New expensive sounding noise

Thanks for all the great ideas.

The car only makes the sound when I brake, and then the sound can remain for a few seconds after I let off the brakes; that's how I managed to get it on video. Normally, there is no sound until I hit the brakes hard. It was just dumb luck that I got it on video.

The sound happens if I use the foot brake or the e-brake.

No indication of scaring on the radiator or fan, so if the motor is moving forward due to bad mounts it isnt moving much.

Turning makes no difference.

I pulled the wheel and caliper off and there was nothing stuck that I could see. Caliper is torqued on per the manual.

Readjusted the e-brake shoes. No help. But I didn't adjust the cable, only the shoes. Not sure if that matters.

I replaced that outer CV joint a week or two ago. Maybe the clip at the end of the axle which keeps the CV joint on came loose and is floating around in there. That doesnt seem to explain why the noise only happens when braking. I really hope I didnt screw-up that dirty job.

It just occurred to me that around the same time I re-installed the guibo (the last shop did not align it correctly). Maybe those bolts came loose.
 
Peanut gallery speaks

I would not rule out drive shaft rubbing against an exhaust component. Check for wear marks.
 
Update

Earlier in the day I had the car on the road and I was still able to reproduce the new and expensive sounding noise (in third, hit the brakes hard and I heard it).

I brought the car home, put the rear up on jack stands and ran the car up to about 3k in third and hit the brakes trying to reproduce the sound. I tried it a few times, but no luck.

But I do notice a fair bit of slop in the differential. To me, this doesn't seem right and suggests the differential is the source of the new and expensive sounding noise. But I'm also wondering about that inner driver side CV joint which I did not replace. The earlier sound recording sure does sound like the source is nearer to the drivers side.

Click to play

 
Last edited:
In the drive-by video, I would have said something rubbing on the rotor - pad, shoe, backing plate, pebble. Pad not retracting?
In the new video under car, that sounds like something different to me. Clunk clunk, not squeal. Maybe excess play in diff but some play is normal. U-joints on driveshaft? Try holding each component in your hand while rocking driveshaft. What about axial play on diff front and side shafts?
What happens when you rotate wheels? Try rocking wheel in and out to check rear outer bearings.
 
if it did it while driving, but not when you had the car on blocks, it must tell you something about the loading of the car on the suspension ... perhaps something such as rear wheel bearings or the emergency brake because of the wheel bearings.

just a guess
 
Have you looked at your parking/emergency brakes? How about your brake fluid. Have you flushed recently, could you have binding going on due to old fluid and what happens to the systems?
 
Phemisg said:
In the drive-by video, I would have said something rubbing on the rotor - pad, shoe, backing plate, pebble. Pad not retracting?
In the new video under car, that sounds like something different to me. Clunk clunk, not squeal. Maybe excess play in diff but some play is normal. U-joints on driveshaft? Try holding each component in your hand while rocking driveshaft. What about axial play on diff front and side shafts?
What happens when you rotate wheels? Try rocking wheel in and out to check rear outer bearings.
Click to expand...

If you look closely in the video (I know its dark), Im turning the drive shaft several degrees in each direction. That motion is transferring to the U joint and into the diff. But while the drive shaft and U Joint is turning, the half axles arent. When I rotate the rear wheels, its the same problem. The wheel and half axle moves a few degrees but the drive shaft doesnt. How much play is OK in a 40 yo differential ?? Maybe this is a different problem.
 
rsporsche said:
if it did it while driving, but not when you had the car on blocks, it must tell you something about the loading of the car on the suspension ... perhaps something such as rear wheel bearings or the emergency brake because of the wheel bearings.

just a guess
Click to expand...

Maybe. I had thought that the load introduced under braking while the car was on jacks wasnt sufficient to replicate the problem--which I thought was in the diff when I saw all the play in the diff. But I must be over thinking this. "When you hear hooves, think horses not zebras". Back to the brakes for a closer look.
 
JhwShark said:
Have you looked at your parking/emergency brakes? How about your brake fluid. Have you flushed recently, could you have binding going on due to old fluid and what happens to the systems?
Click to expand...

I hadnt thought about the fluid being an issue. But here is a photo of the suspect wheel disk brake. The back of the disk has a mark, but I dont know what to make of it.





IMG_2496.jpgIMG_2497.jpgIMG_2498.jpg
 
Last edited:
I see nothing wrong with that rotor. Yes there's a band indicating some difference in wear or contact but it's not gonna cause a noise.

Dunno what to suggest but a clunk likes to come from contact between exhaust piping and the body. One backyard thing I'd try is to put a split bit of radiator hose or similar around the exhaust at the point of closest approach, then drive a bit. If no noise, then you've found it, hope this is all.
 
Play in the diff is common. Your UJ are a bit sloppy, but would not cause this noise unless they are dry under the boots. The boots look nice so i am guessing they were replaced recently so you might know if status of the grease inside.

No problems with the rear diff ever make squeaking noises. They are usually hard grinding noises, roaring bearing noises, or chunk noises.

My money is on this:
Rear wheels bearing or loose wheel shaft nut? With the car jacked up and the lug nuts tight is there any play in the wheel. Really try grab it and torque it around, front to back, top to bottom. If there is play it really messes up the alignment of the shoes inside and the pads outside. This would cause squeaking and come a go with braking. Also could change under acceleration and decel. Might even change the pedal pressure.... Pumping brakes gives better braking, but hard to tell with rear brakes.

I know of some other possible causes, but this fits all described

Good luck and let us know,
 
Just to close this out.

I took the car into Carl's this morning and he found it. The exhaust was lurching forward under braking causing the rear muffler to bang against the back of the differential case. My rear muffler is much larger than OEM so the clearance back there is tight, and maybe the motor mounts are getting tired.
 
You must log in or register to reply here.
Back
Top