Bias ply tires are notorious for wander. It's likely switching to radials will clear up the problem if the alignment is good.

 

Question to clarify-- Am I reading correctly that the angle of the front axle needs to go from high to low when measuring from front to back? If so, what degree of decline should there be? My truck's a little loose (lot of play in the steering wheel). I figure I need to tighten up the worm gear in the steering box, but my truck's also got a slight rake from front to back, putting the front axle on an incline from front to back, and if I'm understanding this correctly, that's the opposite of what it should be?


Confused.

 

The axle should tip back at the top. This produces caster effect that helps keep the front going where it's pointed and reduces steering effort. Some place between 4-6 degrees is about right, go towards the higher end the more high speed driving you do. You can adjust it with tapered shims between the axle and spring, just be sure the centerbolt head is long enought to still index into the axle pocket. Longer headed centerbolts are also available if needed.
If you have a lot of freeplay in the gearbox, a rebuild or replacement may be in order. These are a rather simplistic worm and pinion system that required periodic maintainance that was seldom performed to prevent excessive wear. Best to open the box and clean out the likely congealed goo inside then inspect the condition of the gears and bearings. If they are in good condition, you are very lucky, replace the lube and adjust the lash. Adjusting worn out gears will only make the steering stiff and binding while accellerating the gears deterioration.

 

Mine Also Wanders At That Speed. I Took Out The Freeplay In The Steer Box ,still Has Some Wander With Radials .as Soon As The Weather In New York Gets Warmer I Will Check & Give It The Correct Tow In . I Was Told Is About1/16 To 1/4 . Good Luck Billy C

 

Something else to consider. Grooved highways can cause wander in any type of tire...bias ply or radial.