My dad is 73 he stopped taking predisone 4 days ago and is constantly sweating. Is this normal?

No. Was he on the Prednisone for a long time (>3 weeks) prior to him stopping? He could be having withdrawal symptoms. More common withdrawal symptoms include: severe fatigue, weakness, body aches, and joint pain. I would give the health provider who prescribed him the Prednisone a call.