I have not had the experience of the dreaded death wobble with my truck
primarily due to the fact it is a 2wd. However, I have read where a lot
of others with the 4wd have had the experience. The common problem
seems to be a worn trac bar. I have also heard of worn ball joints
contributing to the problem. Essentially any worn component in the
front end is a contributing factor. From what I have been able to
gather the real problem is a caster problem. Caster is what makes the
wheels want to return to the straight ahead position. Without enough
caster a wheel doesn’t want to return to the straight ahead position
and then you get a ‘fight’ between both tires. I have read that the
best caster settings are at the high side of factory specs (+5.5 to -6)
The big problem here is the alignment techs don’t understand what
causes things to happen so they don’t know what to change to correct a
given problem. Just because a unit is in specks doesn’t always fix
things. There are TWO things that will cause a DW. #1 Harmonic balance
of ft. wheels. #2 Caster setting.. Lets start with Harmonic balance.
There are TWO balance conditions of wheels . STATIC and HARMONIC.
Static is up and down bounce of the wheel. Harmonic is side to side
wobble. IF the harmonic balance of a wheel is OK but the static is off
by 5 oz and the wheel balance man fixes the static by hanging 5 oz wt.
on one side of wheel ,then he fixed the static but has caused a
harmonic imbalance. The wt. must be split and 2 1/2 oz be put on each
side of wheel to maintain the harmonic that was correct to start with.
Now most wheels will be off on both static and harmonic. That’s why you
see wt. opposite each other and spread around wheel. Now #2. Caster .
Caster is the imaginary line drawn up and down through the center of
the ball joints. If that line is exactly straight up and down you have
0 degree caster and 0 degree camber.
If that line leans to the outside on top 1 degree you have positive camber 1 degree.
If it leans in toward center of truck 1 degree you got negative camber 1 degree etc.
If line leans to the front on top 1 degree you got 1 degree negative CASTER
If it leans to the rear on top 1 degree you got 1 degree positive CASTER etc.
Positive caster will make the wheel want to turn towards center of
truck, negative caster will make the wheel want to turn out away from
truck. These caster settings should be within 1/2 degree of each other
to counter balance the pull of the other wheel. Think of a grocery cart
and the way the front wheels sometimes wobble. That is essentially what
is happening when the death wobble strikes. The front tires are
wobbling back and forth so violently that there have been reports of
the tires actually leaving the ground. As was mentioned earlier have
them set the caster to the top end of specks. Well you gotta know where
its set at now. If its at o degrees setting at top of specks will sure
change things. But what if its already set at top??
Another thing, just what speed does this wobble take place at.??
TOO much positive caster can cause a LOW speed wobble 10-15 mph. If you
got a wobble at 10-15 mph, and your wheels ARE balanced, Then find out
what the caster settings are and go 3-4 degrees negative, keeping them
within 1/2 degree of each other. with the right wheel being the more
positive . This gives you a hair left pull to compensate for road crown.
If you got a high speed wobble 35-40 up, then more positive caster will stabilize more.
Worn parts don’t cause the DW. Good stiff parts cover it up and resist
it. The front end really takes a beating when the wobble happens so you
will need to inspect ALL parts. If there is any wear found, it must be
fixed. Then try to find a good alignment shop.