Will Somebody PLEASE Buy Mexico another Torque Wrench! A Death Wobble Discovery.

[DIESELMAN]

This is long, but, Gosh Darn it all to Heck, and all those other words that come with bloody knuckles, auto parts receipts and very simple discoveries.



My truck with roughly 40K has been slowly exhibiting more and more Death Wobble. I have examined the drag link play in the rubber bushings, 0. 030", I have checked for Ball joint looseness, I have checked for anything that might be loose in tolerance and causing a shimmy that builds to a Death Wobble on the freeway.



I have replaced my shocks with Rancho RS9000's set on 9, I have replaced the steering stabilizer with an RS5000 unit.



These things are not it, but they look good. Real Good.



I did add 315's and nearly wore them out before this has begun, I've been to Alaska and Back, twice. I've lifted it 2" with a leveling bushing from Daystar, and my lazy a$$ dealer tech says, " welp, deres yer problem see?". Thats BS.



I've rotated my tires and always balanced them on the slightest bit of tire thumping or inbalance, and this ain't it.



I took it to the dealer again who said, well, the front end alignment is "IN SPEC", Thats BS, I think they don't know how to measure it correctly.



So, I built a jig to measure Caster myself, and every time I thought I had it correct it told me about 0. 5 degrees positive, can't be, thats wrong. No it was right.



I then set out to do something that is much simpler than I thought it would be. I put a tourque wrench, 15/16" on the Cam nut because I have a nice long handle on it, and set out to break the 160 ft lbs that the lower cams should be tightened to, and it nearly broke my knuckles open when they slammed into the concrete.



Checked the other, and it released at 20 POUNDS!, in fact the adjuster turned as soon as I put pressure on it.



Seems someone in Mexico got confused. What I found, though I have not confirmed this on another truck, is that with the adjuster bolt at the bottom, indicator straight up, the angle is near 0 caster, I moved it forward 3. 5 notches which now indicates about 4. 5 degrees on my gadget, and the truck runs like new, straight and true, no pull and.....



No Shimmy, no excitement, no Death Wobble.



It appears to me that either the bolts were not torqued properly, that is to 160 ft lbs, or they work themselves loose, and that the nuetral or settled position of the weighty beast sets itself to almost no caster, and sets the condition for a Death Wobble. It also appears that the notches are about 1 degree each.



What really irks me is my dealer tech and his "looks good to me, duhh".



Now, I need some confirmation... ... anyone?

 

[HEMI®Dart]

Good Find Dieselman! Hopefully clwilliams will see this thread and check his cam adjusters.

 

[Gary - K7GLD]

That adjusting caster affects some rather nasty steering effects is no real secret - the TRICK, is finding that magic adjustmet that minimizes problems while still allowing maximum tire life - sometimes what you SAVE on one end, you PAY FOR on the other!



Get back to us in 20,000 miles or so...

 

[rbattelle]

Wow, outstanding work Dieselman. I am particularly impressed that your built your own caster jig! Can you post a couple pics of the jig, and how it's made?



Just goes to show you, the simplest answer is usually correct!

 

[HEMI®Dart]

Originally posted by Gary - KJ6Q

That adjusting caster affects some rather nasty steering effects is no real secret - the TRICK, is finding that magic adjustmet that minimizes problems while still allowing maximum tire life - sometimes what you SAVE on one end, you PAY FOR on the other! Get back to us in 20,000 miles or so...

I run as much positive caster as can be dialed into the axle and my tires are about 6 or 7 years old. Have about 70K miles on them. No funny wear patterns and decent tread left



I'll bet Dieselman has an Angle finder.



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[DIESELMAN]

Originally posted by HEMI®Dart

I run as much negative caster as can be dialed into the axle and my tires are about 6 or 7 years old. Have about 70K miles on them. No funny wear patterns and decent tread left



I'll bet Dieselman has an Angle finder.

Yes, and a Laser, to find the centerline of the axles, and plenty of stanley clamps.



But, Caster has no effect on tire wear at all, period. And you can't run negative, it won't steer straight and I'll bet it will DW, I can prove it now.



I reset the Toe to basically 0, centered the wheel, and then ran the freeway, the truck will pull to the side with LESS positive caster.



I found the most sure footed setting is crank Caster all the way, about 5. 5 degrees, then test drive, feeling for which way it pulls.



Then decrease Caster on the side opposite the way the truck is pulling, in very small increments.



This truck is riding on rails now.



And if it increases tire wear, which I doubt, I'll take it

 

[JHardwick]

I was going to chime in awhile back on this "death wobble" deal.



The original thread ended with a "toe" problem. But, after racing sprint cars for numerous years with the antiquated straight front axle, I know that positive caster it what keeps them pointing straight. I'd sometimes run as much as 9*, but most generally 7*.



BTW, HEMI®Dart, negative caster will get you into real problems!



Shoot and imaginary line thru the center of the king pins to the concrete ..... that point needs to be in front of the center of the contact patch "or axle centerline". This is positive caster ... ... ... . I know of no vehicle that runs "negative" caster.

 

[HEMI®Dart]

I goofed.



I meant Positive caster. I get them mixed up sometimes.

 

[JHardwick]

It does get confusing some times, I'll atest to that!

 

[Driver72]

I'm definately confussed. Checking the torque often makes sense to keep everything running straight and true. I've got a nice 250 lb ft Proto wrench just gathering dust and would love to put it to use.



How about one of you guys providing a detailed explanation on caster/camber and how to check our trucks. Mine runs straight now but... .



I know I and many others probably have all the tools on hand to check alignment but I'll admit it is one of the secrets of life I know little about. If we are talking laser levels and angle finders these are realatively inexpensive to purchase (I can already hear her "what do you need these for").

 

[Midnight]

Your better off getting the truck to a garage with state of art equipment and have it checked. I is pretty hard for them to screw up taking the readings since the new equipment is pretty much idot proof. Either ask to stand and watch as the readings are taken or ask for a printout. Then you can be the judge. Goodluck guy's.

 

[lil red cummins]

i posted this some time ago and i am cutting and pasting it here:



here is the simple truth your front end shop doesn't want you to know. there are 3 settings for front end alignment. tow-in, caster & camber. these 3 settings are somewhat indendent in that if any one of them is incorrectly adjusted, it tends NOT to affect the others. But this is not an absolute.



tow- in affects tire wear primarily but can also be responsible for the truck "wandering" across the road. it is simply adjusted by adjusting the tie-rod end joints. some vehicles have one, some have two and if you have two, adjusting the correct one can be used to bring your steering wheel back to center.



caster is the adjustment made to correct for a continuous pull in one direction or to get the steering wheel to come back to center by itself after turning a corner. this adjustment is easier on leaf spring front ends since you can just put a caster shim between the axle and spring. if it is a coil spring front, you may be lucky enough to have an eccentric bushing in the ball joint mount (4wd). however adjusting this can also affect camber. pull on 4wd vehicles with solid axles is hard to correct because it would require twisting the axle. it generally doesnt happen. front coil suspension with A arms is the easiest, adding or removing shims at the frame.



camber is a visual thing. if you stand in front of your truck and look at the front tires relative to the backs, the top of the tire may be tipped out or in relative to the bottom. this adjustment affects handling around corners and can effect how you vehicle handles on heavily crowned roads.



What does all this mean?



in my experience of 35 years of performing front end alignments, FORGET the factory specs. if you have had a wreck or replaced components, or modified lift, they are good for a starting point. however when your right tire is wearing on the outside, you need to tow "out" the front end.



tow in can be easily measured with a measuring tape, (2) - 8" long pieces of 2 x 4 and a buddy. with your vehicle sitting on a flat surface and the wheels perfectly straight, place the 2 x 4's against the tread in front of both tires. stretch the tape between the two tires, making SURE that you both use the same tread. it doesnt have to be in the center, just make sure you both use the same one. (like 2 from the outside). after noting the distance (i. e. 65-5/8), move the block to behind the tires and measure on the exact same tread in the back. the rear length should be nearly the same and generally no more than 1/16" greater than the front. again this is a reference, but based on YOUR tire wear, i would adjust the toe in till both reading were the same. that means your tow will be at "zero". there is nothing wrong with this if it keeps your tires from wearing.



this by no means is a complete explanation, but it will give you a basic knowledge of alignment.



by the way, i have NEVER ever paid for a front end alignment, nor have i ever had a vehicle on an alignment rack. i DO however own a homemade tow-in gage which takes the place of your ruler and block setup. i have used the same gage on anything from a Model T Ford to a tandem road tractor. the key is to checking the wear of your front tires about every 4000 miles and make adjustments immediately if you see wear.



(end of previous post)



the caster adjustment has been covered well by jhardwick and dieselman.



jim

 

[jelag]

Back when I learned front ends, we learned that caster was the forward and rearward tilt of the king pin at the top... . or a line drawn through the upper and lower ball joints... . forward being neg. and rearward being positive.



Someone posted that the line drawn that hit the pavement was forward... . thats past the center line... and still is positive caster...



The more positive caster the more it wants to go straight... in some older cars without power steering you can feel the pressure increase to turn... when you add more positive caster...



Caster is not a tire wearing angle... and you can see a great example of caster... on a shopping cart at the store...



Camber is inward and outward tilt of the kingpin at the top... . again inward is neg and outward is positive... Camber is a tire wearing angle and will wear out tires... when it aproaches a number other than zero.....



The angle of the wheels change when you make a turn..... this is called toe out on turns. . and this change is to allow the tires to track different diameters... . when you make a turn... the inside tire makes a tighter turn than the outer tire... . there has to be some way to allow the tires to track straight ahead and than the inside wheel turns tighter than the outside wheel when you make a turn or you'd scrap off the tire... its not perfect on our trucks but I'm guessing it's as good as it can be without other problems... Also, remember that some vehicles tilt the inside tire towards the turn to allow for it to roll around the turn and not scrub off the tire... .



Toe is set... based on the compressability of the tie rod ends... the forces on the tie rods compress them... . so you set the tow with the vehicle sitting on the ground and as speed increases the tie rod ends compress and the wheels go straight... or as close to straight as possible... again toe is a tire wearing angle and being out of toe can a little can greatly increase tire wear...



A good front end tech. can when he feels the front tires have a good idea whats wrong with the alignment... you won't find one of these guys in a dealer operation... . most of these guys run a front end shop in a large tire store... . the one across the street from my business has been there about 20 years... . and rents the rack from the tire shop... I'm guessing that about 70% of the vehicles he checks he does nothing with... he just checks the alignment... because its in spec's, 20% he has to change to bring into spec's and the last 10% he has to take either out of spec's or to the end of spec's to make the vehicle run right down the road either to body sag, or damage to the front end... . some vehicles don't have a method to change the alignement and he has to install an aftermarket device to allow adjustment... .



On straight axles... the axle is bent in a press, like Fords old twin I beam.....



Jim

 

[Driver72]

Thanks guys, with this info I should at least look over the shoulder of the alignment tech and have a basic understanding of what he is doing.



Seems to me the first thing a good tech should do is check for abnormal wear patterns on the tires and ask the customer if the truck handles well.

 

[DIESELMAN]

On the older (<'03) the Camber is adjustable using shims in the upper ball/knuckle. It is an eccentric sleeve that is inserted the top and changes the the angle of the individual knuckles.



Since it is an eccentric, it has only two nuetral positions, Camber all in and Camber all out. All other positions cause changes to the caster value, which is why it needs to be set first, if at all. But it can be changed if needed. In our trucks it would appear that 0 is the correct angle in all cases.



Now I don't see a sleeve in the top of the AAM axle, but that doesn't mean it isn't there. If the axle is strong enough and cast/assembled correctly, it won't need this adjustability.



The Irritation with mine was that after being in the shop twice for this and three times for sway bar link breakage, they couldn't have ever put a wrench on the Caster adjustments. They would have seen this.



It appears that with the pounding that the Caster adjustments simply settle to the eccentric bolt low, cam high position which results in too little caster, and DW.



I have road tested, obviously not wear tested, my truck at every angle form 0 to +5. 5 degrees and can say that it drives best at max caster with about . 2 degrees offset to the left. Its like it is on rails.



As for an alignment shop, I don't think I'll be going there, this is really simpler than its made out to be. (I am speaking of course of real trucks, 4WD and not 1500's of course ).



And... . not to nit pick..... but I sure wish the shopping cart example would go away, its backwards and uses the wrong dynamics to describe a steering axle. Think Chopper.

 

[sag2]

DIESELMAN

When you had it at max caster, did you pick up any drive line vibration? I posted information a long time ago about the relation between the high speed vibration and too much caster. There is a point where you will cause the vibration because of the extreme U-joint angle.

 

[JHardwick]

Originally posted by jelag

The angle of the wheels change when you make a turn..... this is called toe out on turns. . and this change is to allow the tires to track different diameters... . when you make a turn... the inside tire makes a tighter turn than the outer tire... . there has to be some way to allow the tires to track straight ahead and than the inside wheel turns tighter than the outside wheel when you make a turn or you'd scrap off the tire... its not perfect on our trucks but I'm guessing it's as good as it can be without other problems...

Jim

This is also refered to as Ackerman Steer, wanna tackle bump steer, lol.



Another way to set toe which I believe to be more accurate is to make an ink mark with a ball point pen on both front tires at the 3 O'Clock position and measure that distance. Roll the vehicle forward till the ink marks are at the 9 O'Clock position and re-measure. This method eliminates error due to tread runout or bent wheels.



For you guys interested in doind any of this yourself, you can find all the measuring equipment here ... .



Speedway Motors

 

[Gypsyman]

DIESELMAN,



Did you have the right hand pull and if so what was your final caster setting to get rid of it?

 

[Tomeygun]

i second that Gypsyman:



I can park on the side of the road without touching the wheel at all! - pulls right very easily

 

[DIESELMAN]

Sag2 - No, maybe, I don't think so, no, not at all, I don't think.



Gyp/Tomey - right side has about . 2 degrees more positive than the left, runs down the road perfectly straight. It used to pull right.



All - I still have a touch of something when I run down the freeway at 75+ and there are undulations in the pavement, a little like something may not be happy and is oscillating just a bit. I am very sensative to anything happening after the DW incidents so it may be nothing, but its a little like the feel of a 69 Camaro Convertable on a ripply road, so... ... ... . I am still wrenching a bit.