2nd Gen Non-Engine/Transmission Truck Started Shaking uncontrollably

[Clinton]

I'm trying to quote for the first time, this may not work out just right.

KRS Has anyone who has a DT track bar installed ever had the wobble after the DT install?

Yeah, me.

Please explain why you think your 'design' changes would improve the handling of the truck - drag link connection, steering stabilizer location, sway bar bracket/linkage. I think we can all agree that the track bar ball/socket is under designed but I'm curious to hear the rationale for the changes you suggest.

The rationale for the changes would be better performance and higher durability. I was careful to relate these items to poor performance in general and not the DW condition specifically. The drag link/tie rod is lame. It creates a joint within the linkage that is unnecessary and drives the price of the RH tie rod through the roof. The sway bar linkage doesn't seem to hold up very well on mine, I'll try Moog links on this next effort, I suppose I'm just bitter about it. The stabilizer looks like it was stuck on there at random where ever they had room left. I haven't looked at it since I replaced it and I'm on the road without the truck, but seems like I had a better postion all thought out at one time.



Mainly, what I was getting at is that the front ends aren't the greatest and there was way more I'M RIGHT AND YOU ARE DEFINETLY WRONG in the thread than I care to see. Mine's a tire problem, but I'm not going to insist everyone else's is too. The DW is the same phenomenon (sp?) as the caster shimmy, the death march, etc. I've heard different folks call it by different names, but I've never heard of one single cure.

 

[krs]

How about: Has anyone who has installed the "Darin's Steering Strut" (or whatever you may call it) had the wobble after that installation?



Maybe we're dealing with a frame that's weak and gets into a resonation like a giant tuning fork.



We had a '78 3/4 ton Dodge pickup that was used as a towtruck by putting a Holmes boom in the bed. It was a stupid thing to do but the weights were not large (postal jeeps). One day one of our guys went around a corner and his road box slid over and activated the boom winch switch. The cable was hooked down to the back bumper. By the time he got to the shop that truck was bent so bad that it looked like a swayback horse.

So the cable was routed through a floor ring in the body shop and the winch was used to pull the frame back straight and the truck was used without further trouble for about three more years. THAT Dodge frame was weak.

 

[JWEST]

I agree with Clinton that there should have been some better design work on the front end of the 4x4's. If you look at the trucks year by year, you can see the changes DC made bit by bit, and you might think some of them would be obvious, and some not so obvious like the elimination of the CAD.



If you ask a Ford SD guy if he's ever had the DW, and he says no, we know why. Leaf springs and a steering linkage with less angularity are the answer there.

 

[JWEST]

Mimprevento,

I have no doubt that double shocks will take care of the DW, but it's a remedy only. It's not the root cause of the problem. Just like the lack of a steering stabilizer does not necessarily mean we need one. There is something causing a violent, low frequency vibration in the front axle or suspension and the stock shocks are not adequate to dampen it. Double shocks might be able to dampen it, but they don't cause it in the first place. There is some element in the mass (axle, tire, wheel) or spring (tire, coil springs) that is storing and releasing energy in violent fashion. If the DC engineers had experienced it while testing their trucks, they either figured out a way for it not to happen when the delear is riding in the trucks, or they figured out a way for it to happen infrequently enough to be statistically acceptable.

 

[jtwcummins]

Death Wobble

I have had my 97 4x4 since 1/97 and never have had the DW. I would knock on wood, but it gives me a headache.



Everthing listed and discussed can contribute to the problem. The steering for the 4x4 is marginal at best and the 1000lb Cummins makes it worse. Any worn or out of spec part can cause this problem. In addition the trailing arms-track bars (for Ford folks) holding the front diff in place are weak.



Went to a 4x4 parts store to check on replacement track bars and found a set of Rancho stock height trailing arm replacements that are very heavy duty. Had them installed. These are boxed steel and seem to help. Wouldn't have known about them except these are Ford/Chevy guys and track bars were trailing arms to them. Big heavy red bars look kinda neat to. I have done the Luke's Link to the trackbar since the factory units can be worn out in 4k miles and the steering box brace. Had the front end aligned per these instructions. I have no wander, pull or anything other than straight line tracking. Was amazed at how much steering correction was needed before, can almost watch the scenery go by.



With 4. 10 gears I don't cruise at 80 since that is close to floored and the guv is talking to me. Running Dunlop 265-75-16 rubber. Truck is a pleasure on the freeway now.



I am adding something I picked up in TDR from the past about alignment and force shop to do it this way while I watch.



First of all let me say this: Damn all of you nice people for

wanting me to stay with aadt

Anyway, I'm not much for having a good short term memory, so bear

with me.

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

ASE Certified

Gold Certified Chrysler tech

 

[krs]

Makes a lot of sense, Brett. Will it account for the truck which travels far, often tens of thousands of miles, without incident only to one day hit a bump, pothole, expansion joint etc. and fall into violent side to side wheel wobble, or shimmy?

 

[Extreme1]

Thanks Brent, now my response can be short!

Brent is right. The wobble that is experienced is largly attributed to not enough caster, more will generally fix it even if there are other contributors.



Consider this, as a vehicle is traveling down the road, the wheels are NOT wobbling back and forth (or trying to steer all the way in one direction) because caster and the vehicle weight are keeping them pointed forward.



Now, think if the caster is, as Brent described, too low. Hit a bump and, due to the solid axle causing both sides to be affected, the wheel hitting the bump gets deflected in a direction. Caster forces the wheel(s) back in the proper direction but, because the caster is too low, it goes over the 0 point then begins to return and overcenters again. The energy to make this contunue is input to the system by the tires being pushed down the road and the tires themselves acting as a lightly damped spring. Not up and down but in a twist on the steering axis.



Loose steering parts including the trac bar will all add to the effect by allowing more individual wheel travel.



As for the situation that new tires cured the DW, tire tread has a HUGE damping effect on vehicle handling in the direction I refer to. That's why autocross cars run tires that are machined down so almost all the tread is gone. Next time it does it, try the alignment to Brent's specs (get a print out before and after and watch them do it to be sure they do it right).



Glad you posted Brent!

 

[jtwcummins]

wobble wheel

Brent posted this a while ago. I put it up there leaving his name on it. credit where it is due.

I have this as a text file and print it every time I go for alignment. If tech has lost look I move on.

 

[NVR FNSH]

The drag link pivot is located on the 'tie rod' at appx the same location as the track bar end - this is done to minimize bump steer in a straight ahead situation. Granted, the 'Y' linkage is lame because of the toe-in change but moving the drag link to the passenger knuckle is a compromise as well.



I'm really curious how you are wearing out sway bar links. Are you bending the links or wearing the bushings?



Regarding Rancho's 'big beefy' control arms I'd sure like someone to do a buckling analysis on the Rancho arm vs the stock arm. I'm willing to bet they aren't that different... .



Brian

 

[Extreme1]

Get the specs on the tubes they use. The material, diameter, and wall thickness. I'd bet that they are nearly double the strength in compression. I think the only loading they see is compression, less tension and small bending moments.

 

[jtwcummins]

The control arms from rancho are almost 3 times as strong as the factory unit, per rancho. They use steel almost twice as thick as factory and are in a square box shape. There is a difference in the feel when a pot hole is hit, very solid feeling in steering wheel. DC suspected excessive flex of the control arms contributed to the gen 2 brake pulling problem.

 

[jtwcummins]

The only reason I found out Rancho made these control arms for stock height RAMs was I inquired about track bars. 4 wheel accessories is mostly Chevy/Ford so track bar or trailing arms were control arms the the guys behind the counter. Showed me the part and I had them installed, they are very heavy duty. Made like the ones in there lift kits

 

[3atatime]

I definitely know what's up

I've had my '96 for a year and a half and have had very little trouble out of him. I know exactly how you feel. I finally took it into the shop and they replaced my steering stablilizer and rotated my tires and aligned the front end. That cured the problem for a while. About 6 months later the same thing was happening again except the vibrating wasn't as violent. I checked the steering stabilizer and it was tight. I took it to the shop again and they aligned it for me. I also put new tires on the front which I badly needed. I was convinced that the alignment plus new tires wouldn't solve the problem like I was told, but months later the problem hasn't reoccured.