JLeake

I've heard CV joints popping on front wheel drive cars as they corner (and my former POS Nissan 4x4 truck...but that's another story), so I am well aware of what that sounds like. I took a long drive yesterday, and noticed a very faint knocking sound coming from the rear of the car. This sound was not like the sound of shot CV joints. If I would let off of the gas it would stop. I was traveling around 60-80 mph. It would come and go. Later I noticed it while decelerating (I think...it's very faint). I estimated the frequency of the knock to be on the order of 10 Hz. With a 26" diameter tire going 60 mph your at 13 Hz. So, should I swap sides (my axles) to be on the safe side? The CV boots look good, with no evidence of leaking grease. The car has 90k on it (86 951). Anything else it could be? Or have I identified an early warning sign of CV failure? TIA!

Type_LT

My cv's died about 88k or so on my 86' 951.

Skip

Sounds like CV's to me - just because the boots are in tact, does not mean the joints are good still. I just pulled a CV off an abused track car and the CV Moly literally *ran* out. Most others are simply dry.

FWIW, a frequency of 10hz would not be audible to the human ear. The frequency of the sound you may hear is a repitition rate of the all 6 ***** as they pass a given point. This frequency, ball rate, would be multiplied by the shaft rate... 6SR = BR. If one or more of the ***** is more prone to noise than others, say #4, then you would (possibly in addition to) hear that harmonic of the shaft rate... 4SR... and the predominant harmonic thereof... 4SR, 8SR, 12SR(BR2), etc So, if the shaft were spinning at 1000RPM: SR=1000/60=16.6HZ, BR=SRxB=99.6HZ, 4SR=66.4HZ

Skip

JLeake

Guess I'll swap the shafts. Certainly wouldn't hurt to repack the joints anyway. I can hear an event occur at a rate of 10 cycles per second (Hertz), however the actual sound I am hearing (the clunk or knock) itself is obviously of a higher frequency. I was simply trying relay the frequency at which I noticed the sound...I didn't have a mic and a scope! (Knock on your desk twice in one second...hear that, eh?) Thanks for the advice...do you think there's any harm in driving on it for a few more days before swapping the shafts? And I just use plain moly axle grease, right?

Skip

The response about the HZ was more for fun than anything... I understand your concept, and it is sound ( )

Shouldn't do too much harm to drive on it that way for a while - some folks don't change them until they break!

I recommend Swepco 101 Moly Grease - but, some may say that's not fair to do so - so, YGMV (grease)... bwahahahah, oh, sheesh, I kill me... <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" />