Diesel Forum - TheDieselStop.com - Reply to Topic
7.3L IDI Diesels (Not Power Strokes) Technical discussion of topics related to vehicles powered by the 7.3 Liter In-Direct Injection Navistar engines.

Thread: What causes DEATH WOBBLE ?????? Reply to Thread
Title:
Message:
Trackback:
Send Trackbacks to (Separate multiple URLs with spaces) :
Post Icons
You may choose an icon for your message from the following list:
 

Register Now



In order to be able to post messages on the Diesel Forum - TheDieselStop.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










  Additional Options
Miscellaneous Options

  Topic Review (Newest First)
09-18-2018 07:55 AM
Oneof6 The potential for impact induced vibration is not limited to Fords, Power PSD or any particular vehicle. Some front end assemblies damp, resist acceleration forces, more than others. Others like old Jeep front ends and trucks with leaf spring loaded steering assemblies. Sometimes one can move the point of resonant frequency to a frequency it is less likely to be resonated by adding mass, which lowers the frequency, or stiffening which raises the frequency. The target should be having the system natural frequency 25 to 40 % higher than the expected excitation frequency for units running below first critical. So the answer to your question is yes but no more than any object impacted in its operation. One can't remove the potential for natural frequency excitation one can only build a machine where the natural frequencies of individual parts and net assemblies are unlikely to be resonated during normal operation. Much preventative Engineering goes into rotors and assemblies like turbines, power plant fans, fluid drives and heavy equipment. Testing called "Bump Testing" is even done on large foundations when there is a suspected resonant condition that will coincide with the machines rotational frequency. That is cause, what owners are calling here "Death Wobble" is the effect and the solution is to not shade tree Engineer mechanism mods with man years of Engineering in them and expect no negative resultant. Front ends are not maintenance free, they can't have points of mechanical looseness, keep the tires balanced, preferably with a Hunter Force Balancer, a good steering damper and stick with stock tire sizes, that's what the assembly was Engineered for. Oneof6
09-17-2018 09:37 PM
ArcticDriver Does this mean inside every Powerstroke there is a “Death Wobble” lying in wait for the opportune moment to strike?
09-17-2018 08:24 PM
Oneof6 OK, I haven't answered this question in a long time. I will once more for those that are interested in understanding "cause" not treatment of symptoms. So far everyone is wrong and claiming that treating this or that symptom solved the problem, it did not it just moved it from a diagnostic perspective.
The issue is lack of stiffness, low mass, low energy degradation system and a phenomenon called resonance. Given enough source force impact any assembly can be made to resonate energy at its natural frequency or the net natural frequency of multiple assemblies mated together, system natural frequency. An object being impact resonated will act as a force multiplier of 10 to 50 x the source force. Given enough force some assemblies will maintain this system of vibration energy with a very low continuing source force after the starting impact. In the vibration diagnostic business that is called locked resonance. Once a vibrating system is created very little energy is needed to keep it going like swinging a child on a swing, the major energy required is starting the system to vibrate, then just a small cyclic push will keep it swinging. That is why some report that they hit a pot hole, a RR track, a curb or ran it with severely unbalanced tires and had to come to a complete stop to eliminate the shaking. The follow on source force didn't have to be as severe as the big starting impact to support the vibrating system.
Some things make it make likely, mechanical looseness, front end mods like bigger tires, bad steering dampers, and unbalanced tires. That's the cause, but its a problem that has to be managed by symptoms or peripheral parts. You cant change the "cause" physics, it is induced resonance amplitude. Think of a bell, impact it and it acts as a resonating force multiplier. Sure , you can dampen in but given enough source force it WILL resonate. Oneof6
09-17-2018 11:01 AM
tretpflyr Ford dealership used an aftermarket part (drag link?) that did not work out too well so they got the original Ford part in there and problem mostly solved. I am installing a new red head gear box that will correct for the loose steering and then the fix will be in. Thanks, y'all have helped a lot.
09-16-2018 03:59 PM
Rhonda Knight I had this happen on my 2 w/d f250 7.3 and mine seems to have been caused by bad tires and I had a large bracket that was cracked and separated that attaches to the frame. Had both replaced and it never happened again. Good luck Hope you find your problem.
08-25-2018 11:18 AM
tretpflyr Running 60 in mine.
08-25-2018 11:17 AM
tretpflyr I will follow your advice. Update. Took it to dealer for front end alignment and they found worn tie rods and joints as well as "fasteners".
I told them it might be that drag bar but they said no. I rest drove it then took it back because there was a bolt missing underneath that they forgot to put back in! Pic attached. After all day yesterday they admitted to me that they can not get it to align, must be drag bar. They are going to keep it for another week.

Oops, can't post pic, using iPad. Can't drag and drop.
08-19-2018 11:51 PM
gb23 Read my previous post. After many searches, I have concluded many things can cause it. Ford suggests 55psi for a soft ride so they can sell more trucks (make the ride more comfortable). My front tires psi is 78 and I won't go lower.
08-19-2018 07:45 PM
DevilDog6154
i dont know if your still needing it but this is a video that might help.
08-06-2018 02:29 PM
oldrebuiltdodge
Quote:
Originally Posted by tretpflyr View Post
I have a 2000 model with 7.3 2wd. I wonder if this death wobble is the result of worn components or if it is what is causing the components to wear. Can't figure mine out. At the dealership now waiting to speak again with the mechanic working on my truck. My pressures are run at 60 psi. Ford calls for 55 on the fronts. By raising the pressure to the max for the tire (mine is 80psi also) do you think this will fix it?
Look for loose tie rods, strut bushnigs, I-beam bushings, and ball joints. All of these things can cause the death wobble, as well as tires.
08-06-2018 12:11 PM
tretpflyr I have a 2000 model with 7.3 2wd. I wonder if this death wobble is the result of worn components or if it is what is causing the components to wear. Can't figure mine out. At the dealership now waiting to speak again with the mechanic working on my truck. My pressures are run at 60 psi. Ford calls for 55 on the fronts. By raising the pressure to the max for the tire (mine is 80psi also) do you think this will fix it?
06-16-2018 06:36 PM
gb23
'00 F-250 Death Wobble

11/99 I bought an '00 F-250 Power Stroke brand new. At 195K miles I replaced the front wheel bearings (Noisy and wheel slop). I think the death wobble began at around 198K miles. At 198K miles I had the the truck aligned. At 200K miles I installed new front Bilstein 4600 Series shocks. At 201K miles I replaced the front tires. The death wobble stopped then. At that time I increased tire pressure to 75-80 PSI in front and 70 PSI in rear (currently running 78 psi front, 74 psi rear). Truck now has 225.5K miles and death wobble has not returned. This truck is still stock with no mod's ever.
09-11-2014 12:58 PM
dieselboys I recently just found out from a friend that normally 80 % of the time the
"death wobble" is caused by the cummins torque monster which twists the frame and causes the rails to flex and fatigue. He was able to fix this problem with one of these Dodge Steering Stabilizers and it has lasted a little over a year. You can check them out since that where he got his or shop around, i heard a place called thouroughbred diesel also has decent ones available
07-12-2005 09:31 PM
Silver_Wolf2
Re: What causes DEATH WOBBLE ??????

Wow, sounds like your lucky to be alive! I think he fixed his problem, he mentioned it was the bolts sheared off the bracket I mentioned. Mine cracked, big time. Any way, glad your ok.
07-12-2005 07:43 PM
redstang410
Re: What causes DEATH WOBBLE ??????

I've had 2 different trucks which had a death wobble problem. From what i could gather, it can be caused by a number of things. All of which you have mentioned. From worn shocks, worn tires, slop in the steering box. play in the panhard bushings. Too much toe in. Worn shackle bushings. It could be caused by one or a combination of these. Mainly its slop or lack of motion control of the suspension.

I had someone tell my that my front tires were literally bouncing up and down off the ground as well as side to side during one episode. In my case, it happened specifically with one set of tires. When I put on a different set for wheeling, the problem went away. I tried steering stabilizers and shocks, but that didn't help. My steering box was bad, so i decided to change it with an AGR unit with hydraulic ram assist. Problem cured regardless of how bad the road, or how fast I go. I figured that the hydraulic ram does not allow the tires to oscillate left and right, causing the death wobble.

On the other truck i bought, the panhard bar, shocks and steering stabilizer were missing. The steering box was leaking, and the shackle bushings were bad. It would Death Wobble when hitting pot holes or turning at about 30mph. I rebuilt the steering box, Installed shocks, and the panhard bar, as well as replace the shackle bushings. The death wobble was gone. My alignment seemed a little toed out, so toed it in a little too much, and i could feel that Death wobble wanted to occur, so i toed it out again and it stabilized. I didn't want to install a hydraulic assist on this truck cause i don't wheel it as much.

I've seen death wobble on a number of trucks, and each case has a different fix that works. Usually you have to go eliminating the possible problems until its fixed.
This thread has more than 15 replies. Click here to review the whole thread.

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

 
For the best viewing experience please update your browser to Google Chrome