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smayo964 06-23-2012 03:26 PM

99 Z3 Ratchet Noise From Rear
I humbly summon the Z3 Powers and the knowledge bank. Just heard something weird today. Released the clutch today to leave a red light and heard a slight "ratcheting" noise coming from under the car in the driveshaft or rearend area. Sounded like mating splines jumping across each other. It was real quick and didn't happen again the rest of the day. I hammered on it later in the day thru the gears and nothing. Any thoughts on where to start looking? :dunno: Thanx in advance for once again tapping the brain trust. :D

smayo964 06-24-2012 07:30 PM

Just got back from a nice evening drive with the top down. Unfortunately, the ratcheting sound came back once leaving a stop sign for a second or so. I felt more, or sounded more like in the carrier bearing area. Granted, this is only happens in 1st gear. Anybody?

smayo964 07-03-2012 05:38 PM

Lets try this one more time. HELP!!! Just crawled under the car. Nothing appears to be cracked, broken, or misplaced. The wheels and driveshaft spin smooth and free. Half-shafts slide freely between differential and hubs. The only thing that I can think of is "did this start after I changed fluid in the rearend?". Frankly, I can't recall (cranial moment). I'm assuming I have the limit slip rearend due to that when spinning one side, the other was stationary and the drive shaft turned. Being that, could the fluid be causing the clutches to slip or "chatter"? Would the sound migrate up the driveshaft to the carrier bearing location and resonate thru the chassis? I put Royal Purple 75-140W in the rearend. Could it be causing to much slip? Any help would be greatly appreciated before I start excavating a car needlessly. Thanx.

ronpolley 07-03-2012 07:03 PM

I've had similar problembs on a vette, different lube caused chatter and popping.,did you look at the center bearing?

crappyattitude1 07-06-2012 04:56 AM

I also had a simular problem.....
In a Z-28... changed rear end fluid... forgot the special posi fluid and it "ratcheted" something terrible. Put in this "special fluid" and all was well.......

Of course that was a Chevy "Z"...... not a BMW "Z".....

Crappy : )

(Just outside of Nashville)

smayo964 09-13-2012 08:25 PM

I FOUND IT!!!!! I FOUND IT!!! :bigpimp::thumbup: The U-joint behind the carrier bearing was about locked on one side. The carrier bearing itself was ok, but to loose from the mileage. I replace the bearing and U-joint. It was like releasing the emergency brake and letting the car go free again. The drive train is definitely quieter and I can just about idle out the clutch and get the car rolling vs. having to bump the throttle previously.

For those who say you have replace the driveshaft, I removed the existing U-joint and replaced it with a NEAPCO 1-0431 (.947dia at the cap). $24.88 shipped. This is replacement for earlier BMWs and Saabs. The U-joint is about 1/4" longer over the caps and the ends lined up flush with the yoke and shaft castings. I used (2) 3/16" dia by 1/16" tall tack welds on each cap (180 deg apart) to keep them anchored it. Focused the weld bead mainly on the casting and not the cap. Just enough overlap to keep the groove obstructed. Must quench the weld zone immediately after welding to keep from any boiling of the needle bearing grease, etc. The joint also has a grease fitting so I lubed it up well.

I believe the hardest part of the job was getting the exhaust back in by myself. LOL Any, if the rear one goes out, I'll do it again. Just thought I'd offer what inexpensive fix worked for me.

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