I've had my sas'd 95 4runner on 37's for about 2 years, only about 10,000 kms on the sas as its a weekend warrior. It has always had a wandering steering issue, and im at the point where im completely out of ideas on the cause. It is not bump steer, it just does not want to go down the road straight and I find im always making slight corrections. It will be traveling straight, and then just start to head off course slightly, in either direction. It isnt sudden, just a gradual "now im going left a little" and its easily corrected but its constant and annoying.

So you're thinking castor, which is the conclusion I came to after tons of researching. I have my axle mounted forward on the leaf springs, using the rear hole in the spring pad. This gains me a little castor since the leaf springs are in a "U" shape, but I've still gone ahead and installed castor shims in hopes to improve things (pointing the pinion down, giving the knuckles/tires more "heel") and I have not noticed any difference in its behavior. Is it possible I need more castor yet? I find that hard to believe but right now I am out of ideas.

I have also tried tightening the steering box with the adjustments on the top, tried using my castor shims in the opposite direction (pointing the pinion up) and going from 1/8" toe in to 1/4" toe in. All my balljoints are tight, the ujoints on the steering box are tight. All the bolts that hold the leaf spring to the truck are tight, but not too tight to cause binding, and the ubolts are also tight.

I am running trunion eliminators in the truck which is where Im possibly headed next in hopes to tighten things up with less shimming, or I might try swapping out my steering box to see if that makes a difference.

If anyone has any other ideas on what my issue could be I would be grateful for the insight, im at the point where im willing to try about anything.

 

Do you have a steering stabilizer? Have you considered maybe your steering might be a little too tight? If you bump the steering wheel to the left and let go does it continue to pull left until you bump it a little to the right then it pulls right? Are you judging this when driving on good paved roads? You might consider intentionally creating a pull to the right by lowering the pressure in the right front tire and see if you still get the wandering effect or if it just pulls right. Have you checked to see if the rear end is bolted in tight and the spring eye bushings are good?

 

I do have a stabilizer installed, its installed correctly so it does not limit my steering either way. All bushings on all leaf springs are good, bolts are tight. Having the steering set too tight could be my issue for sure, if I give it a little bump to the right I have to correct it or it continues on right. My trunion eliminators possibly clamped down to hard?

 

"My trunion eliminators possibly clamped down to hard? "
Could be, it could also be that you tightened the steering box too much (or it was already too tight), I would suggest disconnecting your tie rods at the knuckle and turn them by hand to see if they are hard to turn or not. pull the steering stabilizer and try driving without it. Maybe loosen the steering box a little, I'm not sure what the proper spec is for adjusting it, but there is supposed to be slight play in the input shaft (rotational not side to side).

 

The box is marked to be put back to where it was, I just never did because it didnt get any worse or better. I actually have tried without the stabilizer installed and it makes no difference. I remember when I installed the trunion eliminators that there was a break free spec where you hook your fish pull scale onto the steering arm or the caliper mount or something and pull and see what the inch lbs to make it move is, and I remember being within that spec ( I had the instructions infront of me when I installed it) but like I mentioned im at a loss now, so I might swap in my spare steering box and tear apart my knuckles to double check the shimming and preload. I cant for the life of me figure out what else it could be.

 

You make no mention of what your actual castor angle is, and without knowing the exact castor measurement you are chasing your tail. Get a measurement and report back, it should be 6° IIRC.

 

I can see if I can get my angle finder somewhere on the steering arm to get an exact measurement, I can easily get what the angle is at the perches (stock) if anyone knows the relation from perch to knuckle. I remember 4crawler had a write up that said the perch itself should be at 4 degrees (I think), I'll google it when I'm home, as well as report back with my measurements. I'm fairly confident my specs are within range as I remember going through all this when I started this debacle. Will report back though.

 

I had the same issue, and I swore I set my system up(links not leaves) correctly. The alignment guy even told me it was correct, but driving was another story. Took it home and had to add a few more degrees to stop the wandering.

 

Was that on a yota axle? My castor is set to 9 degrees on the driver and 8.5 on the passenger, with my shims installed the correct direction making the pinion point down.

 

Yes it was when I SAS'd my 88. And yes the pinion would point down.
Possible issues some have been mentioned...
Steering box too tight.
Knuckle bearing caps too tight
Check the u-bolts are torqued properly