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Old 03-25-2010, 01:45 AM   #21
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Re: Quadvan Death Wobble

I am upgrading our truck because i can feel it starting when going over a certain stretch of road. I DO NOT want it to happen while towing our 10,500lb toyhauler. That would most surely break something in the front end.

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Old 03-25-2010, 10:45 AM   #22
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Re: Quadvan Death Wobble

Turbo,
Quadvan is testing a dual setup and I'm seriously interested in your cutom fab. When you get pics please post or PM me.
Thanks...everything you have said makes sense and since you've actually done it with positive results I'm ON IT!
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Old 03-25-2010, 08:29 PM   #23
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Re: Quadvan Death Wobble

Here you go men!

Shock Part number is:
BE5-6253-H5

the mount on the axle is just a piece of 1.5" x 3" x 3/16 channel welded to a ~5 inch piece of 2x2 square tube. The whole assembly is offset to the drivers side by about 1.5"-2" so as not to crowd the busy passenger side upper tie rod.

First the beast:


Overall: (I know, I need to paint my welds, been meanin' ta do dat.


close ups:



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Old 03-25-2010, 08:31 PM   #24
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Re: Quadvan Death Wobble

This is the cheapest closest thing I have found.

http://trucktoyzstore.com/realm/pc/view ... tegory=368

Maybe mount the axle bracket upside down? Even upside down the ubolts on the axle tube would rub my crossmember. I have my axle pushed as far forward as I could stand. I think the shock bolts on the axle mount pointing up would cause interference issues. It's a tight fit in there! Anybody got any pics of a Quadvan front end setup? I am curious about the trackbar mount and frame mounts for the suspension arms.
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Old 03-25-2010, 08:44 PM   #25
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Re: Quadvan Death Wobble

I have about 7000 miles on it with the dual stab setup, no DW hints ever!
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Old 03-25-2010, 10:43 PM   #26
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Re: Quadvan Death Wobble

Guys,

Just try to make sure you're not masking serious steering problems with the steering stabilizers. Death wobble typically has a root cause, and the steering stabilizers do not eliminate that root cause.


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Old 03-26-2010, 04:45 PM   #27
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Re: Quadvan Death Wobble

Typically, leaf spring axles do not exhibit Death Wobble (to be refered to a 'Need to clean the drawers wobble). The axle is securely located by the leaf springs. With a leaf spring system you have serious problems if you have DW. Tire balance and other issue may cause minor wobble problems, but DW would mean something is very wrong.

Coil spring systems rely on track bars and similar to locate the axle. Any looseness here can lead straight to DW.

The worst cases happen when the axle can move side to side. The axle movement causes the wheels to steer in the other direction until the wheels pull the axle that way. Then the wheels will steer in the other direction until the axle moves, etc, etc, etc. Several times per second, depending on wheels/tires and other factors. The steering wheel and linkage don't move in this scenario. And a damper between the tie rod and the axle will dampen it. A damper earlier in the steering system (as a stock F350) will not have any affect in this case.

I don't really care if the dampers are a bandaid and hide a problem, as long as I never have DW trying to take my van apart again. I will continue to pay attention to steering wheel input vs. rate of turn and hope to detect any play before it gets really bad. But, I'll take the dampers and prevent DW everytime.

Mike
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Old 03-26-2010, 09:44 PM   #28
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Re: Quadvan Death Wobble

Quote:
I'll take the dampers and prevent DW everytime
Amen Brother!

The thing we are band-aiding is the crappy Ford design. I am convinced that long flat track-bars with flat equal length steering drag links don't exhibit this problem. I need two pages to explain my theories on the matter, but in short, high angle track bars cause a lot of lateral movement of the front axle when a perpendicular bump is encountered. The sudden uplift and the use of caster causes the tires to turn in the direction of the axle side track bar mount (right on our F350 setups). The more caster, the further ahead the kingpin axis is relative to the tire contact patch. This distance is the lever arm trying to turn the wheels. If you push sideways on a shopping cart, the casters turn in the direction of force. The sudden upthrust also loaded all the track bar compliance (slop, trackbar stiffness, bushing squish, lack of mount stiffness, frame stiffness, etc, nothing is infinitely stiff) in the same direction as if we were doing a normal hard turn in the opposite direction (left on F350 setups). The loading is because the massive axle doesn't want to go sideways, it has BIG inertia. After the initial upthrust our wheels turn right (shopping car effect) helping to unload all of the energy stored from the compliance. Once this energy is unloaded, guess what, the tires are now pointed left because the right turn jerk took all the compliance in the other direction pulling the axle left. The bump is more like an impulse (energy at all frequencies), these loads are mush more dramatic than a hard corner ever sees, this is why the DW isn't all the time. Steering wheel inertia also plays into the death wobble. Changing mass of the steering wheel can change the tendency of DW due to phase lead-lag angles relative to the tire wobble either canceling or compounding the problem.

Ford's bent track bar, big bushing at the frame side, high angle, along with a very high mass axle all add to the problem.
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Old 03-26-2010, 11:32 PM   #29
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Re: Quadvan Death Wobble

I was gonna say that! You both have convinced me to go to a double steering damper. I've learned a tremendous amount from this thread. The track bar angle on my van is nearly flat. I do have coil springs. I'm ripe for DW.
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Old 04-01-2010, 02:29 AM   #30
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Re: Quadvan Death Wobble

Wheel back-space, badly worn tires, out of balance tires, all these plus ball-joint wear problems can and do contribute to "death wobble" on any coil set up. As for removing the ball joints, never had a problem with coil tower being in the way. I got the dreaded "death wobble" after putting on wheels that I had purchased and was assured they were the right back-spacing, they weren't. The tires were BFG M/T KM2's, they were worn but good for one trip to mexico. It was the wheels that I was after. Put them on and got immediate "death wobble". Removed them no wobble. Found a double damper set up at Rize Industries, set it up with Procomp dampers. No problem since. Conclusion, check back-spacing,use good tires, and keep your ball joints greased. I also, don't think the front end design that Quadvan uses is not bad. I know this, because my van is the test mule for Quadvan. I have put ninety-seven thousand miles on it in the five years I have owned it and I have not babied it at all. Thirty-thousand have been off-road or poor road conditions. Just so you know, yes, I am a fan of Quadvan.
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