Sounds like there's wear on the control valve lever in the gear box. When you turn the steering wheel, you really aren't turning the steering linkage. All you're doing is pushing or pulling on the lever which opens the valve one way or the other to direct pressurized fluid to one side of the power piston. That fluid pushes on the piston which tugs on the steering linkage. The mechanical connection between the steering shaft and steering linkage is simply for a backup for safety in case power assist is lost for any reason, in particular a stalled engine.
What you might try first is to tighten the large threaded ring on the gear box right where the steering shaft goes in. If that has worked loose, (which would be unusual), the lever won't move enough to open the valve.
A rebuilt gear box from an auto parts store typically runs about $750.00 as I recall. You can find one in a salvage yard too but they had a very common problem on full size vans where the pitman shaft would get out-of-adjustment leading to very much play in the steering wheel and wander on the highway. That is adjustable but over-adjusting it even a little can make it worse by causing the steering wheel to bind when it wants to come back to center. It's real irritating to drive it like that.
Friday, March 30th, 2012 AT 1:47 AM