i have a 1989 ford f-150. the steering seems to be 'loose' or 'wanders'... someone said this is normal for that year vehicle because ford used 'twin I beams'... could this be the reason? could it be a drag link, pitman arm, tie rod or loose gear box?? are those things expensive to fix??

 

I would suggest you take the truckto ashopfor a Front End Alignmentcheck. As part of the procedure, the mechanic is to first check ALL front end parts for any defects.
And yes, any of the parts you mentioned (if bad) could cause the alignment to be out of specs...thus possibly causing pulling/wandering. And no, such part(s) replacement (if need be), along with a Complete Alignment isn't normally too expensive.
As forthe I-Beams being the cause..... when carrying a heavy load will cause swaying & wandering.

 

If your gearbox needs adjusted all you need is a wrench and screwdriver and a little know-how. It can cause any wandering you can't find anywhere else in the steering. Also at this point it's probably better to check your "rag" joint (between the column and gearbox).