I have a 2000 SR5 with a shimmy that occurs at highway speeds. Here's my details if it helps the experts:

1. The tires have about 5-8k left in them and are high quality Michelins, but they do show a bit of uneven patterned cupping on the interior edges which would normally expose the issue of 'not rotating and balancing often enough', but in my case, that isn't the case.

2. The shimmy is between 60 and 72 mph and mostly dissipates above 70.

3. The shake seems to be in the steering only. It makes the vehicle seem quite unsafe at highway speeds, especially for my wife.

4. The local experts I've had give it an exam state that the front shocks and wheel bearings are the combined culprit. Possible correlation: I do feel a loss of road connection tough a vibration/bounce (if that's a good way to describe it) when traveling 30-50 mph and hitting uneven road surfaces (breaks, potholes, edges, etc.).

But I'm wanting a better opinion prior to going the change one part after another route...

Thanks in advance for feedback!!

Bounce the front suspension, when you let go, if it continues to bounce for more than a second or 2, your shocks probably are bad. But, your worn tires might very well be causing most of the issue. If the shocks seem blown, I'd replace those before doing wheel bearings. Usually bearings will make a whining/grinding noise when they go out.

Thanks for the input! The bounce after a hard 'push down' is very minimal. I'd say that it returns up and goes down maybe 1/3 the distance then returns up.

As far as bearings go, there is no overly apparent grinding or whining when driving. I've had a bearing go in a VW Golf and it was very apparent in its sound. This 4R is relatively quite as far as I can tell.

What about play in the wheel when suspended? The local expert who told me shocks and wheel bearings stated that there was a little play in the front wheels and that is what exposed him to the bearing issue; but, of course, he's in the business of selling parts/service.

If these are OK, could the tires really cause such a shimmy at highway speeds and loss of road connection after bumps? I never would have figured, but I'm a new 4R owner. It does need a new set in another 5k or so.

Again, Thanks!!

I know my 4runner and my taco both have a little play when the front wheels are suspended (and they always have). So I would venture to say some play is normal.

I've had lots of tires cause vibrations between certain speeds as they get close to wearing out. They get out of balance, especially if they are cupping/not wearing evenly.

The loss of road connection after bumps sounds more like a loose steering rack, worn tie rod ends, possibly worn ball joints, and I would check the sway bar end links and bushings as well. You can check the steering rack by bending down on one knee so you can see the rack under the truck. With the drivers door open (and the motor running), reach up and rock the steering wheel back and forth a few inches. If the steering rack itself moves at all, your rack bushings are toast. It's about $20-25 for a new rack bushing kit, but the labor takes a couple hours.

You were dead on your last diagnosis idea; I checked the rack and there was very noticeable play between it and the frame, so I'm going to find a rack bushing kit and replace them as my step one to smooth travel. BTW, what supplier do you recommend? And, due to your experience, do you have any pointers that ease the replacement?

Thanks!!!

I got my rack bushing kit from wheelersoffroad.com, I think it was $20 + shipping. I got the poly bushings (Energy Suspension brand I think). It's not that hard to r&r the bushings, but you'll need a few big sockets (a 19mm and I think the biggest one is a 24mm IIRC). The hardest part on mine was just getting some of those bolts loose because you don't get a lot of leverage with a breaker bar between the rack and the ground. If you have access to a car lift, it will make the job easier. But it can be done on the ground.

You might as well replace the rack guide while you're at it. Check out this thread..
How to: Replace steering rack guide- Pictures