What you said, front U joints. Simple to check. Jack up one front wheel of the truck with the steering turned all the way either left or right. Try and rotate the wheel by hand. If it's hard to do, there's your problem, then do the other side. There is a company in the US that makes CV joints with the axle for 2500/2500 RAMs similar to these. Get them installed and the problem doesn't come back. The ones I saw were around $500 and a direct fit for newer RAMs. https://www.rcvperformance.com/axlesets/dodge/dodge-ram-2500-3500-rcv-axle-set.html