JUST got this 2003 xlt van with a 5.4 and 45,998 miles it came from a nursery school , it had off road mud tires and chopped bad in front .
The tire should be 225/75 /16 so i changed the frt to 245/75/16 bridgestone V ribs and the rear has for now 225 /75 /16 off roads mud untill i can do the rears . the shop did not ballace the rim ...... NOW i get a huge shake at 40_55 mph , im hoping the get the front ones ballanced and have that fix this shake , at worst it could be the steering box ? Alignment ?

 

Fronts were rotated to the rears? or rear are original placement for the MS tires?

Balance is always a first step,, or, if the rears are/were balanced rotate them to the front and see if it corrects the shake. With relatively low mileage, and the given the speed the shake develops, sounds like a balance issue..

 

what i had was real worn mud choppy tires up frt 225/75/16 all the way around the back tires show no wear .
I used 245/75/16 in the frt bridgestone V ribs up frt . The shop did not ballence them .

 

Sounds like it could be shot ball joints. I know Ford had issues with ball joints in the mid 2000's. That'll eat up front tires and cause vibration. Best practice to change wheel bearings if you find bad ball joints as the wobbling beats up the bearings.

 

Balance the tires. That's a good starting point.

 

OK GUYS this is it , the old mud looking 1950s jeep tires are gone and have LT245/75/16 all the way around it drove 55 mph and felt good no issues . got them all HIGH SPEED ballenced and so far the 40 mph shake the wheel out of your hand is FIXED .
The stock 225/75/16 must turn in sharper . so maybe next time .
My 1993 E350 7.5 to 2003 5.4 E350 Xlt SERVICE VAN UPGRADE IS PROGRESS . ITS A BEAR KNOWING I GOT TO TEAR THE 3 ROWS OF SEATS OUT WITH THE CARPET
Love the old van still better .