I have a 2003 HD2500 CC 4x4 Dmax with 285/75/16's and I have tightened up the torsion bars enough to get about an inch of front lift. The truck doesn't sit level but it is about half way between there and stock. The truck was aligned immediately after the torsion bar adjustment. I replaced the oem shocks early on with Bilsteins.

Here is the issue- at 49k miles my left front hub went south. The bearing went out and there was tiny silver bearing shavings all over the inside of the assembly when the dealer replaced it. At 53k miles the right front failed. Then I developed a clunk noise and at 55k the dealer replaced the pittman arm and idler arm and the dealer showed me the parts, they were noticeably loose and worn.

The dealer is pointing at my "oversize" tires as the cause.

Is anyone else having these wear issues?

I get the clunk now at 19k with h2 tires. I wondered what it was. Heavy Duty my a**

The clunk is it while you are driving and @ 55-65MPH B/c I have that as well

With a "HD" that is supposed to have the beefier susp components I don't see how the 285's are causing a problem. Especially if you just use it as a daily driver. If you abuse it then maybe. I've been running the 285's for a year and 13K and I hope I don't see the problems you are having. Let us know if you get it pinpointed!

No abuse, almost 57k mostly highway miles. The clunk is at low speeds like moving in and out of parking spaces or up and down my driveway.

replaced all at 60k(pittman an tierods) ...........where you been trace .......hows the redhead http://www.dieselplace.com/forum/smileys/Approve.gif

sdaver


Hola mi amigo, que pasa? The 5' redhead is prettier than ever and just as mean. Long time no talk. So you had similar front end problems too eh?


Is this from tires? The wheel offset? WTF?

TraceF- long time no see man!


My truck clunks, although its worse when i'm going over bumps at an angle. i think its my leafs, but i'm starting to wonder if part of the noise is from the front end.. 38k miles.. waiting for a laundry list before i take it in....

Hello again DP- slow bumps and turns at an angle and I still get some clunk. It seems like they got part of the problem but not all. When you say the leafs, I know you mean the rear... my clunk seems like it is under the front. Maybe I need the tie rod ends too like mackin. I'm stumped.


I bought this truck thinking I could run it a few hundred thousand trouble free miles and I am real dissapointed to find out that I am going to be doing $1500 worth of front end work every 50-60k miles.


Is there a "for sale" forum?

Hey ........... I don't need no stinkin tierods .... http://www.dieselplace.com/forum/smileys/Ermm.gif





Has anyone considered steering box "Clunk" ..... There is ample info on this problem out there ...





Waaaaaz up T ....


Mac http://www.dieselplace.com/forum/smileys/Geek.gif

I get a clunk every now and then too under the same conditions descibed above. I've read about the steering box clunk but I cannot determine if this is it. I'll be going to the dealer at some point in the near future to get this looked into. I'm running stock tires.

I don't think the oversized tires CAUSE accelerated front end wear, but if I hadn't put the H2's on mine, I might not have found out how bad the parts were already worn.


Apparently I had gotten used to hearding the truck down the road for 71,000 miles and didn't realize the inner tie rods had developed a half inch of slop - each! After I put the big tires on, I took it in for an alognment. Naturally the tech did a check for worn parts first and showed me how far each tire could be moved before the steering box moved - scary! I might not have ever gotten the alignment checked were it not for the tire swap. Dealer lube n oil changes for the first 50,000 miles, after that I did my own - and hit all 11 zerts, just never thought to wiggle the parts I was greasing.


Bottom line, my front end was maintained per the recommended lube schedule and had the stock tires - parts wore out anyway...


I thought I read that the front wheel bearings in the 4x4 are permenantly lubricated - maintenance free - from the factory, can someone confirm this?

Dave- you are right, the front hub bearings are internally lubricated. Don't know why the wore so rapidly. As for the steering box clunk, I haven't heard of this before but I have been away from the forums for a good while. Anyone refer me to a link?

Sorry Mackin- meant sdaver... http://www.dieselplace.com/forum/smileys/Geek.gif


Sure yours aren't worn too? I was like Dave Ski, I didn't realize how much I was working the truck to keep it going straight!

55K and I have replaced both wheel bearings, rotor was bent from the second bearing gone bad, two pitman arms and one idler arm and two tirods.

4wd launches and big tires ended mine prematurely........so I thought.......mac you owe me $5 for tacef's complimenthttp://www.dieselplace.com/forum/smileys/HiHi.gif

I bought this truck thinking I could run it a few hundred thousand trouble free miles and I am real dissapointed to find out that I am going to be doing $1500 worth of front end work every 50-60k miles.





http://www.dieselplace.com/forum/smileys/Shocked.gif What?!?!?! I have not heard of this please elaborate.

Dave- you are right, the front hub bearings are internally lubricated. Don't know why the wore so rapidly. As for the steering box clunk, I haven't heard of this before but I have been away from the forums for a good while. Anyone refer me to a link?


http://dieselplace.com/forum/forum_posts.asp?TID=532&PN=1





Dave the check is in the mail ....


Mac

It ain't nuthin new guys. I had my idler and pitman arm go out at 50k on my '98 GMC Z71. I had 285's and the bars were only cranked three turns. The replacement parts were still good at 160k when I got rid of it. Just plain cheap GM parts. I do remember swearing alot replacing that pitman!

Mac, Dave,


you guys all look the same to me...


Thanks for the steering box link but mine is more of a thud clunk than a rattle clunk. It sounds like something is loose under there.

Curious to know what actually happens to these idler, pitman, tie rod ends that define them as bad? What is the symptoms of these components going bad? Moog make any replacement parts for this stuff? Is this a weekend warrior task to R&R?

There are non replaceable ball joints that pivot when the components Move from one side to the other. Yes, it can be done in the driveway but it would be a lot easier with a lift and you will need alignment immediately.


Frankly I think part of my wear could have been caused by not lubricating the components often or well enough. I do my own oil changes and I moved in November. I have a detatched garage being built beside the new house and my compressor and grease gun are packed away at a mini-stor. I've been doing the LOF and little else for the past 20k miles.http://www.dieselplace.com/forum/smileys/Embarrased.gif

I am also having the clunk going over the speed bumps.....I only have 4,500mileshttp://www.dieselplace.com/forum/smileys/Cry.gifhttp://www.dieselplace.com/forum/smileys/Cry.gif

My '04 with 2,600 miles seems to have alittle looseness in the front end also--maybe from reading all these posts. This site is making me wish I never bought one of these damn things--I never visited any sites for info on my old gasser and she ran fine for 160k. Damn internet! LOL!

Had a the steering rattle fixed under TSB. Dealer greased the intermediate steering shaft and so far the low speed parking lot rattle is gone. Running 265's and the stock shocks are not handling the extra weight as well as stock. Bilsteins coming soon

One of the reasons I traded in my Durango and bought this truck was due to ball joint issues. I was hoping never to hear of "clunk issues" again but the sounds people here are describing sound very similar to the ball joints going bad on Durangos and Dakotas.


I haven't checked yet, are the GM upper and lower ball joints greaseable?

Wanna hear something funny? I THOUGHT I had the steering box rattle, even described the noise to a stealer and he confirmed, said the fix would take a couple hours and cost $60, truck is long outta warranty. I knew about the grease kit offered for around $10, so told him I would pass. So I rattled on for another couple thousand miles, THEN, I replaced the inner tie rod ends.


Rattle is gone, and I didn't touch anything other than the tie rods.


So this gets me to wondering. Does the average stealer squirt grease into the intermediate shaft, then do a courtesy lube of the front end while he's got your truck? If so, maybe packing grease into the inner rod ends quiets the noise for a while. I know several that had just the shaft lube comment that the rattle returned in a few thousand miles.


Another thing, I had to pump a LOT of grease into the fitting to get the rubber boot on the inner tie rods to be packed with grease, I think 60 pumps before I lost count. I figure the typical grease monkey will just hit every zerk fitting a couple pumps and call it good enuf when doing a lube job. That might partly explain the premature wear.


At any rate, I threw a tape measure across the wheels to set the toe-in at 1/8", that's just so I know I'm not loading the front end with too much toe-in and stopping the rattle that way, until I can find somebody with a Bear alignment rack in this area. Truck drives much better now, and a lot quieter. Total parts cost less than $80 (too much but I was in a hurry and couldn't wait for mail order) and took less than an hour in the driveway, or 3 beers for those that count in redneck time!


My advice, Check Your Inner Tie Rod Ends! Jack up one wheel and try to turn it back and forth.

I had the intermediate shaft clunk/rattle fixed 2500 mi ago,& is starting to clunk again. 20,000 on truck w/285-16 tires.Dealer thinks it may be steering box now.If its the box don't know why it went away for 2500mi. after last fix.

My old 01 2500 Suburban had the tie rods, ball joints, pitman arm and center links replaced at 40,000 miles; $1100 worth of warranty work that was covered by my aftermarket warranty AFTER I put my factory rims and stock tires back on and a very, very friendly inspector left me put my factory rims and tires back on for him to see instead of the Ultra wheels (which are only 16" with 245 Michelins on them) but they have 3/4" more offset to the outside and he said that would do the damage!!! He was a retired GM mechanic that now traveled to different shops to approve the warranty work and turned out to be very nice (he even liked the wheels). Oh well, sold the Suburban but kept the wheels and they are now on the 2500HD D/A!! Guess some people will never learn. Here we go again with the front end work!http://www.dieselplace.com/forum/smileys/Angry.gif

How many of these clunks you are hearing are the shocks and not the steering or ball joints?


Some of what is being discribed here sounds like it could be worn shocks. That is the first place I would be looking.


Just a thought here!

New bilstien's on mine & still getting clunk back.

Bilstein's on mine too.





Jacked the truck up Sunday to inspect and everything seems tight. I am going back to the dealer (different one) next week for another opinion.

Another thing, I had to pump a LOT of grease into the fitting to get the rubber boot on the inner tie rods to be packed with grease, I think 60 pumps before I lost count.
Holy crap! 60 pumps?? Man, I've never done more then 5 or 6 to any zerk in all my life.

I did my first lube at 850 miles, just because the factory seems to short on fluids, so I pumped the 11 zerks up front. Yes, the inner tie rods took alteast 5-6 more pumps than the rest, and they still did not look full, but I did not want to over pump them! I figure if I lube at every oil change eventually they will be full!

Oh yea, my front end now at 3,200 miles really doesn't "clunk" but does seem alittle "loose" compared to my old '98 Z71. Maybe a "rattle" but not really a "clunk". Overall love the truck, but in no way does it ride/handle as good as my '98 did. Guess a 2500 will do this!

Jim,


Neither did I before this. But I wasn't about to invest time, money and effort into a repair and have it immediately start to wear out! 5 pumps, absolutely no difference in the feel of the boot. 10 more, still just starting to feel a little goo in there. 10 more and starting to balloon a little. couple more just for good measure and noticed a little grease escaping around the big end of the boot on one side. So maybe 50 total for both sides. I was going to pump grease in there until I was SURE the sliding surfaces were well coated. The old ones, while greasy, are so worn I can push them to one side, let it go and the boot will snap it straight with no resistance, and I can push-pull a noticible 1/4 inch of play in the socket. Obviously never properly lubricated early in it's life.


Grease is cheap.


When I looked at the cross link before installing the new ends, there was almost no grease in the hole, and I had just hit it with 5 pumps on the same grease gun a few weeks earlier. Maybe the new ends were dry, or my old grease gun has a small pump, but I'm not gonna bother counting strokes in the future. They shouldn't need any more for quite a while!

Interesting thread... I have right at 10K miles on my 2004 HD, and I've noticed an infrequent 'clunk' under the driver's side of the floor on rare occasions. Is this the same clunk that y'all are hearing?


I don't hear it often enough to get that excited about, but maybe I should be.


I'll keep a closer eye on it.

That's my clunk. Right under my feet.

Are you guys hearing t-bar noise perhaps? They have been known to make all kinds of noises.

Dave, you got me thinkin, I am going to pump those suckers full tonight!

Okay, just read the whole post and thought I would offer yet another opinion on this. First off, take a good look at a 2500HD's front suspension and the suspension on the H2.that's right same/same....now that we now the suspension can hold up to a 34.5" tire take a look at the differences..on the H2 the tires fit as the body of the truck was designed to hold them, and clear them with no t-bar cranking....on the HD we have to crank our bars in order to clear those tires and many have also trimmed some plastic(nada to do with the suspension) So theory is that the tbar crank is what is causing the premature wear on parts, not the oversized tires.


Now on to the "clunk" couple things that I would check....look at your clearance between the top of the torsion bar key and the crossmember in which it sits...if you are cranked the key can actually "top out" against the crossmember leading to the mysterious "clunk" under your feet. Another place to look is at the droop stop for the UCA, the good old general made them out of metal, when you crank the UCA moves closer to this stop....and you possibly may be hitting it and the "clunk/thud" is transfered down the t-bar to the crossmember mount and you are feeling it under your feet, but in all actuallity it is coming from the front end.


Just a couple thoughts.


8.1http://www.dieselplace.com/forum/smileys/Wacko.gif

8.1-





These are good ideas but... I cranked the torsion bars 55k miles ago at about 2 or 3k miles. The clunk started at about 52k miles. There is something loose or worn under there.

I used to be a front end Tech years ago. I check for front end component wear at every tire rotation. The only parts that look a little small are the tie rod ends. They will be the first to wear if you are launching or running dry roads in four wheel drive. My truck is a 4X4 and I use it on dirt roads quite a bit. At 45K everything is in good shape. I can jack up one wheel, push-pull the tire and convince you that the tie rods are worn out when they are absolutely fine. Occasionally a part will come from the factory bone dry. By the time of the first service it is shot. More parts wear out from external dirt and water getting in because some kid lubed them until grease came out the boots. Mine will not take over three/four pump stokes to fill at my 10K lube interval.


Offset wheels with taller tires will put more load on wheel bearing and hubs. Cranking the torsion bars up increases spring rate. Worn shocks will transmit the shock to the from end parts especially when they stroke out or bottom out. I had a front that seized in the middle of the stroke. It actually loosened one of my eccentric bolts to the point the upper "A" was clunking.


As for the clunk-thud when backing/turning at slow speed it is the result of too much clearance between the input shaft and bearing in the steering box. Some trucks had too much clearance in the bushing that the intermediate shaft goes through. Greasing is a temporary cure that does not fix the root cause. My 99 1500 had this problem. They greased it once before replacing the shaft assembly. Later! Frank

I'm not trying to be contentious, but cranking the t-bars doesn't really increase their spring rate, it just resets their "zero." Now adding a 200lb front bumper, like I have done, will increase the load on the t-bars.


I'd also bet no one with stock travel shocks is able to hit the top metal bump pad under the upper control arm. When I had stock height Bilsteins, at full droop the shocks bottomed out and the upper control arm was not contacting the bump pad. With my RS9000Xs and a 4" lift, my upper a-arm does contact the metal bump pad at full droop. To do that when driving would require a severe bounce.


As I posted earlier, shocks with so much travel that they will let upper a-arm touch the bump pad puts the CVs in a bind at full droop. This is bad. I found I need and 11/16" bump stop to remedy this, so I ordered a pair and will install them this weekend.Edited by: afp1

Because the suspension uses un-equal length "A" arms the rate is increased. Later! Frank

Okay, let's persue this a bit.


I say all the unequal length a-arms do is keep the tire in camber.


The t-bar goes into the lower a-arm very close to the pivot, just inside it. As such, the t-bar moves in a very small arc.


Starting with the truck is sitting on the lower bump stop and the t-bar completely unloaded. As we tighten the adjuster bolt on the t-bar key, the load on the t-bar is increased until the a-arm is lifted off the bump stop. As soon as the truck starts to lift, the load is set. As long as the truck keeps lifting, the load on the t-bar remains the same.


The only way to change the spring rate is to use a different t-bar. You can hsort of cange the effective rate by changing the location of the pivot point in the a-arm or changing the amount of wieght the t-bar supports.Edited by: afp1

As soon as the truck starts to lift, the load is set. As long as the truck keeps lifting, the load on the t-bar remains the same.


The only way to change the spring rate is to use a different t-bar. You can hsort of cange the effective rate by changing the location of the pivot point in the a-arm or changing the amount of wieght the t-bar supports.





NOWAKE, how about doing an experiment? More on that in a minute.


First, I would like to jump in here and suggest there is truth to both arguments, and it is a matter of perspective in my opinion. I've been doing a research project lately that has helped me understand spring rates and how they may contrast with "wheel" rate (corrected rate at the wheel accounting for leverage), by virtue of the changing leverage that various a-arm angles produce. Also, most springs, including torsion springs, experience increasing rate with deflection (or twist). I am sure the 'at rest' spring rate is the same for each vehicle, one for AFP1, but spring rate (restoring force measured in lbs/inch) is a fleeting number and changes the moment you breath on the truck, increasing with twist. If it didn't, the truck would destroy itself. Since the lifted vehicle will experience greater torsion twist upon compression to the stop (hopefully noone will argue with this), it WILL have greater spring rate at the stop than the unlifted vehicle, when also compressed to the stop. One for Frank.


If we can agree on this, then clearly the a-arm and all of it's connections see more stress. This is seen by looking at the static stresses of the arm in a free body diagram.


This guy has done a good job with defining the mechanical job of the a-arm, and torsion forces


http://www.cardomain.com/member_pages/view_page.pl?page_id=271895&page=6


An excellent way to reduce these added stresses would be to move the stop also, when lifting, retain the stock separation between arm and rubber. Folks who are lifting without doing this, or at least adding extra damping in the form of real shocks, are adding uncertain numbers to the linkages, bushings etc. I can't do the numbers, but it is possible they are significant, especially after these oem shocks crap out, which is quickly forthcoming after a 2" torsion lift. Even bilstein is having problems. Adding a quality shock that has better damping would keep these repeat stress extremes minimized, at least that makes sense to me. I'd do it when new, at least on the front, at the same time you grease up and check the differential. I'm not alone thinking that putting the same monroe $5 shock on a truck with 1000 lbs greater axle weight is just plain dumb and inneffective, nevermind potentially damaging.


Soap box: What I still don't understand is the function of the upper limit metal stop, makes no mechanical sense to me, OE shocks are designed as the limit, which also makes no sense to me, making it difficult to replace them, and making it difficult for bilstein to make a replacement that doesn't also self-destruct. They just won't take any chances changing a seemingly flawed GM design, too much liability. If there is a good reason for it, someone here should chime in. I'm no suspension expert, just an Engineer. (I don't work for GM, don't hurt me!) Unless someone can compel me not to, I'm using a 1" shock spacer (also preserves stock leverage arm after 2" lift) and a 3/8 button poly stop over the metal stop.


Bringing me back to the purpose of this thread, and one other possible explanation for a clunk, if it is occuring in primarily torsion lifted vehicles. If you are 2" or over, you may be metal on metal, inside the shock.&nbsp

"Also, most springs, including torsion springs, experience increasing rate with deflection (or twist)."


True, but we do not change the amount deflection simply by cranking on the adjusters. We move the adjusters, which turns the t-bar, which raises the nose of the truck. There is no more deflection in the t-bar, it is just "resting" at a different location.


It's like putting a spacer under a rear leaf spring. The spring is lifted, but it still has the same rate and load, it just starts off at a higher location.


"Since the lifted vehicle will experience greater torsion twist upon compression to the stop (hopefully noone will argue with this"


This misses the point. The suspension moving up and down is not the same as adjusting the t-bars. When you adjust the t-bars, the entire bar--both ends--is moved. When the suspension compressed, one part of the bar is stationary and the other moves, so the bar is twisted or deflected.


Even bilstein is having problems.


I am not trying to be contentious, but actual data backing up this statement would very very illuminating.


GM should have designed the upper stop to keep the suspension form drooping so far as to put the CVs in a bind. Binding the CVs and running that way will very likely tear them apart. It is also bad to use the shock as the travel limit, as you can pull apart a shock. The bottom line is GM did not design this vehicle to be a heavy duty off road rig--not that any diesel pick-up is. I too am adding bump stops on top of the metal pads, because with my 4" lift and RS9000X shocks, the suspension will go to full droop and bind the CVs.

Hello Blaine


I don't disagree with your torsion bar statements, so I don't know why you are repeating yourself. My post restates exactly what you are saying.


"I am sure the 'at rest' spring rate is the same for each vehicle"


What was confusing about this statement?


Plus I have added support to suggest why the additional deflection incurred in a torsion lift, will add stress to various suspension component in the absence of other corrective measures.


The bilstein "data" you asked for will never show up in black and white, as you well know. But if you want to corroberate my statement, you can call bilstein yourself, as I did. Best I can do.


"This misses the point."


I think you have missed the point. If there was something you did not understand, please ask for an alternate explanation. If you disagree with something, tell me, I could be wrong. But I'm not going to engage in defending myself, I don't need to be better, smarter , or right. This thread was started to help someone solve a problem, let's focus on that. Clunking.


In truth, I think I am on to something. If you (reading this) have a torsion lift and get clunking over speedbumps and driveway curbs, try my experiment.

masterp2,


The discussion you jumped into--at least until you edited you post and added that last bit of info (which is okay by me)--was not about clunks in the suspension, it was Frank and I discussing his statement "Cranking the torsion bars up increases spring rate." As I stated, I wished to explore this topic more. I find many folks have misconceptions about how the cranking the t-bars affect ride. However, I am always willing to hear different ideas, if they are well supported, on how this stuff works. I do not know it all...........


"I am sure the 'at rest' spring rate is the same for each vehicle" What was confusing about this statement?"


The statement is not necessarily confusing or inaccurate, but it can be a bit misleading. Let me explain. Not only is the "at rest" spring rate the same, the rate is the same as the t-bar deflects though the same range as it did stock. So until you exceed the stock twist amount of the t-bar, the ride is virtually unaffected.


From my actual experience, normal driving does not cause this increase in suspension travel--it takes a pretty heavy jounce to twist the t-bar that far--and it is only a momentary condition anyway. Perhaps a better way to say it would be: Cranking the t-bars does not significantly affect spring rate or ride quality. However, any suspension movement beyond the stock limits will increase the spring rate and will likely cause a rough ride.


"But I'm not going to engage in defending myself, I don't need to be better, smarter , or right."


Actually, you are defending yourself by that very statement--I know from personal experience. There is no need to be defensive here--at least with me, because I am not challenging your character or credibility. I am assuming you are an intelligent, competent individual--even if you are an engineerhttp://www.dieselplace.com/forum/smileys/Wink.gif.


I believe there is much value to challenging and discussing ideas in a civilized manner. Ideas are "fair game" for being attacked, people are not. I have been posting in Internet forums for a while now. Most things that are posted are intended with the best of intentions, but they are almost always taken in the worst possible light. If we keep that in mind things will go very smooth.


Blaine

I don't know, you are doing a lot of talking, and still noone is disagreeing with you... till now.


your statement:


"The statement is not necessarily confusing or inaccurate, but it can be a bit misleading. Let me explain. Not only is the "at rest" spring rate the same, the rate is the same as the t-bar deflects though the same range as it did stock. So until you exceed the stock twist amount of the t-bar, the ride is virtually unaffected."


is wrong, yup wrong. Especially that last sentence, a lulu.


Spring rate is irrelevant once you change the angle of the A-arm with reference to the force of gravity. And Blaine, that is what torqueing on the torsion bars does do, as you have pointed out. The spring rate is nothing more than force, which is meaningless without an arm to act upon, thus becoming torque. The torque required to oppose the vehicle weight is less, much less, in the raised vehicle. Lowering the a-arm effectively changes the leverage arm through which this same "spring rate" is acting (vertical direction opposing weight), in fact it lengthens it, effectively making the spring, well, LESS springy, but the wheel is still holding up the truck, through mechanics. Now comes the deflection, but the wheel has less torque behind it to resist motion, hence it is going to deflect further, accelerating faster toward the stop which, as things would have it, is further away. WOMP, rubber ride! Fix: relocate the stop.


The spring rate is the same, but SO WHAT? It is irrelevant to anything in this discussion titled "Front End Clunk..." http://www.dieselplace.com/forum/smileys/Wacko.gif That's the discussion I jumped into, which was in the process of being hijacked if anything.


Where ride comfort (and bushing longevity)is concerned , wheel rate is what matters. When things are wearing out, a-arm angle is where you look, lowering them increases self-destruction tendencies of anything that is attached to the arm, which experiences compression over every bump, turn, or braking. Not good.


There is no point in comparing before and after spring rates if you don't keep the a-arm angles constant. Apples and Oranges. The "stock twist" has nothing to do with reality. The only, ONLY thing stock twist is relevant in addressing is whether or not you may have a broken torsion bar after you lift the vehicle with it. If you don't relocate the stop, that is an uncertainty.


And BTW, I edited nothing after my post was responded to. I have no idea what your point is. How did I get sucked into this?


Yet again I'll ask, does anyone want to readdress the possiblity of clunking being in the shock? Blaine?

I gotta agree. There is a difference in "spring rate" and "effective spring rate". We see this all the time on offroad high travel suspensions where the changes can be rather dramatic in some setups. You are correct in that the actual spring rate of the torsion bar does not change when "cranking" the bars or changing keys. However, the "effective spring rate" (which is the important consideration here) does change because of the effect of the angled lever relative to the force applied (which could be shown with a force vector model). So, more or less, you’re both right on the base facts, but your talking different things, only one of which is relevant to the problem.

Masterp2,


Unfortunately, you have just shown yourself to be the kind of person I do not associate with. My apologies if I have offended you in any way. From now on, I will avoid interaction with you. Edited by: afp1

You gentlemen left me behind a long time ago but I can pick pieces out of this exchange that I can coment on that may make my particular situation a little clearer. Let me restate a few things.


First, the torsion bars were cranked at about 3k miles when I went to the 285's. The truck was aligned immediately. The clunk started after 50k. I have replaced both front hubs, the pittman arm and the idler arm.


The clunk started in the midst of these replacements which occurred between 49k and 54k miles.


I think I caused the accelerated wear at least in part. The truck has been in deep water a few times (hubs) and I change the oil in the driveway and haven't been dilligent about the lube grease.


I think the new tighter parts are putting stress on something else that is worn and resulting in my "clunk". But everything seems tight. Just a hunch.


My dealer is scratching his head too.

Please pick out the constructive pieces out of my posts. Everybody reporting a clunk on this thread has a torsion lifted the truck.


It may be a coincidence that your noise started after work was performed. These shocks take a real beating on torsion lifted vehicles, statement by bilstein. I came into this thread after 20 posts, the benefit of that is clearer perspective. 8.1 made a suggestion early on that made me think of this, except he remarked about noise being possible at the downward travel stop, which was quickly shuffled aside when it was pointed out that the shock is the downward limit.


We may never solve this problem, but can you isolate your shocks, either take them out and drive, or put a thick stop on your downward travel limiter (see suggested experiment). I just have a hunch, that you are the victim of a GM engineer. It may not work, but you can't complain about the cost. Free replacements!


BTW, the bilstein rep I spoke to said the "top out" caused failure may not be immediately apparent in ride, as it is the REBOUND side that loses damping first, when damaged in this way. That would let the shock top out even easier. Makes sense. No rebound damping=slapping at the top limit. The best part, is that this is not reproduceable on the lift. And since no other vehicles that I am aware of use the shock as the travel limit, dealers would never suspect the shock, as no doubt none of them understand the dynamic of this front end, nor do they typically get rid of noise by replacing shocks. The only way to tell is to get the shock off or isolate it. I have been longwinded on this, time for me to shut up.


What do you think?





Edited by: masterp2

Bad Dog,

Both you and Frank have mentioned how an the a-arms change the effective spring rate. I want to engage in a polite discussion on this issue. I want to explore your comment:

"However, the "effective spring rate" (which is the important consideration here) does change because of the effect of the angled lever relative to the force applied (which could be shown with a force vector model)."

What I am seeing is the t-bar is anchored in the same location in the crossmember, and it enters the lower a-arm in the same location. This is true regardless of where the t-bar is indexed. The portion of the t-bar entering the lower a-arm moves in a very small arc. The a-arm changes it's position when the adjusters are cranked--a slightly more downward angle away from the frame--but the arc does not change.

So the force that is applied by the t-bar is applied in the same arc, regardless of the adjuster position or angle of the lower-a-arm. If it it applied in the same arc, how can force be changed?

On my truck, I have the Realift t-bar relocators. I can see how these relocators could change the effective spring rate, because they do change the arc the t-bars operate in. However, after having a 2" t-bar lift, having a 4" Rancho lift without relocators, and a 4" Rancho lift with the relocators, I can say from personal experience the change in ride among all three situations here is minimal.

Here is a pic of the relocators. You can see how they change the arc of operation. First is a shot of my truck. The next shot is a shot of a different truck--it is a better view, but I can't speak to that truck's ride. Also, I have had two different sets of t-bar relocators, one that was indexed more than the other. There was no difference in ride.




<IMG onMouseOver="this.style.cursor='hand'" onMouseOut="this.style.cursor=''" alt='Click on image to open in new win

Are you familiar with force vectors as a tool to understand effects of non-perpendicular forces? If not, it’s going to be tough to explain. But the arc of the arm really has nothing to do with instantaneous (at any moment) effective spring rate.

Hmm, as a simplification, think of it like this. The force of gravity is pulling straight down on level ground. This means an equal force is pushing up on the tires, and the torsion bar is caught in the middle, deflecting to counter that force. But, it has leverage working against it in the form of the suspension arms. Longer leverage means the bar must absorb more forces. But, it’s not just the actual physical length of the bar. It’s (sorta, work with me here) really the distance from the pivot point *relative to the force applied*. If the lever (arm) is parallel to the ground, it is perpendicular to the force, and the simple level equations work just fine. However, if the arm is not parallel to the ground, then some of the force pushing up on the arm, is actually “redirected” horizontally toward the pivot, and the balance (not accounting for parasitic and other losses) goes into deflecting the arm/lever upwards.

Look at it this way, take the extreme case of a nearly vertical lever/arm and imagine a force pushing up on it at the end. This would give little leverage in applying the torsional force to the pivot, so you would probably just lift the truck without any movement of the torsion bar. Effectively a VERY high spring rate. Maximum leverage and minimal spring rate would occur with the lever/arm horizontal, and there would be a curve describing the transition rates between these two extremes. So, effective spring rate is always changing as the lever moves through it’s arc. If static height from the factory leaves the arm at a 20* angle, and you crank (or key, or whatever) to get a 25* angle on the arms to provide a higher static height, the actual spring rate does not change, and the effective spring rate *at that angle in the arc* does not change, but the effective spring rate at static height will be somewhat higher if no other efforts are made to compensate.

The relocaters confuse things still more by changing the lever arm as well. But being an effectively longer lever arm, they may well neutralize any increase in effective rate. BTW, the sha

Oops, just realized, that relocater moves the mounting point out away from the pivot point. That complicates things further since this is not just a simple lever (though it can sort of be treated as one when the torsion bar is at the pivot). Not sure exactly what the net change on that would be without doing more work than I'm interested in tonight...

Bad Dog,


Your explanation makes sense to me. It's the same sort of idea as lift vs thrust vectors in aerodynamics. If I understand you, the t-bar's effective spring rate would be increased (stiffened) as the angle is changed from pure horizontal.


I guess the issue is "how much change in rate?" From personal experience I know it is minimal, within certain limits. Perhaps the rough ride that happens as the t-bars are cranked can easily be overcome by the shocks up to about 2" of increase.


I have always wondered how effective my 1" spacer under my shocks was in terms of ride. Many guys with no spacer and 2" of lift felt they had a good ride. Now what a good ride is is subjective, but assuming we have a similar feel for ride...............


My spacer did keep the shock closer to center, but perhaps a bigger factor in ride was the shock's diminishing ability to dampen a progressively stiffer spring rate. Even with the 1" spacer, my truck's ride became exponentially rougher as I increased the t-bar lift over 2". Perhaps the 1" spacer did not help at all in terms of ride, because my experience mirrored guys running t-bar lift without spacers.


Now, I didn't initially think of running the spacer so much for ride as I did shock travel. I guess it worked, because I never did have any "clunk" with 2" of t-bar lift. Then again, I only put about 18,000 miles on the vehicle with the lifted t-bars, and I changed to Bilsteins at 6K into that 18. I didn't have the spacers until I installed the Bilsteins.


When I pulled off my stock shocks at around 11-12K, they were gone. They would hiss when compressed, and they compressed in a very jerky and uneven fashion. They would rapidly drop about an inch then stop, the jerk down again. However, even with the shocks worn out this way, and with no spacer, I didn't have any clunk.


Blaine

Sounds like you've got it down.

And the rate of change does vary with angle. The change per unit (degree) is smallest near horizontal, and the rate per unit increases as you get closer to vertical. In fact, if you eliminate all the noise of reality, the effective spring rate goes to infinity as the arm angle approaches vertical, with very rapid changes as you get closer to vertical.

Don't forget about rough ride possible cause #129:


When you deflect the arm down in the lift process, and go past horizontal, you create a "dipod". With the tires planted on the ground, arms at an angle, the greater the angle (from horizontal), the more the tires will resist the side slipping motion necessary to compress suspension=apparent addition to spring rate. The slower you are moving over a more paved surface=the greater this resistance. Higher speeds over dirt=less resistance. Just like the mechanics of doing a dancers split. Easier to split with legs far apart than only slightly spread. Easier in socks, than with shoes.


Also=tire wear. Not to mention, adding forces in the horizontal component, to everything connected to the wheel, inboard of the wheel itself.


Aside, will just politely suggest that this discussion should be used to start a new thread. Edited by: masterp2

masterp2


I am hearing you say (I think) that cranking up the torsion bars causes my Bilstein's to top out and consequently may have prematurely worn them out. This strikes me as a possibility, it seemed like they were shorter than the oem shocks when I put them on.


http://www.dieselplace.com/forum/smileys/Confused.gif

Like others, I am trying to put the common puzzle pieces together. I started thinking, dangerous I'm told. I'm trying not to be too emphatic as I'll just be embarrassed. Also likely is that there is more than one "clunk" noise. Some folks report the clunks still there after replacing shocks????? Perhaps those folks are indeed hearing the metal-metal suspension stop, which could happen if using longer than oe shocks. (back to the experiment I suggested). But yes, torsion lifting gets you closer to both, the stock stop and the suspension stop. And a fact, bilstein is recieving back top out failures. 2+2=?


If the noise is prevalent in torsioned trucks, then it should/may be related to the physical forces that may have changed at the suspension level.


The shocks came to mind, because topping out the shock is an inherent likelihood, more probable and frequent with torsion lift.


The other thing that came to mind while writing the last post, was the a-arm pivot connection, upper and lower. Are they bushings? If so, they'd be subject to quickly deteriorate under the added stresses induced in the dipod configuration. I'd look there for signs of play.Edited by: masterp2

Good post masterp2 especially the first one. I only cranked my truck up 1" with the torsion bar adjusters. I mainly wanted to bring the left up to match the right. I knew that camber &amp; toe in/out would be effected and the ride would suffer if I went to far. I noticed the clunk/thump at very slow speed while turning. Like I said: The new box cured the problem. Later! Frank http://www.dieselplace.com/forum/smileys/Big Smile.gif

Frank, I re-read all your posts, but I don't have a tech background, so not sure what you are saying.


If you induced a clunk by lifting, how does a solution other than "lowering" et al, solve your symptom? You are pointing to the steering box?


How about for the folks getting this noise straight ahead over speed bumps?

I mostly get the noise at slow speeds turning, it doesn't matter if I am pulling in the driveway or backing out. I notice it a lot in parking lots. It may well be there all the time, and just be easier to hear at very slow speeds.

trace. is it on the driveway bump? Turning does put one side up and one side down. Good point on the low speed, low noise correlation.


How about speed bumps, straight and level? Do you get the noise while going slow, staight ahead and reverse, be specific?Edited by: masterp2

Michael- there doesn't have to be a bump. It is just the movement of the truck and change of suspension direction or angle.


When you take a 7000 pound truck and move it things flex. I am gonna tie myself under it and let my wife go around the Piggly Wiggly lot.


I'll fing the noise http://www.dieselplace.com/forum/smileys/Cool.gif

LOL!http://www.dieselplace.com/forum/smileys/Clap.gif

Raising my front end had absolutely nothing to do with too much bearing to shaft clearance in the gear box. This is an old topic that has a fix. Check this TSB right here on the forum. Later! Frank


Noise from Steering at Low Speeds #PI00299 - (07/30/2002)


Edited by: Frank Blum

Frank- how do I link to a TSB?





Never mind, found the link http://www.dieselplace.com/forum/smileys/Geek.gifEdited by: TraceF