Hi, I am new to the forum and I am a complete newbie when it comes to the E350 van. I am having steering issues. I get the dreaded sway/play. I have 240k miles on the van, bought it at a very reasonable price from a limo company, had it for 3 years and now I believe I need to replace parts related to making the van steer properly and not get a heart attack every time it goes all over the place when traveling at freeway speeds. I would like to ask for help on what parts to purchase to replace whatever needs to be replaced to get my van working/steering properly again. Thank you very much in advance!

 

They will wander when there is not enough +caster. The Ford specification for caster is very broad, appox +1.5 to +6.5. You want the caster set greater then +5 for highway speeds. It seems they ship them from Ford in the range of +3 to +4 which is OK for city driving.
E350/E450 Handling Problems are caused by too little + CASTER

 

First , see if you actually have any bad parts , if not
second , check alignment