Unstable Handling--Help needed

[Spang]

I've posted previously about my handling problems on my '05 DC, but after more observation and refinement of the symptoms, I'm going to try again in the hope that I might get additional suggestions/guidance.

The vehicle has 21,000 on it. For the first 18 or so, it was very solid and a pleasure to drive; pretty much what I expected after having put 60,000 on my 02 AC, which I traded in on the DC. Now, however, the DC has become a nightmare. It is very unstable at higher speeds. Any uneveness in pavement conditions (e.g., rutted pavement) makes it wander all over the road. Going laterally over transitions in pavement levels make it feel like you're driving on ball bearings. Even a modest headwind or crosswind likewise causes it to "float" back and forth in a very scary way.

I just returned from a long trip on the interstate, and I was afraid to drive it over about 60 due to this instability. I previously had the truck aligned on the Hunter, and, at least according to the print out given me by the shop, the positive caster is set at the high end of the Toyota specs, so I don't think that is the issue. I then took it to the dealer, and they are basically clueless, concluding that there is nothing wrong with the truck. (I live 65 miles away from the nearest interstate, so the tech who drove it I'm sure wasn't able to get it up to the speed necessary to really observe this problem).

So now I'm in a real quandry. I don't feel that the truck is safe to drive at highway speed in this condition, but my dealer, I'm quite sure, thinks I'm crazy. I'd really like to have the dealer go through every suspension component with a fine tooth comb, but I'm not technically schooled in things automotive, so I really don't even know what to ask them to look at.

Any suggestions about what to ask them to check would be GREATLY appreciated!

[wjdunn3]

Have you done any modifications such as lift, shocks, tires/wheels?

What tires does it have on it? What is the air pressure in each tire?

Are the shocks OK. A set of shocks that have gone bad can cause all kinds of weird handling issues.

Does it feel like the front end is wandering around, or the back end, or both?

[cleanb13]

The only thing that comes to mind is bad tires. I have had the same problem with the tires being the culprit. If the stock tires have over 20k miles on them, they probably need replacing anyway.

[DJ]

If it was fine for some thousands of miles and then changed radically, then something significant changed. The question is, what changed?

Given the symptoms you stated, one might first suspect that the alignment shifted. This can happen if you hit a pothole or if the nuts which tighten the alignment cams were not tightened properly. If that happened, the dead giveaway would be that your steering wheel would no longer be level when the vehicle rolls along in a straight line. So, is your steering wheel no longer level then? If it's not, then get the wheels aligned. If it is, then suspect something else.

You could have a tire that is experiencing tread separation, meaning the steel belted tread is separating from the carcass of the tire. The result is tread that squirms, especially at high speed, and variably in response to the road surface. If you're still using Tundra OEM tires, that's a real possibility. You can test this by swapping out your wheel/tire assemblies, one at a time, with your spare. If the problem goes away, you've found a bad tire.

[mitchinphx]

Tire would be my first suspicion. Alignment would be my second. Then steering tie-rod assemblies and the steering rack bushings...

also, the shocks (front & rear) are a good place to check but i'd be surprised they were bad at 21k unless they see a lot of washboard roads.

I'd also check to see if any spindle bolts came loose. there are 4 under each spindle.

[Spang]

I appreciate all of the suggestions; if nothing else, they reassure me that my logic is not totally out of line.

First off, the truck is stock; no lifts, shocks, or any other suspension related modifications. The only change from stock is tires; I'm currently running Toyo Open Country A/T, LT 265/75-16, with 34 psi in the rear; 32 in the front. The overall feeling is that the wandering seems to be more prounounced in the rear end.

Here's my attempted fixes so far. I too suspected tires right off. When the problem first manifested at about 18,000, my first response was to junk the stock Goodrich T/As and replace them with Toyo Open Country A/Ts, along with the aforementioned alignment on the Hunter. No dice. So, it seemed that the issue is not tires nor, assuming the alignment shop not totally incompetent, alignment.

Rack bushings seemed like the next "easy" fix, so I replaced the stock rubber bushings with urethane, along with another alignment. Strike two.

In response to DJ's suggestion, the wheel is level when moving in a straight line, so, again, alignment doesn't seem like the smoking gun.

Based on the suggestions so far, that leaves me with shocks and spindle bolts.

How should I go about checking these?

[ICON]

So the problem surfaced before new tires and replacing them didn't do anything? I rule out tires for the meantime if that's the case.

Since your mechanic knowledge is limited we really can't give much advice besides getting someone who knows about cars to take a real close look at it. If you take it to the dealer it's gonna cost an arm and a leg and from the sounds of it, it's gonna take a while to address each component. If you have a friend who knows cars, let him take a look. You really need a jack, or preferably a lift, to check each corner w/tires off the ground. From you description about the rear wanting to "push" it around as opposed to the front, it could be a bad rear leaf spring bushing or something else in the rear which has shifted the rear end to the point where it's not pushing it straight. However it very well could be something else entirely. The front end needs to gone through to ensure nothing's bent, broke, missing, worn, loose, or just wrong but you need someone who know what to look for how to check each component. I've never come across a vehicle w/bad shocks that resulted in such a severe handling issue. For example, for work i drive a '93 Blazer w/210K and a pretty good amount of play in the front-end components and it tracks very straight at highway speeds but when it's stationary i can move the steering wheel back and forth quite a bit. The shocks are also blown on it which just makes for a bouncy ride but nothing as severe as what you're experiencing. Sounds like something major has failed and needs addressing but what that is, is the question.

[mitchinphx]

have you tried driving sober?

[tempetom]

I bought a 76 Blazer from a guy up the street back in 1982. When I drove it down the road and hit a bad spot the front end acted like it was going everywhere. A friend (?) said all 4wds were that way. I got under it and the leaf spring ubolt nuts were loose. During the course of that happening, the bolt holding the leafs together sheared. I'm lucky it didn't kill me, but I fixed it. We don't have leafs on the front, but I'd sure check every suspension screw/nut and especially the spring hardware.

[BEU]

1. If cattycorner tires (left rear and right front or right rear and left front) are both low, the car will wander but drive in a straight line when you let go of the wheel. Check the cold pressure of all the tires. If the manufacturer recommends 35 psi, put 32 psi in it.

2. Go to the dealer and ask him to check the toe-in. Sometimes tire places don't give it any toe-in so the tires will last longer so I've heard. Toe-in gives it directional stability.

3. Buy a torque wrench. Take the wheels off and re-install them by tightening the nuts in a star pattern; first round 30 ft lbs, second round 60 ft lbs, third round 90 ft lbs, fourth round whatever the manufactuer recommends (ask the dealer). If you have six lug nuts, ask the dealer the pattern. Apparently mag wheels flex if not tightened correctly.

All of these have happened to me, except #2 which happened to a friend.

Good luck,
BEU