When I finally got my jeep back from the dealer, still not entirely fixed, I crawled underneath to look around.

I saw that they had bolted my front crossmember back on with longer bolts, using 1" thick nuts to lower the cross member and space it away from the frame.

Anyone know why they would do this?
If it was a good idea, is there a better way?
if it was a bad idea, should I put it back?

 

Yeah. They were trying to change your driveline angle. Were you experiencing vibration?

 

I haven't been following what work you were getting done, but was it for more driveshaft clearance? Scroll down to MKJeeps pics where he notched the skid and lowered the crossmember with washers.

https://www.jk-forum.com/forums/modified-jk-tech-2/driveshaft-vs-skid-plate-102041/

 

Did they put a new driveshaft on? If so, they probably did it to try to keep you from ripping the ds boot and or your ds hitting the skid. Thats the only reason I can think of. On TJ's you do this to lower the whole tf case /skid to change the driveline angle. Jk's are not set-up that way.

 

Ok. That's what I figured.
They spent around 3 months trying to figure out what was making noise in 4wd. That must have been one of the things they tried that didn't work.
Thanks for the input guys.