My 95 4x4 just developed a problem, as I drive down the road it suddenly feels like the steering has 'slipped' and I have to quickly correct it to keep it straight. After a couple of these it stops? At first I checked the fluid and it was low, now it is full and still occasionally does it. How serious/expensive is this?

 

If you have the old recirc ball steering not hard at all
There is a nut on the steering box You loosen that and tighten the screw in the center of it then crank the nut back down
It could also be alignment