Pete, there are two bolts that attach the rigid arm of the axle to the frame. Two at each axle end. They are pretty hefty. I had similiar symptoms, called Europa and they recommended that I use a breaker bar and tighten those nuts on the bolts as tight I could. THey said over time some looseness will develop that permits a "slip" = "pop" under load. I did it and it's been okay since.

__________________
S, J.R. Brown
2000 G500 LWB Obsedian Black
2005 Toyota Tacoma Access Cab Off Road Sport
1993 Volvo 240 Sedan Anthracite
1980 450SEL Champange (owned it for 15 years. Great car)
1986 280GE LWB Anthracite (Sold it and kinda wish I hadn't)