If it's a "errrtch" type of sound, not a constant squeal, then you probably just getting to the bump stop and it's normal. A little unsettling for those around you, perhaps, but it's normal to make a little groan with these guys.

'87 Raider - 2.6L Rebuilt by me, BSE installed.
Superwinch manual hubs. LSD, Squirters and bouncy seat added. Cobra CB w/ PA (PA coming soon). 31x10.5x15 Futura Dakota rubbers; Pro Comp Add-A-Leaf w/ Rancho RS500's in the rear, KYB's up front.