I have been experiencing heavy steering feel for some time now, suspecting the universal joint in the steering shaft, but since there could be couple of other causes too, I haven't felt like dropping 200 euros for a new u-joint just to test it out. I now sprayed some WD-40 to the u-joint and the steering feels properly light again! Let's see for how long, maybe I should try some lithium grease spray next, but I was unable to get the nozzle reach the u-joint. At least now I know the universal joint was the culprit of the heavy steering.

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09/2003 X5 3.0i
02/2003 X5 4.6is (non-runner)