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Hello All,
I am new to the forum and wanted to bounce around an idea with you.
The Truck: 2002 F150 FX4 5.4L with a Fabtech 6" lift and 35x12.50x17 tires.
The Failure(pics attached): The idler arm where it attaches to the frame mount (thinner metal boss welded to the frame) tore out. What I mean by that is that it ripped the metal of the frame mount out taking a chunk of the metal and the bolts still tightly in the backing nuts right out.
The repair: My frame and body guy hammered it all out welded the ripped out chunk with the nuts back into it's proper location with a huge set of welds and I had the front end aligned.
The question: Being that this happened minutes after I pulled off of an all day trip on the interstate I am now I bit gun shy about driving the truck and want to over-engineer the repair with some brackets. My thought is two "straps" of substantial steel (3/8" or thicker) that weld to the frame in front and back of the spot where the idler bolts on and pass over the idler arm with a hole in them through which the bolt will pass. The bolt then passes through the idler and finally back into the original mounting holes. My question is has anyone ever done or seen anything like this and does anyone have any better ideas to strengthen this area or is there an aftermarket kit of any kind to accomplish the same thing?
I am not sure that makes any sense but if you get what I am trying to say any advice is greatly appreciated. Thanks!
It was pretty scary to realize 10 minutes sooner and I would have been doing cartwheels down the highway tied to a boat and trailer. unnerving to say the least.
Keep an eye on it, its been working apart for a good while. I feel for you had all springs brake on me doing 60 MPH in a Semi. Locked both axles up went from the left lane to the shoulder and back across before getting it stopped. Made me start keeping an eye on stuff after that.
Pete
It's ironic that yesterday in another thread someone wrote that as long as your truck is level everything is fine with your torsion suspension, and then you post this.
A few years ago an engineering student, Cristina Jopa did a great research paper on steering and front suspensions in Formula A cars. "A" cars are research cars. Do an internet search and read it. A lot of math but she does a good job of explaining.
Also do a search on steering and torsion bar suspension failures that have to do with front end alignment.
If it isn't too late, have your mechanic check your alignment. Does or did putting your front end in alignment result in anything being out of spec? Particularly castor and toe-in? I don't know what the specs for the 150 are, but typically somewhere between 0 and +1 degree with an adjustment limit of around +4 degrees. In your searches, if you do them, you will find failures where alignments are maxed at the 4 degrees to get a front end aligned.
I've seen this failure of yours before but not with your history. Are you the only owner of the truck? Back in the early 80's I resigned from the service to go back to school and while waiting I took a job with an engineering firm that was modeling what's called the moments of inertia under different loading conditions. The reason for the modeling was because of steering and suspension failures that happened mostly because of plowing but there were other conditions also.
Anyway, examining your alignment is the place to start and don't ever buy into everything is OK if the truck sits level. It's just not that simple. It also doesn't mean something is wrong either. The steering and suspension are tied systems and when tracking a failure you have to start somewhere.
If you read Cristina's paper, pay attention to "bump steering." Not to be confused with bump stops of torsion suspensions. For more general information look up the failures in early Chrysler torsion suspensions when used with leaf springs in the rear, and Porsche's research and their use of torsion bars.
The bolt spacing? I was in a hurry last night and I'm just trying to figure that one out. Seems no one has an answer about why the 2 spacing's were used.
Thanks for the insight I will read up and educate myself.
To answer the questions, no I am not the original owner. I have been experiencing a wobble from the time I bought the truck. My theory is the previous owner wheeled with it maybe a bit too rough and came down on the passenger side hard. I am thinking that it has been cracked and failing as long as I have had it then just the constant pressure on it from the big tires (35x12.50x17) steering at slow speeds just kept flexing it back and forth like a beer tab until one day wham-o it finally snapped. I have had the alignment done and the front end inspected for other damage by a very reputable mechanic in town and he says it is all good.
I am still a little nervous not knowing for 100% certain that it was damaged when I bought it so I am in the process of fabricating a bracket/brace (piece of mind). My original idea of going over the whole idle arm and welding in front and back won't work. There is not enough clear open space to weld to the frame on the rear side so I came up with the bracket design attached below that will weld only in front and bolt using the original idle arm bolt locations. I am thinking if I use 3/8" steel to fab it I should be good. This should keep it from failing or being able to rock back and forth again causing the mount to stress. Worse case scenario if somehow the original mount breaks in the same manner this will keep the idler arm basically held in place allowing a safe pull over and stop instead of a cart wheel down the highway.
Thoughts? Is my thinking logical on this or is there anything I am not considering?
07-29-2015, 04:41 PM
Idler Arm Catostrophic Failure
