I just bought this XK8 and I have a problem with a vibration in the front end (I think). The vibration is at 40-50 mph and 70-75 mph. The car really seems to jump around. I have replaced all four struts, all four tires, had a four wheel aligment and replaced the front brakes (it needed them). Vibration is still there. Any suggestions on where to go next?

Herb

 

Possibly steering rack?

It's hard to advise without seeing the car. It must be something in the steering/suspension.

Best thing to do is jack it up and get a friend to move the wheels etc about and look for play in joints etc.

Edit: Is it happening when turning, accelerating, braking, bumps?

 

XKs are VERY sensitive to (even slightly) out of round Wheels.

A Tire Shop with a Road Force Wheel Balancer can check the Wheel geometry. There are companies that can straighten and re-finish bad wheels for about $150 ea.

 

Yeah... I was thinking bent rim, but it sure seems like the tire shop would have pointed that out when they were balancing your new tires. Like Paul said, take it to a place with a Road Force balancer, and ask them to look at your rims as the wheel is spinning to see if it is bent.

 

One would think Sam...I had 4 new tires installed this summer and I KNEW beforehand that I had one bent rim, but the "kid" who installed the new tires and balanced them said nothing about a bad rim. I had vibrations when done. (one might wonder why I had new tires installed when I had a known bad rim - because it was a buy 2 get 2 free deal and I couldn't wait until the new rim arrived). Anyhow, I brought it back to the shop when I received the new rim, they installed it free of charge, and rebalanced all tires again for me. I still had a vibration as described by Hlopato, so I brought the car to a shop with a Roadforce machine and it now is perfect!

 

Road Force Wheel Balancing can accomplish two things that may help...first, it checks the balance of the wheel / tire combination while under load, which sometimes finds imbalance where a traditional balancing machine does not.

Second, it allows for match balancing, which helped get rid of a vibration I had at 70 mph. All tires and wheels have slight "high spots" and "low spots," both in roundness and in weight distribution around the circle. Match balancing finds the "low" spot of the wheel and the "high" point of the tire, so these two points can be aligned to cancel each other out (somewhat).

Ever notice that little dot of paint near the rim of a new tire? That's the "high" spot, as detected by a machine at the tire factory.

The right tire shop with the right equipment, as suggested by our friends above, can probably make your problem go away.

 

I had a very similar sounding problem and went through all the same repairs. It was the rear prop shaft flange. The piece that couples the shaft to the differential. Ni idea how it went bad, possibly from being mis handled during a tranny rebuild a month earlier.

 

hlopato, They replaced the rotors when they did the brakes correct? Jack

 

I have two XK8 2000 conv. Both now are showing messages (restr. perf) one of them I have replaced the throttle body 5000 miles ago and it only has 65,000 on it.
I know the mic. I used got it off a used. Is it possible to rebiuld it myself with new sensers or do I have to get the whole TB?

 

You really should read the OBDII codes before assuming it is the throttle body.

If the problem is the throttle body, AFAIK, no source for the sensors has been identifed for retail, but there area number of firms that do rebuilds (search the forum) at reasonable rates. I believe there are critical adjustments when the sensors are replaced and the procedures are not publicly available.

Also, no disrespect intended, but it is normal practice on this forum to start a new thread if you are completely changing the subject (your post has nothing to do with wheel vibration).

 

I am so glad I found this forum, I too have vibration at 45 and 70 mph. Kept taking the new tires back to Tire Barn complaining about this, they would rebalance but nothing seemed to work, I was blaming the tires being crappy. Anyway I will find a place that has the RoadForce machine to see if maybe that will work, no one ever said I had a bad wheel.

Thanks for posting so much helpful information, everyone!