I recently noticed that my Jeep (2013 Rubi JKU) has a rattling sound in reverese - It seems to occur only between 1000 and 1500 RPM, and only once it has been running for a while (making me think it's an exhaust issue). It sounds like it's coming from the transfer case area, but it's hard to tell. It doesn't occur in park or drive. I've traced the exhaust system/heat sheilds and can't see anything that is loose - although I am certainly not a master mechanic. The teraflex exhaust spacers I recently installed to keep the crossover away from my drive shaft seem to be fine. Any thoughts?

 

Check where the exhaust goes over the axle, maybe in reverse the axle will droop more, and make contact somewhere?