Death wobble may be the death of me.. suggestions. (1 Viewer)

[richardmvaldez]

I had the same problem on my 80 and 40 the tires were not round (old h1 tires and recentered wheels) turned out to be the rubber. just had it again on my work dodge. one tire is not round and if that tire is on the front axle it is violent. the only way to tell is if I roll the tire across the shop floor smooth and flat and the tire will start to wobble and fall over. good tires will just roll. hope this helps. find a friend with wheel tires that fit and swap them around. it was vary frustrating.

 

[ppc]

Get someone to drive alongside you and see if any one tire is jumping around.

 

[ajax1]

Death wobble
Check pan hards make sure bushings are good bolts are torq to proper number
Front arms torqued to correct amount?
Trunnions bearings replaced on knuckle build?
Not enough caster? Have you had alignment to see your numbers? Should be between 2 and 4 positive on sheet they give ya , would not think you would get that with just the bushings
Every set bfg I have owned shake at 65 to 70 then balance back out
Now if you have vibrations I'd look at rear shaft being 4 inch comp lift your prob at 5 or 6 inches so rear shaft could be off giving bad pinion angle , pull shaft lock cdl and check, also if four wheel farts did the lift I'd double check all the link bolts
If rear shaft is off you can do adjustable rear upper links to correct or cv

 

[dogfishlake]

Swap the front tires with the backs, should at least identify if you have an out of round front tire, sure seems like it.

 

[Nay]

A few things jump out here:

You have a lot of lift. This would have put both driveshafts out of phase. What this means is that the t-case and axle u-joint angles are not equal (or equal and opposite) and the increased angles from lifting will exacerbate the issue, because a u-joint operating at an angle moves in an elliptical motion, not circular. The greater the operating angle, the more elliptical it becomes.

So if the u-joint on one end is traveling on a different elliptical path than the other, the driveshaft is going to vibrate and possibly shake. No amount of rebalancing will fix this.

Next, you have caster correction, and caster and axle pinion u-joint angle are tied together. You cannot adjust one without the other. You installed a DC shaft, but it may not be properly in phase just as the stock shaft was out of phase. You choose a front driveshaft type to ensure phasing (no vibes) and proper caster (no wander/wobble). Replacing one type with another is meaningless unless it is properly aligned.

A DC (double cardan) joint has two u-joints that cancel each other out at the t-case end, so the lone joint at the axle end has to be operating at a near zero angle or it will vibrate (the DC end does not move in an elliptical path - or close enough for the purposes here - and a u-joint at a zero degree operating angle also moves in a circle). So if your lift height and caster correction are not lining up that DC shaft, you have a pinion angle alignment problem - caster has to follow pinion angle driveshaft alignment, not the other way around. This is the number one reason why just going big on suspension lift should be evaluated very carefully, because a rig on the low end of factory caster may remain out of spec or the front shaft will vibrate with AWD. Part time conversion with lockout hubs or build a new axle. Or reduce lift and gain caster.

Despite these potential front end issues, the primary problem is likely the rear driveshaft being misaligned. That is too much lift to expect a standard u-joint driveshaft to spin cleanly even if both u-joints are in phase, which they almost certainly are not.

So the honest answer to your problem is that you put on way more lift than is needed for those tires and have likely introduced driveline geometry issues that can be corrected if you want to spend the money, but worst case it could be big money in the form of a custom front axle.

Next steps: first you have to ensure alignment on that front shaft. Once done, get an alignment and see what your caster readings are. If low, the front end can wobble including actual death wobble, but that is usually brought on by hitting a bump.

Then you most likely need a DC rear shaft with adjustable upper control arms to set that pinion angle properly (tilting the pinion up until the pinion and u-joint are operating at the same angle, or -1 degree for the pinion to account for torque load that will raise it a bit into line under throttle).

Here is an in depth read. Note that theoretical max u-joint operating angles and out of phase issues are influenced by RPM - that 68 mph speed is highly suggestive of driveline vibes (mine does the exact same thing but very minor vibes at the exact same speed - it goes away cargo loaded because the rear suspension compresses a bit and brings the u-joints back in phase).

Good luck and happy reading! If you want to just take another money shot, call Mr. Slee and buy adjustable upper control arms and a DC rear driveshaft, and learn how to set that pinion angle from this article:

Driveline 101

 

[Whileemptyheadsdream]

Just to clarify The Death Wabble
Did you do a full knuckle rebuild ? There could be many things that could be the culprit here. I will post one because Its dangerous If not preformed correctly, from a past post. Trunion's

The housing that your axle goes through attached to your steering Tie rod ends. Its what turns your wheel, there is abearing on top and bottom that Must have proper preload or you will have Death wobble. Here Is a quote from Dave 2000
Insufficient preload on the upper and lower trunnions are IME the biggest single cause of the 'Death wobble'. Check it carefully with a spring gauge. The death wobble needs something to 'set it off', the wheel bearings would have to be very loose to start it off, so loose that you would have virtually no brake pedal after driving about 10 feet. An out ofround tyre rarely is the cause as this gets noticed in other ways (noise/vibration). Even the steering damper has been blamed but again IME the damper will not stop the real thing, it may help but the damper is applied to the steering and not the suspension. A death wobble caused by worn or loose top and bottom swivels is not going to be helped by changing the damper, the affect s simply to strong to damp down.

As an sides and not aimed at anyone in particular, I have noticed that the 'Death wobble' gets announced for a simple vibration caused by an out of balance tyre or wheel, the genuine death wobble is not something that happens every time you hit 60 MPH, or a small shudder under braking. The real thing normally happens when on a curve and set off by a simple bump, the loading on the suspension being shuffled from side to side, or braking quite heavy i.e. when the suspension components are loaded up, this will throw the vehicle about quite violently and to the uninitiated can be quite scary, for future posters spend some time to make sure you have the real thing.

regards

Dav

Also If used, bushings won't do She and will cause problems. You at least need plates or I would Install Arms.
Good Luck !

 

[mct75]

I may have glossed over this, but have the wheels been rotated? If it's a tire issue, the feel would be changed significantly by moving the problem from front to back.

 

[White Stripe]

Im going to agree with a above post that the caster correction may have set your ujoints with too much of a variance. To properly setup the use of a double cardan, your pinion needs to be pointing at the transfercase output flange. If it isnt, then it will cause a high speed vibration. But if you adjust the pinion like that, it could throw off your caster. I would go back to the old driveshaft with single ujoints, set the pinion angle so that both the tcase ujoint and the pinion ujoint are set correctly using your caster adjusters you have. Do some research on how to properly set ujoint angles. Once you have that set, check what your caster is and report back. Also check your rear drive shaft ujoint angles. You may need to adjust that as well. I don't think a double cardan shaft is nescessary on a 80.

 

[skyline223]

Thank you all for alot of helpful input and very good food for thought. I realize that a lot of time went into quite a few of these posts. The recommendations are extremely helpful.

Nay - thank you for the plethora of information regarding pinion angle issues due to lift, etc. Tomorrow I will get out and get a solid read on all of my pinion angles to see where I truly stand. At this point I'm willing to do about anything to get it right. I'm not one to cut corners and never had any intention to from the beginning.

While empty - I did perform a full knuckle rebuild. As referenced in a popular knuckle rebuild video that floats around here, I replaced the trunion bearings with Koyo replacments and races and used the factory shims torqued to spec. Without a doubt I have been using the wrong term to describe my vibrations.

Here is something worth noting at this point. I took the truck for a drive this afternoon and the problem seems to have gotten worse out of nowhere. The vibrations at 70 mph are still very potent, but vibrations have also developed at lower speeds as of now. 45-60 mph warrants intense lower frequency vibrations that shake the steering wheel back and forth. As speed increases the vibration seems to transition off of the steering wheel and to the entire truck. To my body, it sure feels like a tire issue. But with the expertise here on the forum I am not ruling out for a second that it is a driveline issue.

Once again, I'll begin thoroughly checking my driveline angles tomorrow and report back. In the meantime I am going to try harder to find a set of stock rollers to begin elimination.

 

[baldilocks]

What about your shocks. I had bad death wan lemon only 05 dodge cummins and it boiled down to the shocks.
A bad tire from the factory is a possibility. You said bushings check out but.....
Energy in must match energy out. This problem is simple. Go back to the beginning.

 

[skyline223]

Shocks are new OME installed with the rest of the lift. All bolts are snug and bushings are good. Anything else to look for?

 

[BlueCruiser84]

If you are feeling a back and forth in the wheel I would vote a front tire. As someone mentioned, swap the front tires to the back one at a time. See if the vibration/shake changes from the steering wheel to your butt.

Borrow a set of tires.

Chock the wheels, put the T-case in neutral or pull a drive flange, jack up one corner at a time and spin the tire by hand. If it's bad enough you'll see a broken belt or an out of round tire.

I would quit throwing parts at it until you do some free stuff.

*edit* your cruiser looks pretty clean so this might not apply. Make sure the wheel mounting surface on the wheel and on the axle are clean and smooth. My cruiser sat for a while and had some pretty significant corrosion on both.

**another edit** Get your caster numbers. I would think they are ok with the MAF brackets, but its' worht a check. There is a sweet spot around 0* where wobbles are MUCH more likely.

 

[Willopat]

I would start with the cheapest thing first. The rear u-joints. I just did a knuckle rebuild and a ome 2.5 inch lift 33 inch tires. When finished I had a clicking sound from the front shaft. Changed the u-joints and fixed it. The other day was the first time I drove it at 65ish and I had a mild vibration. So my next step is to replace the rear. I should have done this when I did the front oh well live and learn. My 80 has around 375000 give or take10000 or so clock stopped at 301. That being said the u-joints are worn out plus the wear points have changed. I plan on doing this in 2 weeks. I will let you know if that fixed it. If you beat me to it let me know.

 

[skyline223]

Willopat - I just had the u-joints replaced in the rear shaft a few days ago. For me, it unfortunately yielded no improvement.

Here are some driveline angles for consideration with the truck at ride height.


Rear axle pinion

Rear driveshaft angle

So that gives me a 4 degree pinion angle at the rear pinion. Is this too much? It also seems strange that my pinion is angled down. Isn't it usually an issue of it turning up after a lift?


Angle of rear driveshaft/pinion at T-case

Here are the measurements for the front double cardan shaft.
Angle at front axle pinion.

Front driveshaft

Front shaft comes in with a pinon angle of 3 degrees

Not sure if this helps at all to post this info. But trying to figure out just how out of whack it is. Thanks.

 

[skyline223]

Sometimes pictures say a thousand words also.. so here is a rough idea of where the truck sits height wise. And give me a break on the cleanliness.. poor gal hasn't seen a trail in longer than I'd like to admit. Problem is.. when you live in Memphis you have to drive minimum 4 hours to get to any respectable trail.. and until this issue is resolved that won't be happening..


Rear

Front

Overall

 

[Willopat]

Very nice truck. Sorry I could not help hope it helps mine. Have you tried calling slee offroad they seem very knowledgeable.

 

[dogfishlake]

All vibrations aside, that's a damn fine looking 80! Carry on.

 

[dogfishlake]

Seems like those front arm drop brackets (if that's what I'm seeing in the pic) would eliminate the need for a DC front shaft.

 

[White Stripe]

So if your rear tcase flange is pointed 5 degrees down(its hard to read from a photo and if your measurements are accurate and on a truly flat surface)you rear pinion should be pointed up 5 degrees with a variance of 2 degrees between the 2. So you have quite a big variance their, enough to cause a bad vibration I think. For the front, the shaft looks like it measures at negative 10 degrees and the pinion at negative 6 or 7. One thing you can do to verify if a drive shaft is causing a vibration is remove the rear drive shaft, engage the center differential, and drive down the freeway, if the vibration is gone, its likely the driveshaft on the rear. You can also just do the same but remove the front shaft, drive down the road, and see if the vibration is gone.

 

[Nay]

So if your rear tcase flange is pointed 5 degrees down(its hard to read from a photo and if your measurements are accurate and on a truly flat surface)you rear pinion should be pointed up 5 degrees with a variance of 2 degrees between the 2. So you have quite a big variance their, enough to cause a bad vibration I think. For the front, the shaft looks like it measures at negative 10 degrees and the pinion at negative 6 or 7. One thing you can do to verify if a drive shaft is causing a vibration is remove the rear drive shaft, engage the center differential, and drive down the freeway, if the vibration is gone, its likely the driveshaft on the rear. You can also just do the same but remove the front shaft, drive down the road, and see if the vibration is gone.

Agreed that those initial gravity protractor measurements suggest driveline angle issues.

Up front, a 3 degree variance in pinion to driveshaft angle means a 3 degree operating angle on that u-joint. It has to be very close to zero (the pinion and driveshaft are at the same angle) for that DC shaft. That driveshaft should be growling for sure at those higher highway RPM (68 mph and up). I would talk to Slee with the thought of using his caster correction for the 6" kit. Basic correction here was not enough (and shouldn't have been for those springs).

For the rear, don't worry about measuring the driveshaft or pinion angles. Measure the actual u-joint angle by making sure one of the caps is pointed straight down and then use a socket to extend the cap for a flat surface for your gravity protractor. The angles for the t-case and axle side u-joints should be nearly equal (or equal and opposite such as 3 degrees and -3 degrees). Even in phase, once you are getting up to 5 degrees or so those joints may be unhappy. Think about that entire assembly running in an elliptical arc at higher RPM. For a lot of highway miles, I would convert the rear to a DC shaft with upper adjustable control arms to set that axle side u-joint angle to 0 / -1 degrees.

I extended my lower control arms by 3/8" to return the wheelbase to stock and re-center the wheel as well as lower the pinion a bit. This helped bring my u-joint angles back in phase, but it's an old driveshaft so can only do so much and those joints are still at about 4 degrees when 3 or less is optimal for long term higher speed road use.

The 45 mph onset of steering shake is definitely suggestive of a lateral tire balance issue. Balance beads and the like cannot influence lateral balance (they address forward roundness variations) and those issues can be difficult to fix as they can require a lot of weight on one side of the rim. If your tire shop is using weights inside the rim only, it is very likely they have not sufficiently addressed lateral balance on a more aggressive tire. If you told them not to put any weights on the outside of the rim, don't say that next time .

Also check your PSI - I would not be running big tires at the PSI often recommended here based on converting from p-metric. That turns your truck into a brick. I run 37" BFG ko2 at 29 PSI on 8.5" rims because at higher pressures the tires will crown and wander and it is so jarring over bumps. I just bought an '04 Sequoia and could not run down some extra shake in the front and I have access to a friend's for comparison to feel the difference.

I've just upgraded shocks and struts, and the truck had a ton of shop maintenance $$$ thrown at it by the PO. Turns out PO had the 265/70/17 Dynapro ATM at 38 PSI. I put them back to 33 (factory is 32 PSI and this is one size bigger) and everything is nice and smooth again.

Bottom line: I think you have a lateral tire balance issue showing up with side to side steering wobble at 45 mph and both driveshafts have alignment issues showing up at consistent higher highway RPM (68 mph).

Both issues are definitely curable. Getting sick of lateral tire balance issues finally is what got me to ditch trxus MT for BFG ko2. That tire is silly civilized for being a 37 and I don't have any balance weights on the outside of the rims for lateral balance issues. Although I did pay an extra $10 per tire to Discount Tire Direct to get the extra tire/rim diagnostics and it's possible that $40 meant they had to find me 4 perfect tires for the rims I bought at the same time. Either way, the result was money.

Words to the wise following this thread: if you are going more than 4" in lift, you can either buy the expensive kit that addresses the extra complications or bleed it out. Not a critique of our OP, just a reality. 80's are very tolerant because you can get a lot caster back by converting the stock driveshaft in its broken back design by shifting to a DC shaft. Usually you just have a DC from the factory and lift reduces caster one for one. Or you have IFS