I'm investigating a clicking sound that is heard when applying the brakes. The sound is coming from the right rear side of the car. I pulled the wheels off checked all the brake parts...all appears good, no apparent issues. While I was under there, I noticed what looks like an aluminum capped valve. The cap is loose, but does not screw on. There is a slight bit of oil leaking from the valve onto the axle shaft. It appears to be a filler valve for the axle. It pops down but does not snap into place...should it? I had some work done on the rear axle about 6 months ago (drain and refill) and it looks like this has evidence of some wrenching or vice grips on it. What is it?

This link has a pic of the part involved....TIA

 

I think it's just a vent. My guess is that allows excess diff fluid to vent out if/when hot, but the cap helps keep water/dirt from getting in.
Anyone know for sure?

 

I'll have to crawl under my vert this weekend to check it out. Offhand I would say that it is an axle breather, on the 4x4s we usually have a rubber tube that runs up to a higher point on the frame or body to keep water from entering when the axles are immersed.

Your original question about clicking when braking could be your wear indicators on your rear brakes. I know you said you checked them but how many miles on your current pads and did you check both outer and inner pads?

Weird but for every 4 wheel disc brake car I've owned the rears would wear out a lot sooner than the fronts. It was just the opposite for vehicles with just front discs.

BB
Semper Fi

 

I was composing a reply when John posted.

I'm curious, did they do any other work on your pumpkin besides R&R the fluids.

BB
Semper Fi

 

About 49k on the original pads. They looked okay but I didn't inspect them closely as I was more concerned with wear on the front pads...I should probably pull the rear wheels and check again. How does the wear indicator work?

About the diff work: This was the third time to the dealer to check a rattle sound from the rear end. I would describe the sound like "marbles in the diff", usually most notable at slow speed and turning the car to the left. The first two times (at 3k and 28k) they replaced the clutch packs per the TSB. The most recent time was about 3 months ago. The dealer claims all was fine and they simply drained and refilled the diff with oil and LSD additive. The annoying rattle went away but I'm beginning to faintly hear it again.