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Testing CV Joints Posted by Arabiflora [Email]  (#1129) [Profile/Gallery]
(more from Arabiflora) on Thu, 4 Feb 2010 01:28:13
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I previously posted my theory that the intermittent shaking in the front end of my 88 900S (NA) might be attributable to wheel bearing failure(s). I was quickly and effectively disabused of that hypothesis by folks that I trust on this site, a condition made easier by the fact that all the shaking went away for the last 500 miles or so. But it's back, it's unnerving, and I need a diagnosis.
The gist of the problem is this: My Saab has occasional bouts of palsy. Ordinarily she runs true and firmly down the road, but has lately shown instances of instability in the front suspension-- the steering wheel begins to jerk rather aggressively as if one or more of the front tires were loose. It's not a rhythmic jerking but is about evenly distributed between sudden lurches to the left and right when it flairs up. It is most prone to occur upon drastic release of engine torque-- e.g., popping the clutch at 35-55 mph in anticipation of a stop light or taking my foot fully off of the pedal when nearing a sharp curve. Sometimes I can sense a weaker wobbling in advance of gran mal seizures, but when they set in firmly the car scares the hell out of me and I look for a place to park.
And here's the weird part-- I've found that I can almost always cure the seizure by parking in a slot from which I can conduct a tightly arcing turn in reverse, put it forward gear, and go on as if nothing ever happened-- sometimes for many miles. If it helps in forming a diagnosis, I will also note that I have experienced a marked under/over-steer condition as of late: cruising at, say, 45 mph, if I accelerate the car pulls right, if I back-off it wants to draw left; I've never noticed that effect prior to the greater symptoms of shaking.
Please tell me where to look for the likely culprit(s). The wheel-tug test (and the reasoning of others in response to a prior post) discount wheel bearings; ball joints have been recently (<10k miles) replaced, as have rotors and pads. I will admit to hearing some 'ca-lumping' on tight turns (particularly when in reverse) which I've dealt with by avoiding same. A-arms and shocks look fine, or at least not noticeably defective (the car has 392k miles and so nearly every part is now defective to some extent as compared to new).
My most recent hypothesis is that one or both CV joints have gone bad. The CV joint boots are intact but of course that means little as regards the integrity of the parts within. I've searched very hard, I think, to find on this site a way to test that hypothesis-- Are the CV joints bad?-- but have found no definitive instructions or other guidance.
Should my latest "diagnosis" (CV joints) be equally as error-prone as my first (wheel bearings), I will nonetheless welcome any helpful pointers that could help me address this nagging problem. At the least, anyone with a definitive answer to "How to check CV joints" should post same in reply. I'm surprised that the answer is so elusive given the wonderful traffic and advice on this site.
My thanks for bearing with the length of this post, any and all suggestions will be greatly appreciated.
--Scott
, Thu, 4 Feb 2010 01:28:13 <-- Viewing This Message
, Thu, 4 Feb 2010 07:25:46
, Thu, 4 Feb 2010 08:36:47
, Thu, 4 Feb 2010 04:59:05, Thu, 4 Feb 2010 08:01:57
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