Vibrating shake when you hit a bump

Once again to the fountain of knowledge.

My 87 S4 has begun a problem.

I think it was after I hit a huge pot hole in NJ on turnpike. However, problem did not manifest until a week later back in VA.

When driving you can feel a vibration (back and forth) very short throw and rapid when the car hits a bump. It does it more frequently when the car is just started up and as you drive for 25 mins or so, it will go away and only reappear so often.

It does not occur at speeds under 40 and a quick jerk of the wheel will settle it for a few seconds and then the "reverb" works its way back in.

When at 60 or so, I almost never feel the reverb. It is primarily between 40 and 60mph.

The shake can be felt in the whole car, but most violent on the steering wheel. Almost like a springing back and forth rapidly.

Thanks in advance for your thoughts and ideas.

My guess (and it is that) is that you have a slightly bent rim and/or a tire that has a damaged belt, perhaps with a bulge. They behave like a wheel imbalance and are speed dependent, and can interact with other slight imbalances that you might not otherwise have noticed. If it's a rim it won't change much over time, or at least not as quickly as tire damage that will tend to get worse fairly quickly.

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My thoughts too... Might not even be a visible problem. You can road force balance the wheels and check that...

www.ifitjams.com/steering.htm


Found this handy flow chart from your recommendation, said ALS could be cv joints. I will get tires tested today. Tks

So to be further clear on the issue. I was feeling a severe oscillation on the steering wheel along with the car shaking at 40=55mph. It was random and could be stopped shortly by turning the wheel sharply and then back to center. It only occured when going straight. Any bumb or road gap would set the rapid oscillation in motion.

I had the tires checked out for balance. Checked good.

Did the tire shake top bottom and side to side.

Movement noticed side to side. Checked the rack bushings and they are shot. Lots of play.

I have ordered a rebuild and will put it in next week. I will also do the tie rods and motor mounts while I have the rack removed.

Anything else I should consider?

If your referring to the external rack bushings then I'd recommend the Delrin or Aluminium bushings Roger sells.....you dont need to replace the rack.

How old are the tyres and shocks? When the wheels were balanced were the tyres removed to inspect both the rubber and wheels for issues?