98 150 steering

V-6 auto short wb 2wd lots of miles,,frontend tight, bearings good,, no brake poblems..have had this 2 yrs when i got it it pulled to the right..I got it aligned 1st time and was still pulling but not as bad..they did it 2nd time and had to adjust it just about to the point of being too far to the left or as they told me fool the computor??..Now it was great for about 3 weeks!! I dont drive it fast or hard and was only putting on about 100mls a week.. took it back again and it lasted about 2 months this time and pulling again to the right..No wreak history, no damage.everything looks good.. Took it to another shop and they said 98 150tys had pulling problems and they were going to put on some holde type clamps to the tune of $150 plus $60 alignment..But they would not stand behind it if it started to pull again!!!!! Now this thing starts pulling just a lil and gets worse as time go's on,,,but it just pulls so far and never gets worse..it takes righthand corners perfect,,no hands at all..ha ha ..and no I like to go left also and down the road..Have to always keep a very firm grip on the wheel or your off the road in 1/2 a second!!!!