Viscous coupler bearing whine AGAIN

[rgnjc]

So last spring I replaced the bearings in my viscous coupler because there was an audible whine that I wanted to take care of. The replacement went smooth, and it solved the problem. After removing the bearings, it was clear that one of the bearings was not smooth and was the cause of the whine. That was ~7 months and a few thousand miles ago, and everything was great. However, just recently I was driving down the road and suddenly I started detecting the same whine. Its too damn cold this time of year to mess with it myself so I took it to the mechanic. They said it was the a noise from the rear diff and that it would need to be replaced, though the oil looks good so no damage to the gears. So I'm looking at doing the fix myself again. Why replace the whole rear diff if its just the bearings, right?

Can anybody shed some light on this? I'll replace the bearings again myself when it warms up a bit. The oem bearings are cheap enough on toyotapartsdeal.com, and its a fairly easy job and doesn't take long. Am I overlooking something here? I'm perplexed why the bearings would fail again. Could they have been faulty and its just a coincidence? Perhaps my repair job was not up to par? Or is it possible that there is another issue (with the rear diff, or an out of alignment drive shaft) that is causing the bearings to be damaged. Though, there are no other apparent issues.

2005 Vibe AWD, 175k miles

[rgnjc]

PS: The transmission was replaced over a year ago, and I've had some trouble with various components of the drive train since that replacement that I've more or less solved. The transmission blew at 65mph and wreaked havoc on many drivetrain parts, and I believed this was the cause of the first bearing failure (a CV axle was damaged too and needed to be replaced). The car does however have a shutter/vibration when the car switches from 2nd to 3rd, and 3rd to 4th. However, this car has always had that since I got it at 38k, so I'm not sure its related (Could it be something with the rear diff?). Also just FYI, when I replaced the viscous coupler bearings, it was fairly easy and I followed the directions at: https://www.youtube.com/watch?v=GOd40uoc1SU

[zbyers]

Did you try just draining and refilling the diff to see if that solves the noise.

Is it possible it's a rear wheel bearing making the noise, and not the diff?

I find it unlikely the viscous coupler bearing died again in such short time/mileage.

[andrewclaus]

Ditto the above. And try an additive. I once had a Honda CRV with the viscous coupler in the rear diff. It developed a whine. The transmission guy recommended an additive and that solved it for its long remaining life.

[rgnjc]

Well the weather finally improved and I got around to looking into this further! Following up on my previous suspicions, I pulled the viscous coupler off today to inspect the bearings I replaced 11 months ago (~5k miles ago). The front bearing was smooth and buttery, and otherwise like a brand new bearing. The rear bearing however was gritty and making noise, its clear there is damage and the rear bearing will need to be replaced. I just ordered the rear bearing on toyotapartsdeal.com and it only cost $20. It'll be here in a few days and I'll report back on whether or not the whine is gone (I suspect this will solve it).

In the mean time, what might cause bearing damage? The fluid was basically brand new and topped off from my repair a year ago (fluid still looks great). Like I said previously, sometimes I get vibration when the car is about to go up a gear, but the car has done that since I got it at 38k miles and its never been a problem. Last year I believed the bearing got damaged when the transmission blew out (a number of drive train components needed replacing). However now I'm thinking there is something else causing the viscous coupler bearings to fail. Could my installation job perhaps led to premature failure of the part? Or could it just be a faulty part? When I replaced the center support bracket on the drive axle, did I perhaps not align it properly when I installed the new part? Could this be indicative of rear diff problems (the fluid always looks clear and never has shavings or much magnetic dust). I guess time will tell and I'll see if it fails yet again.

I will tear the bearing apart later this week to see what type of damage is in there. Last year when I replaced this bearing, there the outer race was marred. I'll post in the follow up what I found, after I do the repair.

Also just for reference for others: The front bearing in the viscous coupler is Part No.: 90363-95007. The rear bearing in the viscous coupler is Part No.: 90363-65004. The dust deflector is Part No.: 41252-33010. The seal between the viscous coupler and rear differential is Part No.: 90310-54001.

[rgnjc]

Also, what fluid do you all recommend for the rear differential? I've been using Mobile 1 Full Synthetic 75W-90. Is there perhaps something better? Any good recommendations on additives for the rear diff? Maybe since I'm close to 180k I should put some additives in there.

Edit: I took apart the faulty bearing and here is a picture of the outer race. I'm not terribly familiar with types of bearing damage, but this looks like spalling to me. I'm not sure what would cause this though.

[rgnjc]

Just following up on this. I replaced the one bearing that wasn't smooth. The whining noise from the rear differential is gone. Although I fixed it, I'm still perplexed why the bearing would have failed less than a year after replacing it. Oh well, if it happens again at least I've gotten good at doing this repair.

[SSizler]

Thank you very much for providing the part numbers.
It has been a challenge to find them elsewhere.
genvibe.com ROCKS!