Hi all,

Rusty is making it hard for me to like him. He seems to have an issue with some kind of imbalance at the front.

At all kinds of speeds, the XJ will run smooth for miles after miles. But then all of a sudden start to wobble. So hard that when you brake, you feel it then too. If you slow down again the wobble goes. Accelerate to the speed before and it will smoothen out again...

Now, I can't think much more than 4 possible candidates:

1. Badly balanced wheels but then it wouldn't come and go and smoothen out without slowing down or accelerating.
2. Bad shock absorber, as the ride is rather soft.
3. Worn bushes, as the steering is sloghtly vague.
4. Brake disc warpe, but then it doesn't always wobble and shake when braking hard or nornally.

What could be the problem? How likely are woran bushes/shock absorbers on the sluggomatic 3.2l V8?

Cheers people!

Damien

 

I would bet on worn shocks, bushing or upper mounts. Badly worn sway bar busings and links, as well. Maybe worn ball joints?

This assumes smooth on a smooth road, but any roughness sets up a harmonic vibration that gets progressively worse. . .

If this is true, you can rule out worn and out of balance tires, out of round wheels, and badly warped rotors.

 

+1 for what Jim said, and I know from experience that tie rod ends can do the same.

 

That's the thing... Even a smooth autobahn can cause the (my feeling) front (right) wheel to start to bounce. Even on smooth road. When you then brake the entire dash will vibrate. A couple of seconds later it doesn't anymore...!?

 

Swap right side tires

 

What is happening is that a resonance in the suspension is being excited by various things : braking, bumps in the road, and so on. Ever seen an old car driving along with the wheels violently bouncing up and down? You see it a lot here in California, where there is no regular inspection. In the UK they used to test the shocks at the MOT.

Shocks 101 : They operate at two frequencies : firstly, the resonance of the body on the springs, which is very low. That is what the bounce test can test for.

Then there is a second, much higher, frequency of the unsprung weight of the suspension components interacting with the spring. The shock needs to damp this resonance too. It's a demanding job, damping two very different frequencies.

The first check should be removing the shock, and testing it. It should not be easy to move quickly.

My guess is you have wear throughout the suspension, including the shock.

 

Done... Even had it on the winter tyres Even swapped left to right and right to left as I have nondirectional tyres.

No difference. That is why I can cross off the buckled wheel/badly balanced wheel.

 

I was hoping not having to do that, but luckily it isn't a hard job to do so...

I'll book this Saturday then to check the shocks. Luckily I don't have CATS.

 

Could it be drive train related? I have a lot of drive train vibration that under some load/cruse conditions makes lots of noise/shakes. Most of the time it feels like its from the front and center. Give your drive shaft joints a look.

I have a 100% rebuilt front suspension (EVERY bit of rubber, ball joins, bushings, bearings, and a few alignments. I do have failing drive shaft components, diff pinion bearings, and output bearings. Replacing my trans mount and 1 Guibo helped for a day, then back to bad noises and lots of vibrations...

 

Okay then...

Car was on the lift today and I checked all bushes and ball joints up front. None are worn. All are nice and tight. The rubber seals of the joints seem all fine too, one is a little brittle (lower right) but otherwise still nice and stiff.

So, I can only assume: the shock absorbers are worn... At least they will probably be... I haven't got a shock tester here anywhere but I'll see if I can find one. Brakes and wheels were checked again... Not even a fraction buckled or warpped...

Luckily, the shocks can be easily swapped without the car being on a ramp/lift