Bump Steer/Death Wobble issue after Alcan install

[goathearder]

Hey Guys,
I just installed a set of Alcans I bought this weekend on the front of my 73 and now I am having a crazy vibration issue on one particular bump. All I changed were the springs and I already have crossover steering. I have absolutely no issues at speed on the freeway or anywhere else but when I go over this one bump in the parking lot of my office I have the issue and its totally repeatable and never happened before.

If I am driving slow, the amplitude is less and the wobble/vibration seems to work itself out, the faster I got, the larger the amplitude gets and if I am going fast enough, it doesn't damp itself out until I come to a stop.

Balljoints are good, tie-rod is good, spring and shackle bushings are new, ubolts are torqued to 150 ft-lbs. I am not running a steering stabilizer but people say those are just band-aids anyway.

Now, what different about this bump then every other bump I go over is that its not perpendicular to the road, that is to say my tires don't pass over it at the same time. The passenger tire goes over first and then the drivers tire. That seems to be what is triggering it and that's the only time it happens.

Any ideas of what to check besides the stuff I already listed? Could the flexy springs be contributing?

 

[sreidmx]

Check caster..might need wedges to adjust it.

 

[goathearder]

Can do. What kind of angle should i be expecting?

 

[Babaganoosh]

6 or 7 degrees is what I hear is the ticket for our trucks.

 

[63chevyll]

That is the exact thing my 86 does as far as death wobble.

Only the perfect bump at right speed. After installing new springs and bushings and lift.

 

[goathearder]

Yea, its crazy to me that its so specific. I put a steering stabilizer in last night and no wobble on that bump this morning but I need to get an angle gauge this weekend and still check the caster.

 

[ryoken]

Mutt just developed similar... all new kingpins, x-over, etc a yr or so ago... it was fine, and just recently I noticed if I hit certain bumps at 20 to 25, it'll throw it into a bit of death wobble... if ya don't slow down that 5 mph, it'll start pounding.. all other speeds are fine, and no new parts...

I'm gonna try new 6" springs and see what happens first... the 4" ez rides seem to have worn pretty quick and I'd like a bit more height anyway..

maybe i'll try the washer trick, or just do hydro-assist down the road if it persists......

 

[Kay86K5]

or just do hydro-assist down the road if it persists......

This is the only real fix for it. I messed with death wobble for a while, tried new steering stabalizer, new d60 spring and busing kit from ORD, all of it. Decided to say screw it, and pieced together my own hydro assist for less than $300, and never had it again.

To the O.P., I am assuming you have a d60 (I didn't see anywhere where you specify what your front diff is). When you start putting larger tires on kingpin 60's, the axle truly is not designed to handle it. So it will always be there, however there are really good ways to mask it. That's where the ram of the hydro assist comes in. My brother has 37" MTR's on his K5 with normal crossover, and he has had death wobble for a while. We just finished the exact same hydro assist I did on his last night....and DW is gone

 

[goathearder]

This is the only real fix for it. I messed with death wobble for a while, tried new steering stabalizer, new d60 spring and busing kit from ORD, all of it. Decided to say screw it, and pieced together my own hydro assist for less than $300, and never had it again.

To the O.P., I am assuming you have a d60 (I didn't see anywhere where you specify what your front diff is). When you start putting larger tires on kingpin 60's, the axle truly is not designed to handle it. So it will always be there, however there are really good ways to mask it. That's where the ram of the hydro assist comes in. My brother has 37" MTR's on his K5 with normal crossover, and he has had death wobble for a while. We just finished the exact same hydro assist I did on his last night....and DW is gone

I'm actually D44 front with 35s still.

 

[sreidmx]

Death wobble is mainly because of something isn't tight worn or the caster is off.. Hydro assist is a bandaid.