After I did my poly bush suspension and dealer did the alignment, one of the alignment bolts ( drivers upper rear) I had, the clunk clunk, they made it right free but I had to lie under truck while wife changed gears to see what it was

The nut on that location is hard to tighten due to location of the cat, that's me not the dealer saying it lol

 

My guess was one of the front upper control arm bolts wasn't torqued properly.....like you said it's a PIA to get too! I crouched next to the truck to see while my GF switched gears, but couldn't tell. It did make the noise while going from access mode to off-road too. Just couldn't get it to do it every time. I may take it to the dealer to have them diagnose and fix...for $1,000,000. Sick of dealing with the thing right now. Seems to always be something with this thing.

 

If its an alignment bolt it will also start to do it when you hit gas and brakes, mine had almost fell off

 

Took it to the dealer. Took about 3 hours to find the issue, but they "repositioned the main skid plate" and that fixed it. Not hard to do. I figured I would get charged at least the min diagnosis fee, but they didn't charge a dime.

 

That makes no sense , oh well if its fixed and free roll with it lol