Here's the background; about 6 months ago I briefly noticed a minor side to side sway/wobble in the rear end of my 4runner while driving from Grand Rapids, MI to chicago. Speed was approximately 70 mph. I had my wife, my 3 year old, and a dismantled bowflex onboard. It wasn't violent or extreme, just enough to make me straighten up in my seat and wonder what it was.

Fast forward to two weeks ago, I was doing a 3.5 hour road trip with a mountain bike and Thule cargo box mounted off-center on the roof, a 2 bike hitch rack on the back, and a rear end full of run of the mill family vacation gear. 15 minutes into the trip (about the first time I hit open freeway) the wobble showed itself again. Roughly one back and forth float/sway per second. Significant enough that the view in my rearview was like a drunk trying to take a picture with a digital camera. Once I got where we were going, I offloaded all the gear, centered the cargo box on the roof, dumped the bike tray and trailer rack and went for a drive. Greatly reduced, but still potentially present (may have be psychological, though). On the way home, I kept the box centered and braced up the hitch rack with ratchet straps to keep their swaying to a minimum, in case they were adding to the momentum of the sway. I took a lot of care in evenly distributing weight throught the back, and kept heavy stuff out of the cargo box. The sway was actually worse, kicking in at 62 and above.

On some stretches of road it woud disappear for miles, and other times it would ramp up and keep going for 15-20 back and forth cycles. Abrupt acceleration and breaking would interrupt the sway. Weather patterns were not extreme, no heavy winds, no rain or anything like that.

From the car guys I know and have spoken to in person, I've heard cupped tires and sway bar bushings.

The truck is a 2000 limited on stock size Destination LE tires, not religiously rotated, on a 1 year old Toytec ULK. Recently replaced rear brake shoes and greased the drive shaft fittings.


Any similar experiences or other suggestions out there before I start throwing tires and parts at this thing?

 

I would do a 4 wheel alingment to start. If it has other problems the tech doing it should see them.

 

i do have lifetime alignment, but haven't put it to use in about 6 months. Good call. Needs new tires, anyway. Maybe I'll do both this weekend and see if that resolves it. I like the idea of the tech spotting issues while he's in there.

 

15 year old truck.
What suspension bushings have been replaced over the years?

 

Have you checked your shocks?

 

I've owned it since 2009, I've replaced both front sway bar end links, one LCA, and did the suspension lift. That is the only work I know of that has involved any bushings.

 

Only by pushing down on the corners, the rebound seems fine. No leaks. I haven't done any removal for inspection.

 

My wife used to have an old Bronco II. And it had a set of Wrangler tires on it. I think the tires had a bit of sidewall flex, but if I drove it on the highway for a while, I would get into a sort of subconscious feedback loop with the tires, and start doing the same thing. The Bronco would squirm a little, I'd instinctively counter steer, it would counter squirm, I'd counter steer, etc, etc. I could stop myself from making the tiny corrections if I tried, but it kept firing off an instinctive urge to correct that I couldn't suppress for long.

Net effect seemed pretty similar to what you're describing, the car would do slow oscillations that had some vague relationship to the road, but which were mainly related to the tires and my reactions to them.

Those flimsy feeling Wranglers were replaced with some Michelin LTX's and the thing drove straight as an arrow.

So I might suggest checking the tire pressures, and even if the rear's aren't low, perhaps staggering the tire pressure a bit and having 4 - 6 psi more in the back than in the front. Thus moving the sidewall flex balance up to the front.

 

I think quite a few things caused this.

Does it have this issue every time you drive it ??

Same speeds on county roads??

Just the interstate??

This is Michigan I think the minor vehicle issues and the wagon tracks were what caused your problem

 

Hi Ruckus-
2 things I would have checked out.....is the rear axle tracking straight ahead? An alignment would verify that. Also, is the panhard rod loose or wobbly?(tracking arm oriented in the dame direction as the axle housing). Is the related weld cracked at the axle housing?

 

The panhard has a little play in it. The tire shop just called and said I've got tie rod issues. 2 out of the 4. Had one done last year when I did the lift. Another $500, we'll see!

 

Have you fixed the problem since last post? I had exactly same problem. 70 mph driving alone; more weight, more violent and at lower speeds. Pulling trailer- 40 mph. Changed the bushings in the rear lower control arms. Problem solved. Went withToyota parts, but you can find cheaper online. PITA to press out. Easier to just buy new control arms, but more money.

 

^He should be right, Rear control arm bushings are the culprit. Experienced this myself, GL!

 

Haven't nailed it down yet, but did seem to find improvement by tightening down the rear torsion bar, but it still shows itself when there is ANY weight in the back, especially an irregular load. Just bought a new daily driver, so I'm under less pressure to get the issue figured out. I'll look at the rear LCAs next, thanks for the input guys!