Driveshaft Carrier bearing failing?

[G.T]

i have this car that's showing a symptom i've not seen before on the S197 platform..
a constant repetitive knock from the rear end/driveshaft (certainly not the transmission/clutch/engine) and only on deceleration, and it's certainly not the vibration noise that you get with an out of alignment driveshaft, or a bad pinion angle setting... it's a distinctive clunking noise that comes from around the rear end of the car, and i can't seem to put my finger on it just yet.

i checked all the obvious, and checked the pinion angle with poly/poly LCAs and poly/poly adjustable UCA, the angle is at -2.5 at the moment (adjusting it anywhere from 0 to -4* didn't make a difference with the noise)

i'm starting to wonder if it's the driveshaft carrier bearing, or something else in the rear end.. it's kinda hard to tell as you don't get the noise with the car free wheeling (even with the suspension loaded up on a jack), i guess the driveline needs to flex like when it's on the road to induce the symptoms, which makes it really hard to pinpoint the exact source while looking under it :S

any ideas?

 

[scramblr]

You're certain it's not the normal driveline slop with the stock DS?

 

[G.T]

it's not that, the slop is usually noticeable as a single clunk when you load the rear end (accelerate), and another clunk when you lift of (if the slop is really that bad)
this is a constant clunk clunk clunk clunk that seems to sound with every rev of the driveshaft.. as long as the car is decelerating, till the speeds is below 10mph or so, not to mention there is no excessive slop/free play in the driveline from what i've seen

 

[KIMMER]

I didn't know you were still rocking the stock shaft on your car. Climb under the car and grab that center bearing housing and start jiggling it around to see if it has any slop.

 

[G.T]

Kimmer: it's a customer's car actually, then again mine is also rocking the stock shaft

to be honest i'm not a big fan of after market driveshafts as i've had quite a few of them dropped/dinged while shipping overseas, and i'm yet to find a decent place that can balance driveshafts here (the only one i've dealt with works on marine engines, and can only balance shafts within a limited RPM range)

anyway.. i'm done for the day, but i'll give it another go tomorrow, and i'll hopefully find something short of tearing the rear half of the driveline apart

 

[Nastystang06]

Ever figure this out?

 

[WILECYOT]

Shit, I have this same problem. Idk what it is but my cars only 6 months old now.

 

[86GT351]

Has the car recently been raced? I have experienced issues with them that the Pinion Bearing loses some preload over time and can cause a knock. Also if the Crush Washer was not installed 100% it can cause a knock. Other than that I vote for the Driveshaft issue also!

 

[G.T]

sorry for the lack of updates.. but i've determined the problem and it wasn't the driveshaft or differential..
turns out the axle shafts are bent!!

after spending countless hours checking all the obvious, i put the car on my scissor lift which has an auxiliary platform so i could have the suspension loaded while "driving" the car.. then i went around with a stethoscope and found the knocking was from the axle housing

on a closer look and with the wheels off, i could see the hub/rotor moving back and forth as the axle spun..

i got a set of moser axle shafts on the way, but i'm worried the axle housing maybe a bit out of shape.. let's see