Inspect them or have them inspected! If Your rig bounces when going over a railway crossing ,they likely need to be replaced.
A sharp cracking noise may indicate that one or more Bushing has failed.
If they appear greasy they may be leaking.
It is a 1992...I personally would replace them all regardless. It will improve the ride and Your safety!
Rob & Jean
98 Dutch Star Diesel Pusher ..07 Honda CRV AWD