I have a '92 Dakota 4wd with limited slip (Posi) rear, which after
running for over a half an hour at highway speeds starts to bind up and
pop the rear axles while turning even slightly.  This is a loud binding
and popping from the axles as the clutches release, is there any way to
stop this from happening, I'm worried that it will damage something.  It
doesn't seem to affect performance because I'm getting pretty good
mileage for a 5.2 around 18-20 mpg highway.

I've checked the fluid level in the rear and it is fine, also added
friction modifier thinking it might help.  Is it possible to have too
much friction modifier in the rear, possibly causing the binding?  Does
the modifier help the clutches to grab?   I am thinking about draining
the rear lube and replacing it with regular lube without the friction
modifier.   Or does the rear clutch pack need adjustment or shimming?
If so, how is it done?   Any advice appreciated.  Thanks.  Tom.