steering guibo/coupling/knuckle? to fix bump steer

[Richard7666 0]

Are the above all names for the same thing?

What BMW apparently call a "swivel joint with universal joint" www.realoem.com/bmw/showparts.do?model=AZ72&mospid=47632&btnr=32_0942&hg=32&fg=30

I see a lot of threads describing my issue at high speeds: bumps cause steering wheel to jerk, unresponsive steering wheel 'dead spot' when centered (ie lots of play either side of centre), despite having control arms + ball joints replaced, tires replaced, two wheel alignments later..

Just wondering if this part (assuming it's the same thing, though looks like it is in fact sold as a set of two couplings?) is likely my next culprit before tie rods or something

[jeffbebe 1559]

I replaced mine when trying to solve similar issue. It tightened up the steering a wee bit but the 'bumps' you're experiencing will almost certainly be worn shock absorbers, so I'm afraid it's unlikely to be a $50 fix.

Edited April 2, 2015 by jeffbebe

[Richard7666 0]

So worn shocks can cause steering wheel jerk? Makes sense.

The ride is fairly bumpy too

[jeffbebe 1559]

Yep, I'd start by checking the shocks - plenty of places will do shock tests for free, though you can probably see and feel easily enough if they're poked. The steering flex disk is easy and cheap to replace so no harm in doing that too!

[Richard7666 0]

Well, it seems to hold a line fairly well (moreso after ball joints, bottom arms, tires, alignment) though does deviate when it hits a bump.

If the steering wheel in my hands has a few cm of play before I 'feel' the wheels turn (feels like something is being engaged), would this point to the coupling?

On the other hand the ride is pretty bumpy, and in fact I could feel/hear what I assume was the rear suspension "bottoming out" (not sure correct term) over bumpy road at 100kmph after I picked up back seat passengers.

Edited April 7, 2015 by Richard7666

[jeffbebe 1559]

As Ron says, likely to be a combination of things. A worn guibo could result in a bit of play at the steering wheel but the shudder over bumps points to worn shocks. You'll also want to check the steering box and power steering system if you have to turn the wheel a few cms before the wheels engage.

The guibo is cheap and easy to replace so I'd recommend doing it regardless but I don't think that alone will fix your issues. Get the shocks and steering box/power steering checked properly and go from there.