blazin svk

I have a 99 gs400 that is creeping up toward 160k. It has type flex coilovers and 20 inch staggered L-sportlines. The upper and lower control arms were replaced at around 120k when I got the car, ball joints included.

However, I have a decent shake at highway speeds. I could live with just the shake, but when brakes are lightly applied it turns into a death shake. More brakes= no shake. All of the shake is in the steering wheel and none in the pedal. All four rotors and pads have been replaced and to no avail. The bad shake only happens when tail gating someone and scrubbing speed or slowing down on an exit ramp. Like I said before, if you mash the brakes, no problem.

I am thinking that the caster bushings need replacement, but before I throw money at it, I wanted more opinions. When inspecting the bushings, they look fine, no rot or cracks and still soft. However, when using a pry bar it seems pretty easy to get the arm to move up and down at the bushing. Is this normal or should the arm be stiff at the mount/bushing?

Just to reiterate, the shake is not a vibration, but violent and scary. IT does not matter which wheels, but seems worse with bigger ones. I about to mount my gopro under the suspension and go for a ride to get a look at whats going on.

lexusls430

I have that same problem!! Light brakes and the steering wobbles, harder braking and its gone.

starfyrels

iTrader: (2)

Your rotors are warped if you tighten your lugs too tight. Also if your bearings are bad/shot you'll hear it and experience it while driving or braking. Get it checked out.

tiger4life

iTrader: (16)

Not sure what to tell you. My caster would be out of spec whenever i got an alignment. Replaced the entire arms (only way to get oem bushings) caster went back into spec. 2nd time they've been replaced, previous owner had them changed also. My bushings did not look bad when replaced. Easiest way to tell they are faulty is by the alignment specs. My highway steering wheel vibration decreased some, but i never had shaking under braking. I really would check the braking system including the calipers and rotors again. Sounds like they are the culrit.

blazin svk

I don't know about the other poster, but in my case, it is not rotor related. It was prevalent before and after a complete rotor swap. I am also quite familiar with wheel bearing problems. There is no noise, and bad wheel bearings would not transfer the shake into the steering wheel. WHen the bearing is bad, the hub and out is what is shaking. THe spindle would still be static, which I don't believe that it is in my case. For the amount of movement in the steering wheel during the bad shake, I suspect that the whole assembly is moving.

Ok, so I wasn't completely honest. This is far from my first rodeo, but I don't recall ever having a bad bushing in an control arm that is attached in this way and angle. What I want to know is what direction of movement would be transferred into the suspension while lightly braking, if a caster bushing was bad on these specific cars.

blazin svk

I don't disagree. I am not convinced that this much shaking is coming from bad caster bushings. The only other thought that I have is that there is air in the front brake system. WHen I purchased the car, the fluid was below the fill line. This was due to worn out pads. I replaced the pads and bled the system. I have tried to rebleed to check for air, but have not got any to come out on multiple attempts.

The one thing that keeps me leaving the thoughts of brakes is that the shake is amplified with larger wheels. That makes me go back to suspension due to leverage forces.

Nobody303

I just did caster bushings over the weekend. My symptoms were the car being all over the place when changing lanes on the highway as well as a considerable shaking at highway speeds. Got the carson caster bushings, the shaking is completely gone, but it still pulls a bit when changing lanes.

starfyrels

iTrader: (2)

p/n of the bushings?

TonyN

iTrader: (1)

I have the exact same problem, seem like when im at speed and I dont let the suspension settle after making a lane change or something the steering wheel will shake with light pressure on the brakes, increase the brake pressure and it goes away or if i coast a bit and let the suspension settle it will not do it at all. I am thinking my caster arm bushing also, it is not the brakes I suspect because I do not feel pulsation in the pedal. anyone else have this problem and found a fix?

blazin svk

Bump for some exposure

nezlyfe

I replaced the upper, lower arms, LBJ, tie rods, sway links which helped A LOT when this happened to me but I still have slight shaking in the steering wheel and none on the brake pedal and the same symptoms as everyone else. I just ordered 4 new rotors and hopefully that'll get rid of the shaking completely. If you want to make sure its not your rotors jack each corner up one at a time and try to spin the wheel if its free then you're probably good but if it sticks with no brake applied or it gets stuck on one while spinning then ya your rotors are warped

Acidic

iTrader: (1)

Pull it all apart and inspect it... jack up the wheels and move them around rather than postulating about how you think the suspension works. I find that if I don't troubleshoot I almost always buy the wrong part... Don't forget to give the engine mounts a good look too.... There is a procedure in the manual on how to check the whole suspension...