I have too much slack in the steering approx., 3/4 turn of the wheel. There are no shims in the housing. Is it possible to have the housing machined to correct the problem?
Your housing isn't likely the problem, it is a worn worm gear or sector. It could also be the bearing at the end of the steering shaft is worn out allowing the shaft to move in and out. You mention checking for shims, have you also had the cover off the top of the pedestal to see how the gears look? I'm guessing that you don't have power steering