More than likely your hydralic system for your throwout bearing is shot, best case senario, fluid and bleeding will fix it. Don't know exactly what set up is in your truck but likely with a truck that old it just might be time to pull your tranny and do your clutch, pressure plate, throwout bearing and check or service your master cylinder.

__________________
'88 STX Super Cab 4x4
2.9 5spd 180,000 miles
Crappy Paint, Worn Parts,
Fix'em as they Break
when Nowhere is Now Here