Thats the trick no one has figured out yet. You can hunt for a shorter or longer pitman arm, which raises or lowers the back of the drag link, or you can bend the steering arm at the axle end of the drag link. If yours is like mine, the drag link barely clears the top of the axle in stock location, so bending it down doesn't get you very much. On top of that, if you do change the pitman arm, you change the steering effort since the leverage has now changed.
Best bet is to add enough caster to hold it down, but not so much you can't parallel park it. My truck is lower in front, and the drag link is not perfect, but it drives as good as anything on the road. I can drive 65 - 70 mph all day without fear of bumps in the road. Good radial tires, are a must have. With the axle bump stops and frame location, I can't imagine the drag link being to far off, there just isn't enough room with a stock axle. Now if you have a dropped axle, then all bets are off.
Some people raise the steering gear on the frame to try to compensate for the lowering. The best advice is what the doctor gave to the woman who had an ugly baby- - - -"You grew it, so you need to learn to love it!" LOL! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. Ernest Hemingway
Here is a picture of my 4” dropped axle from Sid. It is level. I have 3” drop blocks in the rear. The change required a 3 degree shim and minor adjustment to the draglink.
Last edited by ndkid275; Sat Dec 01 2018 05:30 PM.
Over the past 45 years I've always owned at least one AD truck and during that time I've seen scads of them that others have owned and worked on some of those. It has always been interesting to me that I've never seen a single one with stock suspension and steering that had a drag link parallel to the ground. Not even one. Also I've noticed there are images right here on the Stovebolt forum showing 100% stock suspensions with their drag links also leaning that typical 15 to 18% downward angle (using the steering arm as the center point, parallel as one radius and the drag link as the other radius). If anyone has a bona fide image or picture of an AD truck with stock suspension and steering (and with good original type springs...not old wallowed out sagging springs or himmy-jimmy lowered springs) with a parallel drag link, I'd be very interested in seeing it. Likewise if anyone can point me to a passage in the AD shop manual with wording saying "make certain your drag link is parallel to the ground or shop floor" please do so. I've read the thing many times and evidently I missed that wording.
One could lengthen the pitman arm about 2.5 inches to take care of the problem, but I wouldn't. I saw this done in the late 1960s on a Ford in an attempt to correct the same situation (caused by a guy who wanted it to sit up higher). The drag link was then parallel but the leverage changed enough to make the vehicle dangerous. As you'd expect, the wheels turned quicker and it was harder to turn them...scary, actually. As I see it, the only safe way to adjust the drag link is by bending the steering arm or somehow raising the height of the place where the drag link sits, but I'd suggest doing this cold and bending it won't necessarily be easy. Jerry would be able to tell you how to do it using heat and I'm certain he has ideas/knowledge on this whole subject.
Here is a picture of my 4” dropped axle from Sid. It is level. I have 3” drop blocks in the rear. The change required a 3 degree shim and minor adjustment to the draglink.
Thanks! That's exactly my point. You've lowered the axle 4 inches and you've mounted the drag link upside down (on the bottom of the steering arm) to get it level meaning you have it a net 2.5~2.75 inches or so higher than where it sat when the truck was in stock condition.
No matter how simple or complex a steering system happens to be, it's all just a series of right triangles. The one we're dealing with in reference to the drag link/Pitman arm/steering knuckle setup is no different. If the drag link is angled up or down, as the axle moves through its range of motion in jounce (spring compressed) and rebound (spring relaxed) the length of the long side of the triangle (hypotenuse) is going to change. If the drag link starts out level, the change is minimized through the full range of travel and the bump steer will be minimal. Once any measurement in the geometry of the triangle changes, something else must be done to compensate for the error. The simplest approach is to alter the height of the Pitman arm pivot by relocating the steering gear vertically, but it's also the most difficult to deal with because it will change the height of the steering column. Putting universal joints in the steering wheel shaft would be an obvious way to compensate for that if the resulting angles induced into the steering column aren't excessive. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. Ernest Hemingway
Jon, the factory manual won't make any reference to the drag link being level because the suspension system in its "as manufactured" condition has that relationship built in. If the drag link isn't level, something is wrong with the springs, shackles, steering knuckle, or other parts that affect ride height. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. Ernest Hemingway
