Steering so stiff

Hi

If the oil has not been changed on a regular basis ( every 2 years )  and the filter this could be the problem

or more serious if the swivel bearings in the axle are dry or seized ( not a service item) must be replaced

moving  the adjuster on top of the steering box can only be done by degrees ( one mil at a time ) and may cause a leak from the bottom of the box when the dirty section of the pitman shaft pulls through the pressure oil seal located in the bottom of the box

try the oil and filter ( located in the bottom of the reservoir) first then jack up both front wheels and rotate the steering wheel fully left and right ( this will take the weight off the lower swivel bearing ) if steering is easier with wheels in the air then the bearings are degraded and need changed

Bigblock has hit the nail on its, there is a universal jointed knuckle on the lower steering column towards the steering box. 

This, as it is exposed to weather can clog up, steam clean the joint and apply penetrating oil initially, work the steering lock to lock and finish off by applying some engine oil or similar thicker oil at the joint and regularly oil this joint every three or six months intervals. 

Please note there is a similar knuckle mounted on the upper column shaft to be found inside the vehicle nearer to the pedals, do lubricate this joint too.

The knuckle described is the most probable cause of the steering stiffness do check the hub bearings and king pin bearing with the front axle jacked up and using axle stands; turn the wheel lock to lock. If need be, disconnect the knuckle to  help isolate the stiffness. 

If you are intent to adjust your steering box, make a mental of where you start so if things go  wrong you can at least go back to where you started, hence the minute adjustments. There is 50:50 chance of developing or worsening drop arm oil leaks as a direct result to adjustments. The drop arm surfaces get pitted easily and can be part of the leakage problem. Renewing the drop arm seal is not an easy task, you will need a drop arm puller fit for the purpose. 

Before renewing your seal (several sizes available) your are advised to fill in the pits on the drop arm shaft; a suggestion not personnaly tried out is to fill the pits with body filler and finely sand down or lead/tin fill the pits.