I just went through this on my 1 ton. The lash screw was rusted solid into the lock down screw thing. I could get the lock down loose, but I could not move the lash screw.
I put like three/four days worth of rust breaker on it. Letting it soak for a long time. Then I loosened the lock down screw. Held it with on wrench and the lash screw with a vise grips.
Then...you just squeeze them together and pull them apart. It only moved just a bit each time...but every time I pulled them apart the lash screw turned just a bit more. I could feel when it was getting tight because of rust build up...then I would change direction.
It took a good ten minutes to get the lash screw fully loose....but it was effective. I know have a fully adjusted steering box. This was after the PO told me that a mechanic said there was nothing left to do.
(THANKS TO WRENCHBENDER for saying it was still adjustable. It gave me the patience to work on it.)
As to figure out if it is the gear box or all the connections/parts...I just put my hand around the steering shaft...in the wheel well and turned that. I could see it turning a lot before the pitman arm/shaft out of gear box even started to move. So I knew it was there and not in the other parts.
Dave
