Viscious Shimmy

[Wolfman]

Hey guys. I own a '99 sport Reg Cab, Short bed, 4X2, 80,000 miles, no mods and have picked up a very wicked shake.
It started back around Christams and only happened once in a while, I took it to my regular shop and they found nothing. Thinking it's probably a ball joint, or something like it, I figured it was still to tight for them to find and I'd drive it till it loosened up.
2 weeks ago I had the tires ballanced and rotated so there good to go. The shake has progressed to at least once a day so I took it back to the shop. Again everything checked out fine. They checked the all the joints, and bushings, wheel bearings, they even looked for cracks in the frame and arms.
The shaking usually starts when I hit a bump (somtimes a seam in the road will set it off) while turning (even slightly) to the right above 45mph. Driving straight or left it drivers fine, no shimmy in the steering or the rest of the truck, but when it starts shaking it shakes like hell and theres no warning.
The guy at the shop said the only other thing he could think of that might help is new shocks, but even that is a WAG (Wild A** Guess).
If any of you have had, seen, heard, or even made up this problem I would be GREATLY in your debt for any help you can be.

I know I don't post much but you guys have usually answered my questions before I need to ask them.

[boykjo]

I have a ford truck that did the same thing. How r ur brakes. R they high and hard. My brakes on one side would not release all the way. When I drove it I guess the rotor would heat up and caus it to grab on one side which made the front end shimmy visciously. I replaced the caliper and flexible brake line and it took care of the problem.
Just a thought, may want to look at ur brakes befor u go buying new shocks

[paratrooper]

The general rule of thumb is that if you feel the shake in the steering wheel, the problem is (obviously) in the steering or suspension parts. If you feel the shake in the seat of your truck, the problem is in the drive line. I hope this might help you zero in on the shake.

[Breakinstuff97]

check the p/s for air also. sometimes a small leak can allow air into the system and cause the steering wheel to shake especially when turning or over bumps. Ford explorers are notorious for this, turning the wheel when the engine isn't running sucks air right into the system through the fluid res. too.

[Sugarhead]

I have had a similar problem in my ram. I had a friend turn the wheel back and forth slightly while i looked at everything under the front end. turns out i had some play in the pitman arm. not where it connects to the steering box, but where it connects to the steering arm. I went and got a new one (heavy Duty) from Napa (-$80) and a pitman arm puller and changed it. Everything works great now. (Pulling a pitman arm sucks!!!) Look into it!

[Wolfman]

Thanks for all the help guys. I'll have to check all of that stuff. This is a great site for these type of questions.

[Htrod02]

I had the exact same thing happen to me while driving 75 and hit a bump on a bridge on the interstate, almost lost it. It did it a couple more times also. I checked everything and found a bad shock. Yes it was a fourwheel drive but I think the same thing could happen to a 2 wheel drive.