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Death Wobble on new SAS rig

4K views 36 replies 22 participants last post by  seafarinman 
#1 ·
Just finished my SAS (well except for moving my steering box forward and making a square driveshaft) and I took it for a test drive, and around 30mph I get this godawful shaking up front that would not stop until I stopped. I turned around and went back home. I took off the wheels and verified that the wheel bearings were tight and intact, and that the wheel spacers were in fact tight. I had set the toe in at 1/4" closer in the front of the wheels. I did not yet set the steering stops though. I remember reading somewhere about caster angle. Could that be the cause? I am running an 8 leaf pack with 2nd gen/3rd gen rears up front with a rear add a leaf. I was looking at my 87 SAS truck and it has a shim up front and does not have the death wobble. I don't have my steering stabilizer mounted up yet. Any ideas?:confused:
 
#4 · (Edited)
I actually broke open the pack of your old springs to use the leaves. (I am running 7 Toyota rear leaves and a 1.5" AAL in the front and 11 Toyota/Mazda leaves in the rear + overload). One of the problems that I had was that the front eye of the rear springs had the factory Toyota bushing in it, and the hole in the bushing sleeve was too small for the MC front hanger bolt to go through. So I ended up burning out the bushing and ended up using a Mazda rear spring bushing that had a larger hole in it. I think that it was too loose. Anyone have a part number for a correct bushing that would go in and still allow a snug fit with the MC hanger bolt? If the fix is that easy...:shaking:
 
#7 ·
(I am running 7 Toyota rear leaves and a 1.5" AAL in the front and 11 Toyota/Mazda leaves in the rear + overload).
11 leaf rear pack? :eek: They must have angry flex.

Please tell me that's a typo.
 
#6 ·
i saw this on 4x4 wire

http://www.4x4wire.com/toyota/tech/rotated_housing/

he was doing it for better pinion angle but you can also correct your castor.

i have the same issue and i have replaced,bearings, bushings, ballanced tires and i even went as far as have the tires trued at the local truck stop, still had the same death wobble. i have narrowed it down to the castor angle. im going to use the trick in that link to correct my castor angle. roger (4 crawler) seems to think castor is my problem too.
 
#13 ·
CASTER & TOE-IN.........CASTER & TOE-IN...... Had the same prob & you need at least 7 deg of neg caster. Check the entire front end for loose bolts, worn bushings & re-balance your tires ect...BTW that rear leaf pack CRAZY! :eek: Loose about half of the leafs & the load leaf! Unless your going to carry some heavy shit in the back.. DW sucks
 
#14 · (Edited)
Well unless I lose some leaves and substitute some blocks I am going to have some major 4Runner style ass-sag. (edit:The reason that my rig is so high up front has to do with the fact that my tierod/draglink/pitman were hitting at compression with 6 leaves 3 Toyota/3Mazda I swapped it out for 6 toyota leaves and a 1.5" AAL. I still need to move the box forward. Then there was the oilpan/axle clearance issue.) How do I get the 7 degrees of negative caster? with shims? I will go get them today if I know how many degrees of shim I need. :confused:
 
#16 ·
what tires are you running as well?? Are they new or used?? I bought a used set of tsl SX's and they sucked. If they are bias plys that could be part of the problem. I had to mix and match my tires around 3 different times to find out which ones will work best up front, due to balancing issues. But I did figure it out. Just something I'd try, it worked for me. New tires shouldn't be such a problem. Just get them balanced if you haven't already yet.Good luck.
 
#21 ·
This might sound stupid, but are your lockouts truly unlocking?

Could the vibration be from the square driveshaft? I have had problems with the yokes not being completely centered in the square tubing. If your lockouts arn't allowing you to freewheel the shaft might still be spinning.

I would pull the front shaft out and test drive it again to eliminate this from the equation. Just a guess before starting to tear into everything and working on you Castor angles.
 
#24 ·
The stabilizer will mask the real problem, better to get it as good as can be before installing the stabilizer. Porterwagner might be onto something with the tires, bias-plys will magnify any other issues and cause some of their own. Definently check the caster angle to eliminate that possibility.
 
#27 · (Edited)
Well here is an update. I checked everything and my toe-in. I have the toe-in set at 1/4". I installed a 6 degree shim under the front spring pack, and removed a leaf so that I could get the stupid u-bolt flip back on. Also checked the steering arms for tightness with a torque wrench. Checked the wheel spacers and wheels as well. Took it for a test drive and it was doing good, then all of a sudden, death wobble again. Slowed down and drove home again over 50mph and no more death wobble. I think that my front spring bushings are kinda loose. got new ones in the rear eyes of the springs though. Anyone know where to get new front spring bushings for 89 4Runner rears? These are the bigger bushings with the metal tube inside that is too small for the 18mm front hanger bolt to go through. I ended up burning out the original bushings and using some mazda rear spring bushings from some springs that I chopped up. Thanks for all the ideas guys. I just need to install my bumpstops and make a driveshaft and I can actually test the 4WD. I will post more results when that is complete.

*edit* I am running the same Pro Comp Mud Terrains (31x12.5x15) that it was running as an IFS rig. They are about 40% tread left and I am not going to get new tires until I regear the thirds. I am planning on going to 5.29's and to run some 35-36" rubber when appropriate.
 
#29 ·
I think that is a great idea. My buddy did his SAS at the same time that I did mine, but he didn't rebuild his axle at all. He has driven his yesterday and today and he is not having any problems so far. I am going to get him to put my wheels on his rig and get them balanced at the local walmart since he has lifetime balancing on his wheels.
 
#30 ·
Marlin has those bushings you need. Be careful though. One "pair" is a left and right half that is effectively one spring bushing. You will need to order two so that you get two spring bushings. I made the mistake of not doing that and ended up paying $8 in shipping for a $2 item twice :doh:

I would also try decreasing your toe just a hair. I know it sounds weird, but an 1/8" can make a big difference. My old truck was really sensitive to toe, and anything more than 1/8" would make it buck like crazy.
 
#32 ·
I'm having the same problem after moving my rear springs up front. i don't have my torque rod on yet, need to cut it about 2" to compensate for my axle being moved forward, Everything is tight on there... could it be that the wobble is being caused by the torque rod not being there?
 
#33 ·
Well I just checked everything again, and I reset my toe to 0 and took it for a test drive and it seems to be good so far. I am going to fab up the mount for my steering stabilizer and make the bumpstop landing spots and weld in the old factory bumpstops. The truck is driveable on the road at this point, but I still need to move the box forward for the trail... but since this rig is not seeing the trail for a few more months, I am not in a hurry to move the box. Anyone know if it can be safely moved without disconnecting the hoses? :D
 
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