Steer Ahead is an adjustment to put the wheels straight ahead when the steering box is on center. Most steering boxes, especially the later power steering boxes, the pitman can only go on in certain positions. With the stock style drag link, there is no adjustment for Steer Ahead. Later trucks with a beam/drive axle tend to have adjustable drag links to allow for Steer Ahead, they adjust exactly the same way a tie rod does. There really isn't a spec for Steer Ahead, other than perhaps 0. If it's not correct, then the front wheels will be turned to one side or the other when the steering wheel is on center, which will show up as an inaccurate individual toe setting. If the shop only checked it for total toe, which is the only adjustment, individual toe will not show up. With the truck being lowered, that can cause issues with the stock style drag link, possibly causing an incorrect Steer Ahead setting. You might take a look in the Tech Tips section, I believe there is a tech article in there on how to make an adjustable drag link for the AD trucks.
