Shaking at 55+, rack/pinion?

[Black01Vert]

My 03 GT has had a pretty bad shaking problem at speeds above 55. It seems to be coming from the steering/front end, I thought it was out of balance/bad tires at first until I just recently put on new tires. It shakes just a bit less, but it's definitely still there. The "mechanic" at pepboys first said my passenger outer tie for was about to go soon but it was still good before attempting to align it. Then he goes to tell me that I need a new rack/pinion because there was some play in there.

He tried showing me but I couldn't see this "play in the rack" he was describing. After this I ask if he could at least adjust the caster/camber and says no because he needs to put on a new bolt. He points to the strut bolt on the bottom of the strut, next to the tire. I tell him the adjustments are made at the top, in the engine bay.. He says no?!

I have j&m caster camber plates btw. Can bad rack and pinion cause a shake at highway speeds or is this guy full of it. Pepboys was about to close so I think he just wanted to get out of there.

There's no play in ball joints/tie rods, wheels are balanced(does this with my stock wheels as well), struts seemed good when I installed cc plates, toe was adjusted a little while ago..

What can possibly cause the shaking? Steering wheel moves side to side at 55+ and the whole car shakes.

 

[tropicmustang]

Does this occur with different sets of wheels and tires also? I am the Head Brake and alignment Tech at a Les Schwab in California. First off it dosen't make sense why the tech told you the rack is bad, are the seals leaking? Inner and outer tie rods can be replaced without a sweat. For those parts to cause a shake They would have to have a significant amount of play in them. Its not very common for something like that to cause a problem like this. It honestly could be multiple things. You could have a bad tire.. I would have the tires road force balanced to make sure you don't have a bent wheel or even a bad tire Its hard to diagnose something like this without seeing the car. It could even be something else such as a motor mount etc...

 

[Black01Vert]

I jacked up the car and found no play in the tierods or ball joints.. Everything seems tight. The shaking was the same with my stock wheels as well. Occurs at the same speed, slightly diminishes at around 80-85mph but you can still feel the vibration. I don't think it's a balancing issue, I've had my current wheels balanced twice by two different shops.
I'm getting polyurethane rack bushings tomorrow, but what else can possibly be bad here? I doubt it's motor mounts since it does this with the engine off as well.

Could out of spec caster/camber cause this vibration? I'm sure it's way off since I installed my cc plates and have yet to get it aligned.

 

[Dsg-shaker]

Out of round tire? Or a under inflafted tire. That's first thought usually what I see with front end shaking between 45-55, but that's with a slightly bigger tire... Check and advise?


Sent from inside a shipping container.

 

[Black01Vert]

It has done the shaking with 3 sets of tires already, all inflated to 32psi. The shaking begins at 55mph and doesn't diminish till about 95, even then it still shakes a bit.

 

[tropicmustang]

I would have them road force balanced. if everything is tight suspension wise. I would start looking at different areas. Does it make a lot of noise like a bad bearing. i wish i could see the car. its just make sure the tires are not out of round first.

 

[tropicmustang]

I would check the motor mounts and such. a bad motor mount can cause a shake like that.

 

[Black01Vert]

I will get them road force balanced this weekend along with new polyurethane bushings on the rack. I'm taking the car to a different shop to get it aligned and hopefully all goes well.

 

[tropicmustang]

Yea man although an alignment thats out what cause a problem like that. hopefully you get it figured out.

 

[flamedstang95]

Ever figure this problem out?