So, I've been trying to solve this problem for some time now. Driving on normal surface roads, the car behaves as usual. When I get up to 60-65, the steering feels very light and requires constant correction. If you've ever driven an old car or truck with a steering box, you know what I'm talking about.

Now for what I've checked/done to try and fix this. Replaced all 4 springs/struts with low mileage S4 parts. Installed S4 rear sway bar (new end links are sitting next to me waiting to be installed). Got an alignment and changed tires.

I've checked tie rods, ball joints and bushings. None seem to have any play or noise.

Where do I go next? I have read that there is some sort of steering damper on the 2.8 cars, which I have. The car has 150k on it, so it very well could have failed. I assume that this is just like trucks and the like to keep the wheels from telling the driver where to go. Could this be my culprit? Can it be removed without removing the whole steering rack?

 

If it is the damper, you'd have to pull the rack to change it. Look in the DIY section - I wrote up a rack replacement procedure that you can reference. Another thing though, which is more likely (since as far as I can figure, the damper is simply a fluid tube like a shock absorber), is your inner front CV joints. When they go, you don't get the typical clicking like you do from the outer joints since the inners move very little by comparison. They do cause straight-line instability though, and speed exacerbates the issue. I'd inspect them any way you can to see if you can nail or eliminate them as the cause.

 

I had the inners off when I did my clutch about 5k miles ago. I wasn't inspecting them per say, but didn't notice anything abnormal. I've never heard of this problem. Is it just the fronts that cause trouble, or should I be looking at the rear as well?

If they are bad, can I just replace the joint rather than the whole shaft? ECS sells just the inner joint for nearly the same price as the whole assembly. Are the re-manufactured ones from the parts stores any good?

 

I had some time to crawl around under the car today after work. Sure enough, the passenger side inner CV has some play to it. Both shafts move along the longitudinal axis, but pushing up and down on the inner on the passenger side produces a click.

Now, do I get the joint alone from ECS, ect. or buy the entire re-man assembly from the local parts store?

 

I'd probably just replace the axle. Cost is similar and there's less work involved in axle replacement than axle rebuilding. The flip side is, replacing the joint means you keep your OEM axle shaft, which seems to be beefier than the aftermarket axles I've seen.

 

Thanks for the tip on the CV joints. I'll replace them both and let you know how it turns out. Since your returning the oem shafts as cores, I'd figure that they would reuse the shafts. We shall see.

 

Replaced both front shafts. Issue seems slightly better, but not a major improvement. I'm thinking of taking it back to the alignment shop. Any other thoughts?

Does anyone else have a suggestion?

 

There is a valve in the power steering pump that adjusts flow based in rpm. This would make steering very sensitive at highway speeds like it is off idle. Try changing the fluid and cleaning out the metal filter in the res. If that doesn't work, you are looking at a new pump.

 

I had considered the speed sensitive steering (I think Audi calls it Servotronic). I figured that if it had failed, the steering would be heavy all of the time, rather than light.

Is the actuator for this on the pump, or the rack? The A6 diagrams I've looked at show it on the rack rather than the pump. I haven't found a diagram for the A4. People mentioned pulling the relay on the A6 because they thought it made the steering too light. I've looked through the wire diagrams that I have and see no mention of a circuit to change the steering at speed.

Is the system in the A4 purely mechanical? If it were only based on RPM, it seems that the steering would get heavy at low speeds when pulling away from a stop in first revving to higher rpms than cruising on the highway at 2800rpm.

I had thought of just changing the fluid, but want to know more about this steering system before I buy fluid at $40/L.

 

Pentison is about $15 and it's full syn is $22. Picked mine up at o'riellys. Only really need a can