My 1992 4runner I just bought is pretty unstable at highway speeds. It seems to want to track every rut and ridge. It feels like it is mostly the rear end is doing it. The steering is tight and does not feel weird. The problem got worse when I installed OME coils and 31" tires. My 89 felt nothing like this and it had more miles.

Is there anything in the rear suspension I should check? Are there bushings to wear out? Is there anything in the rear suspension that can be aligned?

Maybe the front toe or caster is way off and is not tracking well?

 

maybe the rear swaybar? beyond that all i can say r shocks or maybe its a tweaked frame..... good luck in finding the problem

 

The shocks are definitely soft, that is on my list, but it feels more like a side to side motion, than a rocking. Could be related though.

 

describe the motion.... body roll? and how are the tires?

 

Tires are okay, stock like Goodyear wranglers (can't remember model name, came on the rims I installed when I bought the truck) with 30-40% or so.

It feels more like the rear end wants to go a different direction from the front, not really a roll motion. It really feels like the rear end is shifting back and forth. I will get under there this weekend and pry around. Visually it looks okay.

Is it bad to have the swaybar hooked up like stock with 1.5" lift coils? Do I need drop links on the sways or the panhard bar? Maybe the stock length shocks are topping out? It seems like they still had a couple inches of travel.

 

sadly, im not the guy to ask about lifts. id try replacing your shocks if they need it, and replacing the tires, if possible. whats the DOT number of the tires? the last 4 numbers.. should look like 4607 or 5605 or something.. those numbers are as follows: first 2: the week of the year the tire was made, the last 2: the year the tire was made. if the last 2 are 03 or older, id replace them. if there are only 3 numbers, like 057, or 980, then DEF. replace them. it kind of sounds like the tires, which is why i want to know how old they are..

 

well i have 31'' tires

does it feel like if you ride an atv in the sand. when you turn its like the back pulls the tires and your almost at a drift (not straight)?

 

How high is your rear lift?

Keep in mind, the higher you go, the more your panhard will need to drop. If you don't, it shifts the axle over towards the pass side, making your truck drive untrue. Its usually not a problem below 2".

 

4B72 and 4500 are the numbers near the DOT.

Maybe the pressure is too high, I am running 35psi, which is what I always ran in my old truck with true 31's on it. These tires are actually 265/70/16.

Lift is 1.5", OME 900 springs, but it was sagged pretty bad, probably 3-4" lift over what it was.

I am leaning towards tires too. Everything seems pretty solid back there.

 

The swaybars are fine with your lift. Did you alter the front suspension when you lifted the rear?

Is there any uneven wear on the tires? Typically, what you describe is very indicative of too much toe out. Now too much toe in can do it too, but it takes a lot of toe in as that condition is a stable equilibrium where the toe out is an unstable equilibrium.

Other things can cause erratic behavior like a worn idler arm or wheel bearings.

First though, tell us how the tires are wearing, that will help a lot.

Frank

 

the LAST number, farthest away from the DOT, ends in 00? id replace them... if thats what it is, then those tires are from 2000. almost 8 years old. im not sure about where you are, but in vegas, tires dry rot at 4 years old. at my work we;ve replaced tires with almost perfect tread but LOTS of dryrot. same with san diego, except they can go a bit longer. the useful life of the tire usually is 4-6 years.

 

Tires are worn pretty even, I have only had them on a few weeks, so not sure how my truck is wearing them.

I cranked the T-bars a bit, still have about 3/8" left of droop on the bump stops.

Even though it does not feel like the front, I will check out the steering box slop and idler arm this weekend. Wheel bearings up front feel good and were packed relatively recently by Toyota (previous owner).

 

Unless the back tires are way low it's the front end. You just feel the top heavy rear end swaying side to side.

If you adjusted the t-bars upwards you have toe in as well as camber in which will do funny things.

Check out www.sdori.com, there are instructions on how to adjust the alignment.

Frank

 

I'd start with a good alignment and a front end inspection as well...

 

I had this same problem in my CJ when putting new 16" tires on one winter for plowing when I lived in CO. It felt like the rear end was skating or wagging all over even on dry roads.
While all vehicles have this if you wag the wheel, this was severe and sounds like what you are describing.
It was totally the fault of the tires. They were good tires, rated right, but had terrible sidewall flex.
I ended up getting rid of them and the problem went away.

 

Well, the problem is getting better, I tightened the steering box and replaced the idler arm bushings. I am going to take it in for an alignment and see if that fixes it the rest of the way.

 

Well the problem is pretty much solved now: new idler arm bushings, tight steering box and an alignemnt later it drives much better. Toyota had done the previous alignment during the relay rod recall last year (previous owner). I took it to my regular well respected small shop, they said the caster was WAY off, only a few tenth's of a degree, instead of 1.5deg or something. That seems to have been the root of the problem. I wonder if Toyota even bothered to check the caster?