JoeDude, if the pitman arm fails to move until the steering wheel has been turned 3 inches, something is wrong inside. Maybe...maybe it could be an adjustment but 3 inches is quite a bit. As others have said your pitman arm should move when the steering wheel is turned even a bit. Try this: pull back on your steering wheel...that is to say pull it back toward you and see how much play exists. It should not move at all, but let's start there.
The Steering wheel does not move at all when pulling towards me.
Good to know about the cornhead grease mixture or if there is a suitable viscosity to be found. It looks to me that the box is fairly dry, and from everything the good folks stated here, it doesn't seem like adding grease will make any improvement. Maybe trying small box adjustments?
