Death Wobble on New SAS rig

Thanatos · Jul 16, 2007

I just finished the SAS on my truck. Took if for a test drive and at 30 mph there is an awful shaking of the front end. I looked out the window and the wheels were shaking left/right really bad. I am running an 80 Toyota axle on 89-90+ rears up front/new wheel bearings and seals/T-G Histeer/M-C front hanger 1.75" forward and M-C shackles. Got a couple of replies on Pirate (http://www.pirate4x4.com/forum/showthread.php?t=597401), but not sure where to go with this. Do I rotate the knuckles or add a shim? My 87 SAS rig is running RUF's with a shim and does not shake like this. :wtf:

skrause · Jul 16, 2007

What is your caster at now?

I love how those idjits suggest things like hydro assist.

iceman1 · Jul 16, 2007

check your alignment.a had a wobble so I toed it in a bit.now it works fine.you might at least give it a try...

tj40ounce · Jul 16, 2007

skrause said:
What is your caster at now?

I love how those idjits suggest things like hydro assist.

X2... I had to move my steering box forward when running rears up front. Not sure if that would cause the DW, but may be something to look at.

84Toyota4x4 · Jul 16, 2007

Just after adding hysteer and rebuilding my front axle, I had a NASTY wobble in the front like you described when I took it out to make sure I got the brakes bleed all the way.

I knew I hadnt set the toe yet, but I forgot that I left the lock nuts for the tie rod and drag link loose so I could adjust them. I ran it back home, tightened them, and the wobble was substantially reduced. After I was sure the brakes were working, I took it back, set the toe, tightened everything down, and the wobble was gone. So, if it were me, I would check the toe.

Also, did you rebuild the axle? Are you sure you got the knuckle preload right? That could cause some nasty wobbling if thats not right. Oh, and are the wheel bearings tight?

~T.J.

Rix · Jul 16, 2007

castor castor castor
when you rotate the axle for better pinion angle, you mess up the castor.

SACD_Runner · Jul 16, 2007

Rix said:
castor castor castor
when you rotate the axle for better pinion angle, you mess up the castor.

exactly the reason why mine isn't clocked. Leave it normal and buy a double cv shaft and call it good.

skrause · Jul 16, 2007

SACD_Runner said:
exactly the reason why mine isn't clocked. Leave it normal and buy a double cv shaft and call it good.

x2. Castor before pinion. It's the front axle, if you need 4wd on the road you shouldn't be going fast anyways.

Thanatos · Jul 16, 2007

skrause said:
What is your caster at now?

I love how those idjits suggest things like hydro assist.

How do I check the caster?

tj40ounce · Jul 16, 2007

seafarinman said:
How do I check the caster?

meausure off the hi-steer arm....

Thanatos · Jul 16, 2007

Okay I measure off the hi-steer arm in relation to ?? I called Randy's Offroad and they told me that I should cut my spring perches off and rotate the axle and weld new ones on.... OR use shims. I am going to get some 6 degree shims today. I hope that will help. The rig looks really pretty on the driveway but I would rather get it on the road.:awesomework:

tj40ounce · Jul 16, 2007

seafarinman said:
Okay I measure off the hi-steer arm in relation to ?? I called Randy's Offroad and they told me that I should cut my spring perches off and rotate the axle and weld new ones on.... OR use shims. I am going to get some 6 degree shims today. I hope that will help. The rig looks really pretty on the driveway but I would rather get it on the road.:awesomework:

or shorten/lengthen your rear shackels maybe.

http://www.4crawler.com/4x4/4R_TechInfo.shtml#Steering

from pirate

But from my conversations with tire alignment guys, is that it should be around 5-7 degrees for your typical solid axle application with large offroad tires. the reason why they feel the axle was set up real vertical is to decrease the force it takes to steer since lots of the trucks came with manual steering. Hence I recommend 5-7 degrees.

skrause · Jul 16, 2007

Check in relation flat, or to the bottom of the frame rail if you can't get the truck totally level. You're looking for around 5-8 degrees or so leaning back like the front fork of a bicycle. On toe-in, a quarter inch in on the front measured at the tread should be fine. I just put the front up on stands, mark the tread and measure, spin and measure again using same marks.

tj40ounce · Jul 16, 2007

measur the caster by using a degree angle finder on the top of the steering arm and by the bottom of the knuckle king pin.

Hip · Jul 16, 2007

castor MUST be between 5 to 7 deg first....

then check toe in. i set mine at 1/16" toe in.

if your castor measures right and toe in is at least somewhat toed in. then look at all steering components...TREs stuff like that everything should be tight not sloppy. might need a friend to turn the wheels back and forth as you look feel measure stuff. your leaf spring hangers and bushings should not be sloppy either. make sure all the bolts are tight.

Dain Bramage · Jul 16, 2007

i had a bad wobble start a couple weeks after i did my SAS, turns out my shackle bolts were a little loose, i tightened them up, and it really quieted it down.

johnboy1 · Jul 16, 2007

i have the wicked DW around 30 too, but im running 36 Iroks. and i still have the stock Tie-rod. i always thought that the dw was from the TRE's going out. but yours are new.

Mudmayhem101 · Jul 16, 2007

caster/pinion

There is a better solution for the problem which is what i did grind away the factory welds and rotate the housing up. then adjust your caster and reweld it together, takes work but works great.

darius · Jul 17, 2007

Hip said:
castor MUST be between 5 to 7 deg first....

then check toe in. i set mine at 1/16" toe in.

if your castor measures right and toe in is at least somewhat toed in. then look at all steering components...TREs stuff like that everything should be tight not sloppy. might need a friend to turn the wheels back and forth as you look feel measure stuff. your leaf spring hangers and bushings should not be sloppy either. make sure all the bolts are tight.

Actually to my knowledge toyota front housing's are set at right around 0 degrees caster factory, I know for a fact cruiser's are set at + 1 degree on the driver's side and - 1 degree on the passenger side for road crown, and I believe pickup's are similar as far as not having the knuckles rolled too far back. 7 degrees is a long way's to roll the knuckles back with you're toyota housing I would shoot for about 4 degrees.

skrause · Jul 17, 2007

darius said:
Actually to my knowledge toyota front housing's are set at right around 0 degrees caster factory, I know for a fact cruiser's are set at + 1 degree on the driver's side and - 1 degree on the passenger side for road crown, and I believe pickup's are similar as far as not having the knuckles rolled too far back. 7 degrees is a long way's to roll the knuckles back with you're toyota housing I would shoot for about 4 degrees.

Crazy. When I set mine they both measured out exactly the same using a digital level, '85 minitruck housing though. :eeek: I don't have my manuals handy but I swear the stock setting was 5 degrees.