Solid axle 4x4 has an intermittentgroan when descending steep grades while in 4wd. I think this is the u-joints in the front axle halves but can't elminate the front differential or the xfer case.Checked front drive shaft u-jointsand they seemed free.

Want to confirm before taking the front axle apart. Any ideas on how to be sure before tearing things apart?

Thanks

Monte