Need advice Please

I have a 1999 Chevy Venture van. It is running great except for this
squeaking noise. When you turn and hit a dip it squeaks like a
tricycle with a rusted wheel. It also does this when slowing down or
just moving through a bumpy parking lot. It has done this also on a
smooth surface just stopping at a red light. The shocks seem fine
because the van drives very, very smooth.

I took it o my mechanic today and he greased the bushing, and said
that should fix it. Well it didn't. Anyone have any idea what it is? I
have parked the van, and then stood outside of it, and rocked it side
to side, and front to back, and can never hear it. It is coming from
the front of the vehicle for sure. What could it be?