It is very common for the Chevy ranging in the years between late 70's to the early 90's with tilt steering to have the 2 bolts inside the steering column where the pivot knuckle is located to loosen off causing the steering wheel to be loose. The fix to this problem isn't simple. You are going to have to pull the steering wheel and upper assembly apart and lock-tite the two bolts which hold the pivot assembly in the column.