Touché to anyone that expressed doubt that it was the rear differential. I dropped in the 3rd Member from ECGS over the weekend and can report that I believe the noise was 100% unchanged. I learned a lot though and am not as disappointed as I thought I would be in this scenario. I did grease the u-joints that I could get to so it wasn't a complete loss. I'll also note that while I doubt the fluid had been changed anytime recent, there weren't excessive shavings or anything.
I do have the following update regarding the swap itself. Anyone with any technical skill at all could typically do that swap. That said...what should have been a three hour job took closer to six. Between my father and myself, I bet we tried 20 times to seat the new 3rd into the housing (and failed each time). At some point we got fed-up and removed the sway bar. I was able to at that point successfully seat the 3rd in on the first try. I think that bar might actually be bent a little, which makes me wonder how it was bent in the first place. It was essentially blocking the 3rd just a small amount towards the top, and I kept trying to sorta "go under the bar with the top of the 3rd's upper flange lip and then seat it" but it kept binding every time.
Regarding the noise, I have three current working theories.
- Wheel Bearing (either left or right on rear, probably rear but may be front.)
- Wind Noise
- ECGS 3rd Makes the Same Noise
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So, if it ends up being a wheel bearing, I'm extremely disappointed in that shop I took it to. I stopped by there during lunch and explained the situation. He told me to come back later this week when the owner is there. So I'll be back. I don't expect this to go anywhere but we will see.
I'm wondering if it is a wind noise. A few months ago one of the roof rack covers must have fallen off somewhere because it is no longer there. I'm curious to see if this whole thing has been wind simply singing or causing vibration up top. I have plans to either borrow a cover from a buddy or try my hand at some duck-tape to smooth things out to see if the noise changes at all.
I have no experience with ECGS. It seems most people like them a lot. It it possible that the replacement just makes the same noise as the other one? On that note, I've started rather paying attention to other vehicles I drive and wonder if it isn't to some extent standard noise anyways? There is a Jeep at work with 50,000 miles on it and I'm not entirely sure it sounds much different.
I'm going to keep looking. The next place is to put it on jack-stands in the rear and see if we can determine anything. That honestly should have been one of the first things I did, obviously, but since I had a local shop diagnose it I really assumed they were correct.