Reply
 
Thread Tools Display Modes
 
Old 04-09-2015, 06:18 PM   #1
Member
 
sidetrak06's Avatar
 
Join Date: Nov 2012
Location: Denver, CO
Posts: 55
Death Wobble - Possible Resolution

I have a custom 2000 E350 w/ an 06 F350 front end I have roughly a 6" lift and 35 x 12.5 Toyo M/Ts. The 4x4 conversion was done by Boulder Offroad Vans in Colorado. I thought I would share my experiences with death wobble since I have been through the ringer and some of you may benefit from my troubles.



Immediately after the 4x4 conversion, the vehicle drove great and had no steering issues at all. By the end of year 1, the stock steering gearbox was shot and had lots of slop in it. I tightened up the worm gear with the set screw and death wobble showed it's face to me for the very first time. It turns out having a lot of slop in the steering system can prevent death wobble, it's not until you ALMOST get rid of the slop that you have issues.



Next, I decided to swap the gearbox and that temporarily eliminated the death wobble. Soon after, the drag link was the next weakest link and the hole where the steering stabilizer shock mounts wallowed out into an oval and death wobble came back. I replaced the drag link and found more play in the attachment of the pitman arm to the gearbox, which was due to damaged splines and could not be tightened further. A new pitman arm and death wobble was gone.





After about 4 months, the death wobble was back and this time it was damaged splines on the pitman arm again. I did a bit of research and figured that my setup was causing too much stress at this location and I needed to reduce this as much as possible. I had a custom pitman nut made with a shaft on it so I could add a support bearing to take the load off of the steering gearbox output shaft.



This worked for a while until again, the splines on the pitman arm/gearbox output shaft were destroyed.



I did some more research and figured the best way to reduce the stress at this point was to add a hydraulic assisted steering ram. I bought a Red Neck Ram kit with a 1.5" diameter cylinder and fabbed up a custom bracket for the attachment to the tie rod and axle. I bought a new (refurbished) gearbox and sent it out to be drilled and tapped along with a new power steering pump to be modified for higher output flow.







At this point, I truly thought I was done. The steering felt great and the death wobble was gone! There was no slop anywhere in the system and life was good. Except for one thing...I had an alignment issue that was wearing the front right tire and causing the vehicle to constantly pull to the right. I looked around for an alignment shop that could handle this large of a vehicle and decided to go with 4Wheel Parts.

I left the vehicle there and about 4 hours later they told me that the alignment was perfect but that now it has a horrible death wobble if you hit a bump with the front right tire between 30 and 50 mph! The tech said that he was completely baffled since the steering system had absolutely no play in it and the tracking bar bushings and ball joints were in great condition. By the end of the day he told me that he was able to "tweak" the alignment and got it to drive without death wobble.

I was seriously skeptical of what he did so I drove it for a few weeks. Something was definitely not right, it still pulled to the right (slightly less) and although it did not go into a full epileptic seizure, it sure thought about it a few times. I did not trust the alignment so I brought it to High Country Performance to check it out. They said the castor was maxed out at 3.7 deg (good), the camber was 0 deg (good) but it was toed out 0.25" (not good). This was done to hide the death wobble. They checked the entire steering system and found no reason for this vehicle to have death wobble. Again, another shop was dumbfounded.

I had them set the toe back to 1/8" in and I mounted a GoPro on the front bumper looking at the steering system and took it for a drive. Knowing I could get it to death wobble by dipping the front right tire into a nice pot hole. This is what I found:









Looking at video #3, you can see that the axle is actually moving forwards and backwards as though the radius arms bushing are shot or not stiff enough. It seems that this axle movement is forcing a turning radius on the steering system, which has to respond by moving. This oscillates and hits a resonant frequency where it goes into a full blown death wobble. The tracking bar bushing looks good and doesn't budge. All other components that I can see are doing their job and don't have any play.

Now, I am having the shop install adjustable uppers to the ball joints so that I can stretch the camber all the way to 6 degrees, hoping that this will help the situation. If that doesn't take care of it, I will pull the radius arm bushings and see what kind of shape they are in. I need to see if there are harder bushings available or if these ones are just damaged.

Ultimately, I am very surprised to see this kind of axle movement and thought that there might be some other rigs out there that fixed the steering system and still struggle with death wobble. As I continue to play with this I will post here and give updates.

Wish me luck...
__________________

sidetrak06 is offline   Reply With Quote
Old 04-09-2015, 06:42 PM   #2
Senior Member
 
boywonder's Avatar
 
Join Date: Jul 2013
Location: So Cal
Posts: 3,027
Re: Death Wobble - Possible Resolution

Excellent videos! Good luck in your continuing search...

__________________

__________________
2008 E350 RB passenger 4WD SMB penthouse
2013 KTM 350 EXC
2008 KTM 250 XCF-W
2000 KTM 200 EXC
2003 Honda Element
boywonder is offline   Reply With Quote
Old 04-09-2015, 06:45 PM   #3
Site Team
 
BroncoHauler's Avatar
 
Join Date: May 2007
Location: Southern New Mexico
Posts: 9,127
Re: Death Wobble - Possible Resolution

FWIW, and I have no firsthand knowledge, but I've heard many times never to adjust the set screw on a steering box.


Herb
__________________
SMB-less as of 02/04/2012. Our savings account is richer, but our adventures are poorer.
BroncoHauler is offline   Reply With Quote
Old 04-09-2015, 07:46 PM   #4
Senior Member
 
shenrie's Avatar
 
Join Date: Nov 2012
Location: boise idaho
Posts: 2,281
Garage
Re: Death Wobble - Possible Resolution

whoa, that movement is crazy!

not familiar with boulder offroad. would you mind posting pix of your trailing arm setup?
__________________
"understeer is when you hit the wall with the front of your car, oversteer is when you hit the wall with the rear of your car, horsepower is how hard your car hits the wall, and torque is how far your car moves the wall."
shenrie is offline   Reply With Quote
Old 04-09-2015, 07:56 PM   #5
Senior Member
 
carringb's Avatar
 
Join Date: Jan 2009
Location: Corvallis, OR
Posts: 4,494
Re: Death Wobble - Possible Resolution

Looks like bad geometry on the radius arms. The must be absolutely parallel to the chassis and each other, otherwise they parallelogram and cause that motion. My suspicion is that the brackets bolted to the frame were stock F-series brackets (or maybe home-made) which don't adequately correct of the extra frame width of the E-series frame vs the F-series frame.

There is no reason you should need to add more caster to correct the motion. In fact, I won't think it will help. All of the other "fixes" like the steering ram and double-shear steering box are really just masking a geometry problem.
__________________
2000 E450 dually V10 wagon
carringb is offline   Reply With Quote
Old 04-09-2015, 08:54 PM   #6
Member
 
sidetrak06's Avatar
 
Join Date: Nov 2012
Location: Denver, CO
Posts: 55
Re: Death Wobble - Possible Resolution

carringb, that is a very good point. I will check the measurements of the radius arms and see how square everything is/isn't. Here are a few more pictures that I took while they were doing the 4x4 conversion a while back.









I believe the rear brackets weren't welded yet in these pics, just bolted. Anyone else want to chime in? The more the merrier! Thanks everyone.
sidetrak06 is offline   Reply With Quote
Old 04-09-2015, 08:57 PM   #7
Member
 
sidetrak06's Avatar
 
Join Date: Nov 2012
Location: Denver, CO
Posts: 55
Re: Death Wobble - Possible Resolution

Quote:
Originally Posted by BroncoHauler
FWIW, and I have no firsthand knowledge, but I've heard many times never to adjust the set screw on a steering box.


Herb
You can adjust the set screw, but typically in very small increments and usually only to compensate for small amounts of wear. I only adjusted mine 1/4 - 1/2 of a turn. It definitely makes a difference and can tighten up a fraction of an inch of slop that can be enough to get the wobble going.
sidetrak06 is offline   Reply With Quote
Old 04-09-2015, 10:31 PM   #8
Senior Member
 
carringb's Avatar
 
Join Date: Jan 2009
Location: Corvallis, OR
Posts: 4,494
Re: Death Wobble - Possible Resolution

Definitely some bad geometry there. Since the front of those radius arms mount to the stock axle mounts, the trailing end should be mounted a little inboard of the frame rails. Instead, they just built some off-set into those arms.

I think to really fix your problem, you will need to replace the current radius arms with OEM Ford F-series radius arms (the dog bone style, i.e. 2005_+) and some E-series specific brackets. Colorado Camper Van is the only outfit I'm aware of that sells them, since QuadVan will only install parts, not sell their parts ala cart.
__________________
2000 E450 dually V10 wagon
carringb is offline   Reply With Quote
Old 04-09-2015, 10:47 PM   #9
Member
 
sidetrak06's Avatar
 
Join Date: Nov 2012
Location: Denver, CO
Posts: 55
Re: Death Wobble - Possible Resolution

I have to think there is play in the radius arm bushings though, don't you? Looking at the end of video #3 the axle is perfectly flat and moving front to back. In my mind just picturing this, with a properly functioning tracking bar this type of movement could only happen with play in the system. What you're describing to me makes sense as the culprit that get this whole wobble set into motion. Or am I missing what your saying?
sidetrak06 is offline   Reply With Quote
Old 04-09-2015, 10:52 PM   #10
Member
 
sidetrak06's Avatar
 
Join Date: Nov 2012
Location: Denver, CO
Posts: 55
Re: Death Wobble - Possible Resolution

Boulder Offroad has done so many of these conversions I know this is not a common issue. Something unusual is happening with my particular van. Whether that is a geometrically improper setup or failed parts, I will find out soon enough.
__________________

sidetrak06 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not 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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

» Sportsmobile Registry

Hermes

Nimzero

Rosy

Isever
Add your Sportsmobile
Powered by vBadvanced CMPS v3.2.3
Disclaimer:

This website is not affiliated with or endorsed by Sportsmobile SIP or any of its affiliates. This is an independent, unofficial site.


All times are GMT -6. The time now is 11:47 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
×