Went on a 4x4 front end rebuild rampage about a month ago. I replaced everything that involves steering...all linkage, rod ends, u joints, ball joints,pivot bushings as well as a steering box.

Even after an alignment, the truck has super twitchy steering. I can go to change lanes on the freeway and turn the wheel a little bit and then all of a sudden it pulls into the next lane. At high speeds it tends to float really bad. Sometimes going over bumps it will float too. The other night I had to slow down and get off the road because it felt so bad. I even took it back to the alignment shop and had them realign it...still feels bizare.

I'm trying to figure out why my truck is all over the road, even after I've replaced everything up front. Any ideas?

I appreciate any input!

 

I hate to say it, but get under the truck and check the frame around the steering box for cracks. Check the outer side of the frame as well where the bolts enter through the frame.

 

I thought the same...I actually scrubbed the front of the truck down to check the frame and cross members and everything checked out. The steering is super sensitive...but the front end floats at around 60-65. The only thing I can think of is the caster may have been set up wrong at the alignment place.

 

What exactly do you mean by "floats"? Does it follow ruts in the road, wonder ect? When turning, does it return to center? What kind of suspension do you have stock, lifted? Have you checked the steering rag joint?

 

The other questionis, did they do a full alignemnt or just a toe job, most "shops" these days won't do anything but toe on these trucks as it might be too hard for their parts changers to figure out.

 

^^ What Matt says.... ^^

I would take it to an alignment place that knows and perhaps specializes in trucks (even large ones), as the problem sounds alignment-related to me (assuming everything else checks out and was done properly).

Perhaps a 4x4 shop, but certainly not a run-of-the-mill Brakes Plus-type of place you take the Toyota Corolla DD...

 

The description sounds like the problem I had with my '58 F100. In that case the front springs had sagged a bit, and when I put the 312 and T85 w/OD in, it made it worse. I basically had almost no caster angle. I ended up putting a set of 1/2 length helper springs on the back side of the axle. Truck drove great after that.

Did the alignment shop give you a print out of the settings? There are three values, caster (the front to rear tilt of the steering axis), camber (the in and out tilt) and toe (difference front to rear of the wheels). Caster should be a positive figure, camber should be right around zero and toe should probably be 1/8" from what I remember.

The caster is what helps center the steering, the more caster the stronger the centering. BTW, on our twin I or Traction beam trucks, ride height affects the values, a good shop will have this information in their database. Your truck should have eccentric bushings on the upper ball joint for alignment, a good shop will have a stock of these.

 

When replacing the balljoints, did you read the numbers on the camber bushings and/or reinstall them the same as you removed them?

 

The steering returns about half way after a turn then I have to help it back. When I did the front end work, I marked where the bushings were at before taking stuff apart. The shop did a full alignment on it, I sat out side and watched the guy mess with the adjusters and then set toe. From all of the research I've done the past few days it sounds like some caster needs to be added. Most of the shops around here either have no idea how to work on these or won't even touch them.

What I mean about "floating" is at higher speeds it will go where it wants...I have to adjust the wheel all the time.

 

I forgot to add....truck has stock suspension and rag joint is new as well.

 

Sounds like not enough caster. The wheel should return fully to the straight position by itself after a turn, and it should do it quite enthusiastically. You definitely should not have to help it come back to center. I agree with other above - find a real alignment shop who knows this front end. It is not a "Mr Tire" alignment job.

 

The "floating" your talking about sounds like the toe is set wrong, but could also be caster. Slight toe in, approximately 1/4", is what keep the vehicle moving in a straight line. Caster is what causes the tires to want to return to the forward position, think about the wheels on a shopping cart. If you can, find someone that's been doing alignments for a lot of years. Over the 20 some odd years of owning and operating my own 18 wheelers I learned to trust the old guys with there string and measuring tape more than the young guy with his computer alignment machine. Alignment really isn't that hard to figure out once you understand it. Heck, I used to do all the alignments on my old Jeeps my self using just some chalk, a measuring tape and an angle finder.

 

I agree with BV and Matt on this. Recently spent several months trying to get a mercedes aligned. Different animal sure, but 3600lb gvw weight and pretty similar suspension setups.

I'd been to 4 local suspension places, and the final one let me watch. Some goob through it on the computer rack, dialed the tie rods, called it a day. He'd missed 7 other adjustment points on the front susp. No idea what they were.

Finally through word of mouth I found a guy that runs a shop behind his 90yo mother's house. Did the whole thing by had with wooden jigs. Took him nearly 5 hours with a couple test rides thrown in, but it handled like a go kart after that. Interestingly enough, most of what was outside his shop was older Ford metal.

The other thing that came to mind is I don't see shocks and springs on your list. While all of this was going on my shocks and springs were shot. I could almost kiss the tire by doing a handstand on the fender, and I could compress the old shocks by hand when I got them off. How old are yours? What does the tread wear on your front tires, especially the left, look like?

With a suspension that's sagging under load your measurements are basically maxed out, if they even can be dialed in, and so any speed, wind resistance, bumps, tram lines, yadda yadda will put you right back at square one momentarily.

 

One thing to check also; Make sure the steering box is centered. After doing all that work, the splines on the input shaft of the steering box could have been off a tooth or so, or if you or someone else had the steering wheel off, it could have been installed back a tooth or so off.

Then you take it in the alignment shop and what does he do? He straightens the steering wheel till it's level, and then turns both tie rod ends till the wheels point forward. What does this do? If offsets the steering box when you are going straight down the road, and the steering box is made to be tighter in the center than on either side. If it gets out of center, the steering is sloppy, and you will feel the steering pass through the tight spot when turning one direction or the other.

 

Dave, what kind of Mercedes? I used to work for Tysinger in Hampton. The only guy I ever found who could align a king pin Ford correctly, was Stiltner Auto in Gloucester County. He did my 77 and my 86. The 77 when my oldest son got it, he had to put tires on it about 6 mos later. The place that put the tires on wanted to know who had aligned, said they had never seen a Ford truck wear the tires that evenly.