Broken Engine Mount...

The last off-road adventure to Lake Mountain in the Blazer had resulted in an unknown clunking noise coming from underneath the front-end of the truck. It has been in vain lately trying to locate and pin-down the source of the racket. Plus the noise only occurred while in four-wheel-drive and then only in low-range under acceleration. I thought it was the front axle or the transfer-case itself. After many crawls underneath, inspecting every bolt, joint and component I finally had the idea to check the front drive-line yet again. Upon inspection I found it to be intact, the u-joints tight with no play and the slip-yoke to be in good condition. The thought to check the crossmember just underneath the driveline came to me, so I grabbed a flashlight and wouldn't you know it, the driveline under load was being forced down towards the crossmember, grinding a concave grove into it, thus causing the noise. I then also determined the root cause of the driveline contact was a broken passenger side engine mount allowing the engine to sag downwards, tilting the transmission and transfer-case to the right. Since the driveline is on the right side of the transfer-case, the driveline was moved down in excess of more than an inch, impacting the crossmember. A six dollar part was causing a noise that I had thought was going to be very, very expensive. Next time I'll know to check all of the smallest incidentals before condemning the big ones.