Hi all,

I am looking for some input on an issue I am having with my truck. Currently, the truck will only drive straight down the road if I hold constant pressure on the right side of the steering wheel cocking the wheel to about 10 degrees clockwise. If I let go of the steering wheel while driving 60 mph on a slightly crowned road, the wheel will turn by itself about 10 degrees to the left and the pull me up over the crown and into the other lane. Now, this does not happen instantly, and it depends on how smooth the road is, but it will start pulling within a few seconds at most. When I go around a sweeping gradual left turn on the interstate at 70 mph,(On my way home from work everyday) I can just let go of the wheel and it stays in place at about 10 degrees counter clockwise and just keeps me in the lane.

Now for some history. The truck has about 45,000 miles on it. Most of which have been empty using as a daily driver on paved roads. I would estimate only 6-8k miles have been towing, and that's been light trailers mostly, no over weight loads. I have been running 35" tires for around 30,000 miles. I ran Tread Wright Guard Dog 315/70-17's for a few years and most recently(a few weeks ago) had Cooper Discoverer STT 35x12.50-17's installed. Around 5,000 miles ago I was having bad tire wear up front and a bit of death wobble. I found a bad ball joint on the drag link. I replaced that and the death wobble was a bit better but the tires had worn so badly that they themselves wobbled. I rotated them to the back and it helped a bit more. I also replaced the front stabilizer with a Bilstein 5100. I ran the tires up until a few months ago and then had a new set of Guard Dogs installed and had an alignment done. It was done by a local shop here in the sticks and he did not use a computer. He did say that the alignment was out and he adjusted it in but didn't say what part was out. After the alignment I noticed the truck pulled left a bit more than before...or at least more than I remembered, but I do not drive this truck everyday. As I drove the truck over the next few days I noticed a VIOLENT shaking coming from the back of the truck. I took it to a different shop(also local, also low-tech) and he rebalanced the tires. Shaking was still there and just as bad. He said it was the tires for sure. I went through a big long drawn out fiasco with Tread Wright and long story short, they refused to do anything and I sold the tires off and bought Coopers. I took the truck to another shop. This time it was a national chain store and they had a real alignment rack and I ultimately bought tires and had them installed there. No more shaking after the new tires, but still pulled left. I asked them to do an alignment. This began a 3 week journey that led to today, where I finally get my truck back, two caster adjustment bushings and a bazillion hours on the alignment rack later.

When the truck was first on the rack, they brought me back to the shop and showed em the screen. The right caster was too negative, at about 1.4 degrees. The left caster was at 1.8 degrees. The camber and toe were about as good as they could get. The tech asked if the truck was pulling right, and I said no, it's pulling left. He was baffled, and I was too as the caster measurements indicate a likely pull to the right. The thrust angle was at 0.1 degrees, which technically would aim the front of the truck to the left, but the tech didn't think such a small angle would cause a pull like I was experiencing. They checked all of the front end components including the brakes and the bearings. Nothing seemed to be wrong. They suggested installing caster adjustment bushings and trying to align it again and see what happens. It took several attempts as we kept getting the wrong bushings but they finally got it aligned today. So after all that it still pulls left just the same as it did before. I will try to add the image here of my printout of the alignment. Let me know what you guys think.

I have read threads about certain tires causing the truck to pull to one side. Many have said Toyo M/T tires cause a pull to the right, and Nittos cause a pull to the left. No matter which way the swap and rotate tires around. On my truck, the tires have been swapped around, air pressures have been checked and changed. I am at a loss. I can deal with the way it drives, thought I won't like it. What I can not deal with is ruining a set of $1400 tires in no time because I am scrubbing the left side of the tread every single second I am driving just trying to hold the truck straight. If anyone has any ideas at all I am open to suggestions.

Thanks guys!

 

Hope everyone had a good new year's eve! No who's got ideas lol

 

It could be a steering box issue. I have had situations where a shop replaced a drag link, got the adjustment wrong and the steering box was not centered, and the steering box tried to center itself creating a pull to one side. It could be track bar adjusted wrong, or worn bushing if stock.

Brian

 

I was curious about the steering box...I wondered if it had any self centering function or if it relied on the toe of the tires to track straight. As far as worn bushing, are you referring to the track bar bushing? The mechanics said they checked that but that doesn't mean it's not an issue. Also, I never even looked but I thought the stock track bar was not adjustable?

 

I refrained from posting earlier because I'm certainly no alignment pro. But I can say that a worn drag link end will not cause funny tire wear because it doesn't affect wheel alignment whatsoever. It'll cause lots of steering slop and perhaps an off center wheel, but that's about it.

A bad steering gear(not a box) could cause your issue, but I would think you'd notice unequal steering assist during all conditions if that was the case.

 

Well the drag link caused a bad shimmy which caused the tire wear initially. I do not understand what you mean about steering gear vs steering box. I do not have unequal assist however. The truck loves to wander, the effort to turn the wheel is so low compared to any superduty I have ever driven. Even my wifes 2011 F150 is much firmer. In fact, I just got the same Cooper tires put on her truck a month ago and hers rides and tracks great still. You could practically take a nap on a flat straight road with her truck.

 

The comment on the steering gear is simply me being nitpicky about terminology, that's all. There's no such thing as a steering box; it's called a steering gear.

I noticed that my Excursion also had an easy wheel to turn, much more so than my F150 so I'd say that part is normal. The tendency to wander is almost always a symptom of too little caster, but of course yours is showing to be within spec. I'm not an alignment tech, and so I don't know how they measure caster but I'd guess that yours is incorrect. The truck should want to go straight down the road, not change direction without steering input.

 

IMO this is common in many Ford trucks. I replaced my OEM steering stabilizer with a duel unit for this reason.[https://imageshack.com/i/2hkrx3j

 

Did your truck pull or just wander before the dual stabilizer? Did the dual stabilizer correct the problem/s ?

 

My truck pulled right and wander slightly when new. I think the stock 34" tall 10" wide tires are large and going wider or taller causes handling issues. The duel stabilizer made my truck easier to drive straight at hwy speeds. (w/slight increase of steering wheel effort)

Has your truck always drove like this from day 1?

 

 

The steering stabilizer only exists to resist motion; it can't apply force to one side or another. It'll counteract bumpsteer and death wobble, but it should have little to do with wandering.

 

The duel stabilizer stiffens/tightens up the front suspension. It stopped my wandering nearly 100% on a new truck.

Swapping the rear tires left to right would be on my list.....a 1/4" taller tire can cause drifting issues.

 

I should have stated that better. My point was that a bad stabilizer can't cause the OP's truck to pull to the left because it's incapable of applying that kind of force.

 

Bump to the top...