Wanted to post something that I was recently made aware of.. I have read over and over again that the only difference between an early 1999 front suspension and newer trucks is the u bolts but that is simply not true. The early 1999 leaf springs have a gap between the two leaves at the eye because the spring is wrapped from the center of the eye instead of from the bottom. Therefore the springs rubs more on the bottom spring at the eye and the spring actually seems to have less stability.



A friend of mine has an '01 and he does crazy off roading so he took off his sway bar and track bar which I know can cause bump steer and body roll but with stiff springs it doesn't seem to be a problem. However, when I took off my track bar and went for a ride I hit a bump going about 35-40 mph and went into a horrible death wobble...

I think all my front suspension components are tight. I know these trucks are known for death wobble because they do not have enough caster. I'm thinking that the only think different between my truck and my friends is the early 1999 leaf springs must be more unstable and allowed the axle to shift more causing major bump steer that send my truck into a death wobble.

What do y'all think?

 

I have a late '99, the springs have the same gap. Are they weaker? who knows, but driving around with no track bar is going to be a far bigger issue than any difference in the springs. What's the point?

 

A friend of mine has an '01 and he does crazy off roading so he took off his sway bar and track bar which I know can cause bump steer and body roll but with stiff springs it doesn't seem to be a problem. However, when I took off my track bar and went for a ride I hit a bump going about 35-40 mph and went into a horrible death wobble...

I think all my front suspension components are tight. I know these trucks are known for death wobble because they do not have enough caster. I'm thinking that the only think different between my truck and my friends is the early 1999 leaf springs must be more unstable and allowed the axle to shift more causing major bump steer that send my truck into a death wobble.

What do y'all think?[/QUOTE]

How did you keep the axle centered when turning without the track bar? Seems to me the axle would slide all over the place.

 

The track bar is typically for coil spring suspension that can not stabilize the truck from side to side. Leaf springs self center the axle and don't need a track bar. The only purpose of the track bar is to reduce the bump steer but at the same time you are also putting unnecessary stress on your leafsprings and causing a stiffer ride and less articulation off-road.

 

When I lifted my early '99, I had to turn the steering wheel to line up my track bar after I lifted it and installed the new drop bracket. The front end of the truck would move three inches either way. I think that may have put more stress on the springs than a track bar (panhard) holding the axle straight while I'm driving in a straight line down the freeway. But that is just me. I do have a couple of buddies who don't run them on their trail rigs, but the also don't run their rigs on the street either. I'm on my third SD and I haven't experienced death wobble yet, I guess I'm lucky.

 

Wow that is a lot of movement... I didn't think leaf springs would ever allow that much... did you have aftermarket lift springs on it or were they the stick e99 springs with a shackle lift it something??

 

It was a Procomp 4" spring.

 

First your right on the spring design, the early 99 have that funky gap on the rear for some reason along with different bolts and smaller bolts on the track bar. Second the 99-04 suoer duty trucks do not expirence "death wobble" the 05 to 10 model trucks have this problem. And yes leaf springs do hold the axle in place but these are not medium duty or heavy duty trucks and the spring Eye rubber isn't designed to handle the side to side stress from the steering box SO PUT YOUR TRACK BAR BACK ON, and the track br does not limited the axle movement on these trucks the sway bar does and only the sway bar. I removed my sway bar from my f350 almost six years ago and haven't had a bad side effect from it. My front axle does flex like crazy now when I'm hunting or going dirt biking

 

I slapped it back on the other night and no more death wobble so it was definitely the issue! I wonder why the bushings in the rear are sufficient without a trace bar but not the front. I know there is less stress on them but what about when you have a big trailer? Seems like the axle in the rear would move all over the place also..

Mine is a little too mushy with my stock T code springs without the sway bar but when I soon get the X codes (I think) it should be stable enough that I don't need it.

 

Think about where the torsion points on the springs are when turning. (It's the eyelets and bushings). Using your logic, please explain how x code springs are going to change that. What are you trying to gain by removing the track bar? If it is travel, do what SDScaler said and pUllman your sway bar. I assume you see that this is ok on that pirate site. You should really take a lot of that nonsense with a grain of salt.

 

I was talking about the X codes helping me to not need a sway bar because they wouldn't allow as much body roll.

It wasnt on pirate that I found this out about the idea of ditching the track bar. It was from my friend who hasn't had onefor I think well over 100,000 miles and does insane off roading in South America as well as drives it back to the US with no issues. He hasn't had an issue with not having the track bar. His track bar actually completely shattered the frame mount bracket and that is why he originally took it off. It makes sense that the track bar would cause an extreme amount of binding when the suspension is articulating because it counteracts the way the springs naturally want to compress up and down not side to side. If there was an issue to be had with him missing the track bar he would of had it because he has every other issue possible. The guy is insane with his truck breaks leaf springs all the time, cracks and rewelds the frame. Has like 3 extra cross members. Blew up the Dana 50 and swapped in a Dana 60. Etc etc... that's why this is all a mystery to me why when I took mine off I had immediate issues but he never has. The only thing he suffers from is very slight bump steer as you would expect just as the old Chevy's had that also didn't have track bars stock. The reasons I mentioned the leaf springs being the cause is because that is the only real difference between our trucks. He has stock V codes with a tapered add a leaf. He has broke the add a leaf many times so you know he is putting tons of stress on the springs.

Heavier leaf springs would only help if the side to side movement is coming from flex in the leaf springs in which case a heavier leaf spring would have less flex. however, if the shift was from the bushings than no, heavier leafs wouldn't help. but as the guy said above, he had 3" side to side movement in his axle when he turned the wheel without a track bar. this amount of play couldnt be coming solely from the bushings because they dont have that much play to give. I am not trying to say my opinions are correct cause obviously there is something that I am missing. I am an engineering student and I enjoy the mystery and trying to figure it out.
Thanks for the help!

 

I am the guy that was talking about the side to side movement, the lack of the track bar with the increased arc of the spring allowed for the movement, and I guarantee you they were stiffer than x codes. I'm also a second year mechanical engineering student. With that said, you aren't using any sort of problem solving analysis, you are comparing the functionality of a highly modified truck(based on all of the repairs your buddy has made) with what I assume is a completely stock truck. Think about geometry and physics. Then think about the forces applied to the steering knuckles by the articulating drag link to change the vehicles direction as the vehicle moves forward. Inertia is going to try and push the chasis out over the wheels that are forcing the change of direction. You are stating that the four eyelets, plus the rigidity of the (two) springs is designed to withstand that force. What you fail to recognize, or less offensively, are not stating is that springs are rated for vertical forces and not side to side motion. The older trucks have up to 10 leafs in their spring packs and that is what helps compensate for bump steer and wandering, but not much. My old 85 F250 with a D60 conversion and a 8 inch lift drove like crap. It took everything I had to keep it in the lane, and going over 60 was a stupid idea. A track bar would have helped.
Now on the other hand, if you are looking to build a trail ready truck and get an extra couple inches of articulation out of your stock springs. Then you would have an argument to try and justify removing your track bar, but you will be back asking why your springs keep breaking (like your buddy's truck) and probably get answers like; "Why are you out trying to baja a Super Duty?". Just some things to think about. I'm not here to knock you, but I do think you are looking at the problem incorrectly.

 

I apologize it has taken me so long to reply. If you see the above text you will see where I stated that the only difference between my front end and my friends front end is the leaf springs. His truck is highly modified but his front end is not. Also referring to his leaf springs that keep breaking it has nothing to do with the track bar or stock springs. Actually the only springs that truly last him are his stock springs. The front "tapered add-a-leaf" on his truck breaks because it has more arch and ends up supporting almost all of the weight of the front end solely on the add-a-leaf. He designed it to be this way because he wants to keep his stock main leafs in the front because they are the best quality leafs you can buy and aftermarket ones break very easily. If his add a leaf breaks he isn't stranded, but if his stock main leaves break he is stranded. He has never broken his stock front leaves, just the aftermarket ones. I was mainly referring to him breaking leaves in the rear end and that is because of the crazy articulating he does with huge amounts of weight loaded in the bed and on his roof rack.


Here you can see the size of his leaf pack. Its ridiculous. And he loads his truck enough to break this leaf pack...
You mentioned the older trucks having up to 10 leafs, however, this is not true. The only old trucks that had a high number of leaves in their stock leaf pack were the really old ones, maybe early 60's and before (not sure on this), before truck manufactures started using tapered leafs. Ever since then the Ford F250 and Chevy K20 had 2 tapered leafs in front and Ford F350 and Chevy K30 had 3 tapered leafs up front.

This picture is from my buddy's 70's model F250.
If you lift a truck 8" without doing additional modifications to the stock suspension, yes, you are definitely going to have substantial drivability issues. But that does not relate to my situation just wanting to add heavier factory springs.
Looking at the geometry and physics you must realize that the forces on the steering knuckles and articulating drag link to change the vehicles direction while moving down the road are almost negligible. When you are moving at any substantial speed the highest force acting on these components is the force created by the caster of the front axle trying to push the wheels straightforward. The time that there is a lot of stress on the steering components are when turning at low speed or sitting still or offroading forcing your wheel to turn between rocks etc etc... As you mentioned the four eyelets and the rigidity of the front springs are what absorbs most of this force from turning. That the "springs are rated for vertical forces and not side to side motion" is actually what I stated in the above text. Leaf springs are not rated to absorb side to side motion, they are designed to prevent it and locate the axle under the truck. Looking at geometry and physics you will need to draw a force diagram and you will see that there is most definitely a force acting in the direction of the inertia of the vehicle, as well as a moment that is created by the weight of the body of the truck in relation to the ground, but in a vehicle you never go from steering straight directly into a sharp turn, but instead you will gradually turn the wheel. This causes a gradual transfer of this force onto the suspension parts and there is definitely a good amount of stress but I don't think that it is as great as what you may think.
The "10 leafs" on older trucks which I am assuming would only be lift springs or something of that nature would not actually help with the bump steer or wandering as opposed to just a couple tapered leafs. Multiple leaf non-tapered packs are progressive in spring rate due to the varying sizes of leaves while the tapered leaves are progressive by the changing thickness of the leaf itself. Multiple non tapered leaf packs might be stiffer because it has interleaf friction which provides a dampening action. However it is not well controlled and results in stiction in the motion of the suspension. Tapered leafs are just as strong and are cheaper to manufacture, they are less noisy, and often times produce a more comfortable ride. If you doubt the strength of tapered leafs as opposed to thick packs of leafs just look at the front suspension of most semi trucks that are suspended with two or sometimes even one thick tapered leaf (with no track bar).
On lift springs that are longer with more arc you are going to have more issues than stock springs because the small amount of movement in the bushings will be exaggerated by the longer leafs. A small amount of movement close to the axis becomes progressively larger as you move farther out. Also think about a vehicle sitting still, as yours was, when you turn the wheels and the caster pushes the axle to the side. You must realize that the movement in the bushings must be "allowed" by the leaf springs because, when sitting level, for the axle to shift 3" it requires twisting in the bushings as well as twisting in the leaf springs because of the leaf being held flat to the axle while the bushings are trying to rotate it sideways. This brings me to my point of how "thicker" or "heavier" leave springs would allow lest twisting and less body roll.
I am not trying to Baja my Super Duty... I have a ranch in Texas and will be doing slow moving rock crawling on rough trails hauling water trailers of miscellaneous equiptment and occasionally encounter mud in wash outs etc. I can definitely agree that a Super Duty would not be a good option for Baja without high modifications but the Super Duties do exceptionally well for my definition of off roading.
I went and looked at my buddys truck (without a track bar) and watched as he turned the wheel from side to side to see how much the axle moves. There was definitely side to side motion, however, it was not extreme and not an issue. As was said above that the bushings are not made to take the stress of the small side to side movement I disagree. I think they are plenty strong because my friend has had his track bar off of the front for over 130,000 miles and has replaced the rear bushings very often as well as the shackle bushings on the front but has never replaced the front spring eye bushings. They are still stock and have held up well, even better than the others. The only reason he has had to replace the other bushings is because of the extreme weight and constant bumps that his truck deals with that ovals out the bushings up and down but still no problems side to side.
Now back to my argument in summary:
Jobs of leaf springs:
1. to locate the axle forwards and backwards.
2. to locate the axle from side to side.
3. to support the weight of the vehicle
4. Reduce/control axlewrap.
5. Distribute the load along the length of the frame.

When designing a leaf spring for a vehicle you have to keep all of these things in mind and realize that making the leaf springs extremely thick might be good for all of these jobs of the leaf spring but it does not give a good ride quality. Therefore, you have to find a good balance between these things while still giving a good ride quality. My argument is that the x code springs are plenty strong to do all of these jobs and a track bar is not necessary unless you just really don't like the idea of a small amount of shifting in the bushings and does not do enough offloading to care about the stress the track bar creates. However, if we are talking about lifting a vehicle 6++ inches above stock then these factors change and adjustments should be made.

Sorry for all the carrying on but I am trying to make sure I explain my thought process to prove that I am thinking it through.