FREE ADVICE ONLY.

Often the intermediate steering shaft in the Camaro, Firebird TA, Some Chevelle, El Camino . the upper knuckle housing will run low on grease or run dry from engine heat.. go hard due to lack of use etc..

They are not meant to be rebuilt as the boots are locked in ..but if you have a clunking noise in the top of the shaft.. consider carefully drilling a fine hole in the inner housing side.. as shown below on two we just did...tapping a thread in and putting a grease nipple in.. and pump it with a good automotive grease..

Gets rid of the most common clunk.  Mind you if the knuckle is worn out.. consider the options of replacing it altogether..for safety sake.