brake and lightly press gas. If you see engine jump or hear a bad thump, its driver motor mount. I believe you test in reverse to confirm if passenger side is bad. Common issue on these trucks.