3rd Gen Engine and Drivetrain -> 2003-2007 5.9 liter Engine and drivetrain discussion only. PLEASE, NO HIGH PERFORMANCE DISCUSSION!
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After you fixed DW do you still get nervous

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Old 06-17-2008 | 07:52 AM
  #31  
Neight's Avatar
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Joined: Aug 2007
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From: Mesa, Az
I sold my PSD because of DW I didn't want the wifey driving it she would freak out if it happened to her. I have had zero problrms with my 06 but it is stock and staying that way.
Old 06-17-2008 | 08:39 AM
  #32  
XLR8R's Avatar
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Joined: Nov 2005
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From: Pattonville, Texas
Here's why I believe death wobble is bump steer induced:

#1 - Empirically, because it's a virtual loss of steering control immediately following the "right size" bump, pothole or other surface irregularity.
Observation alone is sufficient confirmation.

#2 - Theoretically, because the reasons I postulate fit the facts and do a good job of explaining (in a logical fashion) why the preventions & cures are effective.

Specifically, my explanation is as follows:
When the axle suddenly travels upward (such as over a bump), the fixed-length track bar pushes the axle towards the curb in relation to the frame; since the drag link cannot change length, it pulls back on the tie-rod (which is attached to both steering knuckles), causing the front tires to turn slightly towards the road centerline.
Additionally, solid front axle pickup trucks seem to have an awful lot of negative camber for an alignment spec that wasn't designed to be adjusted as SOP... in the HD Rams' case - I attribute much of that to the relatively large wear spec of the ball joints (upper max of .060" lateral & lower max of .090" vertical IIRC). Of course, this negative camber (the top of the tires leaning inwards) - which is readily visible on most of our trucks if you squint creates camber thrust whenever the front tires' weight-based coeffecient of friction (traction) is out of balance with each other, such as encountering a bump or as a result of centrifugally-induced weight transfer.
This phenomenom is responsible for the single sideways lurch many of us are familiar with.
Centrifugal force causes weight transfer to the outside of the turn (the curb in this case), which slightly settles the passenger side coil spring - heightening the drag link effect (the closer the axle gets to the frame, the more the drag link will steer the knuckles towards oncoming traffic, assuming the steering wheel is held in position).

The problem arises when the soft rubber-cored OEM track bar bushings allow the axle to laterally bounce back & forth - that movement drags the steering knuckles back & forth as well.
I don't think the HD Ram front suspension is a bad design (shucks - I've logged over 300K DW-free miles on 4WD QC 2500s... mostly on oversized BFG AT KOs, althought I did switch to Toyo MTs a couple of years ago for their weight capacity), but I do think the road manners would be better if the track bar was parallel to the axle at rest, instead of being 4" high on the driver's side.

Of course, it's probably more accurate to say that DW can be (not must be) induced by any sufficient lateral force of momentary duration that acts upon the front axle.

As far as all of the ancillary issues, the best way to realize a better handling Ram would be to redesign & fabricate practically everything between the axle and the frame... but that's not gonna happen, so most folks are happy to upgrade what they can to fit their needs. For example, even though I'd be the first one to appreciate having a roll center above ground rather than below it, I really like how the longer control arms get the tires out of the back of my fenderwells with the leveling lift.

I'd expect the 3rd Gens to lose less +caster when lifted than the 2nd Gens, which have a 3/4" longer upper control arm swing radius in comparison, but still should be a net loss...

My philosophy is to strengthen & stabilize a suspension design, as I believe that results in the most bang for your buck.

Too many variables to list for a meaningful discussion of specific brands or tuning methods, except for general trends and gross disparities... since plenty of people have enough anecdotal evidence to support differing conclusions.
Old 06-17-2008 | 08:55 AM
  #33  
Patriot2500's Avatar
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Joined: Nov 2005
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From: montville,nj
I think about it every time I am on the highway with my truck as I had DW twice so far in 4 years. First time it was the shocks, second time it was the tires.
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