Death wobble/hop on my truck today

[Dane]

Running down the highway at 70-80mph, downhill. Passed over a dip in the road and the driver side front wheel starts jumping up and down like it's possesed. Applied the brakes lightly with no effect. More brakes no help. The hop didn't subside till I was down to about 50. Luckly for me no turns ahead so I could just steer and brake till it went away. Very scary If I'd had an off ramp or curve comming. The truck has 20K miles total on the odo, suspension is all stock except for shocks, steering damper and Roadmasters. Some mental notes, feed back please



1) The steering wheel did not move back and forth, the truck tracked straight.



2) Very definately felt like the front left wheel was doing the hopping.



3) Checked tire pressure and all 4 were correct- 55 front, 45 rear. Stock tires...



4) Shocks are Bilsteins with 10k on them and seem like new. Bolts are tight.



5) Steering damper is a Rancho RS5404 with 10k on it and works great, no wander over ruts. Bolts are tight.



6) Truck tracks straight, no wander. I did a quick check for loose tie rods, track bar, sway bar bushings etc... and all looked normal. Tomorrow I'll get out the FSM and check the track bar per the book. If the track bar checks Ok, I'm going to see if I can reproduce it on the same stretch of road and have my buddy take a look from another vehical an see if he can see whats shaking.



Any one had and then fixed the death wobble yet?

 

[JHansen]

Not on a Ram.....

... but a nasty case on my XJ once (with basically a downsized version of the Ram front suspension) that made my passengers fill their drawers .



If the steering stabilizer is new and tight and the front end is all tight, I'd have a look at the front alignment-IMO on the Jeep toe-in is fairly critical-toe-out does nasty nasty things. And caster helps to stabilize things-again IMO-other's experiences may vary.



Out of balance wheels seem to trigger it too-they say so can insufficient shock dampening although I can't see how... .



HTH

Jason

 

[**ICEMAN**]

i have had the death wobble in both my trucks. when i got it in my '94 the shocks,stabilizer,trak bar,ball joints, etc were all new. rotating the tires (front to back) stopped it for a while but it came back. i could make it occur on the same bumps etc. every time i hit them if i wanted but only if i was doing 65mph or more.

my '01 had around 10k miles on it when it happened. again the tire rotation stopped it for a while.

i took both trucks and had alignment done and set the caster to the positive position and so far ,,so good.

was the truck shaking so violently that you could barely set in the seat and had no control of the steering even though the steering wheel wasn't shaking? this is the death wobble!! and usually only corrects when you drop your mph down to 25-30.

also, both wheels wobble like there are 7 lug nuts missing and the 8th is backed halfway off.

did you have to change your underwear??

i believe that the death wobble and wheel hop are 2 different problems and unless you had the symptons like i described above you are dealing with a wheel hop.

let me know what you find out in your drive by test.

 

[Dane]

You described it real well Iceman, definately got my attention :--)



If the track bar checks OK, I'll have a good shop (assuming I can find one... ) check the alignment.



The right front tire is wearing faster than the left on the outside edge. I've been hesitant to change any front end settings cause the truck tracks real straight and I've read too many wander posts



Thanks for the input you guys, keep it cumin

 

[juicedcummins]

Mine has only done it one time at about 25k.

Took to the dealer, front end shop and they both said everything was 100% including the trackbar.

IT scared the CRAP out of me and that's just about impossible. :--)

 

[Jonz]

Death Wobble

You mentioned that you had Bilstein Shocks. Are these the yellow version or the re-valveable with the schrader valve.



The reason I ask is that my experience with Bilstein is that they are awesome shocks when properly valved. Our trucks have a fairly aggressave spring rate and the shocks need to match. Bilsteins tend to be a little soft in my experience.



You did'nt mention if this is 2 or 4 wheeldrive.





Troy

 

[NVR FNSH]

Any easy thing to check is to increase the caster yourself and drive over the bump that caused the problem. Just mark/record the caster before changing it. Do a search on my user name and you'll find lots of discussion on this topic.



Brian

 

[Dane]

Just found this old post from Brent, I'd saved it just in case. Look's like it may come in handy. I'll see if I can find a shop that will work with me to put my truck to these spec's exactly. If they gimme that funny look when I ask them, I'll move on to the next shop... Gotta love the TDR for the help we get from some good folks like him!



In a previous posting written by ???? (don't remember), they were complaining about a shimmy in their Ram 4x4 after striking bumps in the road.

I suggested that the front end alignment has either too little or too much caster, thus causing a caster shimmy. He did not like my response and changed his concern from a "shimmy" to a "bounce" (big difference), and insisted it was the shocks. Maybe it is, I haven't driven it. He also said the alignment "checked out". Here's the problem:

Alignment programs (and service manuals I believe), give a wide acceptable range for front caster on the 4x4 Rams. I believe the range is 2 degrees to 5 degrees (if that's not correct, it's pretty close). The problem occurs when the alignment tech (independent or dealer) tells you that the measurements "checked out fine", just because they were in this broad range of acceptance.

Caster readings that fall on either end of the scale are subject to caster shimmy, even though they are "acceptable". I had to align some 30 trucks and attend a 9 hour "Dodge Ram Chassis Dynamics Diagnostics" training session (fancy name, ehh?), before finding out that 3 degrees to 4 degrees is the optimal caster setting for 4x4 Rams that eliminates caster shimmy.

Below I will post what specifications I set Ram trucks to. First I want to give a little more info on correct Ram alignments so you can see if you had a job well done,

The eccentrics on the lower control arms ARE NOT for individual wheel caster adjustments (even though our alignment machine says they are). The eccentric sleeves in the upper ball joints are for adjusting individual camber and total cross caster (difference in caster between two front wheels). This is why replacement eccentrics are positionable in eight different ways.

Once camber and cross caster are attained with the eccentrics, the lower control arm eccentrics are then used to swing the caster readings into specifications. The two eccentrics must be swung in the SAME direction in EQUAL amounts. If they are not, it will create a setback condition (one front wheel further forward than the other).

FYI - Comparing between the two front wheels, caster will cause a pull to the smaller value and camber will cause a pull to the larger value. A truck set up with caster pulling in one direction and camber pulling in the other direction, can lead to a wandering truck; even though it is "in specifications"!!!!!!

If the eccentrics on the lower control arms of your truck are not pointing the same direction, the alignment was done incorrectly and the axle was "twisted" or "forced" into position to attain the acceptable values (seen them from the factory this way, go figure).

A correct alignment will set the truck up with a slight negative cross caster (truck has slight pull to left) to compensate for right hand road crown. Camber will be equal side to side slightly on the negative side. This will help maintain acceptable camber when hauling heavy loads, as the truck tends to lift in the front when towing. Camber will then fall slightly positive when towing.

Just because the alignment shop says "it's in specifications", that does not mean it is set up for proper performance and handling!!!!!!!!!



Specifications (my personal settings for every Ram I align): all specs below are in degrees.





Left Wheel Right Wheel

-------------- ----------------



Caster 3. 2 3. 5

Cross Caster -. 3



Camber -. 10 -. 10

Cross Camber 0. 0



Toe - standard specs, (maybe a little out if you tow a lot, they will pull in as the front end lifts up).



Brent

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