Mechanic says I need a rebuilt diff. I'm skeptical. Thoughts?

I'd love a sanity check here. My 2006 E250 with the 4.6 and 325k miles has a slight wine or groan coming from the right rear tire during medium speed right hand turns. Been there for a while, maybe since I got the van over a year ago. 

I thought "wheel bearing" and had a (supposedly respectable indy) shop inspect it a few months ago. They said bearings were fine and couldn't duplicate the sound. I was skeptical (I hear the noise) but busy and took their word for it.

I finally got around to jacking the van up recently to check the bearings. I right away felt a very small amount of play in both rear wheels (right more than left) but with an audible clunking/metal sound from just inside the hub. The wobble was minimal, but the sound was more concerning to me. There was a smiliar, though less noticeable sound coming from the front with even less play. My hope was to fix the bearings before the axles are toast too.

So I take the van to another supposedly reputable indy shop (I am new to this area) and have them look it over this morning, telling them about the noise and the movement of all the wheels. They call me and say the bearings are fine, but that the differential is the problem. Say nothing of the front and quote me $3200 for parts ($2500) and labor for a Jasper reman'd unit. I say thanks but no. I ask if the diff could cause the wheel wobble, and the service advisor says it might be the pinion gears on the outsides of the diff. 

I'd love to hear your thoughts. I don't feel super trusting of this shop (and most mechanics) for a few reasons that I won't get into now but for one because the groan/whine is clearly coming from the right rear wheel and the clunking when I wiggle the wheel is seems to be coming from just inside the hub. I so often find that people don't check the things I ask them to check. I wish I had the tools, space, and time to just do everything myself with a trusted friend. 

Anyway, I'm thinking:

A. Get a third opinion

B. Do nothing and fix it when I get stranded.

C. Get a Eaton LSD and have someone install it for me down the road when/if I have more money. 

I'd love any insight into Ford van bearings, diffs, and WWGRM do.

I'd spend $300-$400 on a good used rear axle and u-bolts and swap out the whole assembly. 

Car-part.com list them with about 1/3 of your mileage for $250-$300 depending on whether they have 3.73 or 4.10 gears.

It could be a bearing. Could be high mileage. 

The clunk when you move the wheel is normal for a stick axle. IIRC those are c clip axles. They make noise as the shaft slides in and out of the housing.

At 325k it's going to make some noise. I'd run it until it's howling and go find a JY unit to install. 

I've run 3 of those to within shouting distance of 500k without issue. Run it and turn up the radio if the noise is bothering you. 

@No Time, thanks for the idea, that's another good option.

@Toyman, yes, I believe this axle (Dana w 4.10 gears) has the c clips. So it's normal to have that tiny bit of play (it's almost visually imperceptible) and the clunk (which was more what I noticed)? Good to know. Seems like a JY/car-part option with less miles makes sense. Looks like there is one in my area for $250, although unlisted miles.

Is this a full float axle or not? 

An E250 should be a semifloating axle.

If the axle seals are not leaking, I would not worry about it.  There will always be play and clunk, that is the nature of things.  The end float is controlled by the C clip/axle end/differential pin equation and the axle rides directly in the bearing rollers.  The axle is the wear item in that equation, and when things get worn, the first sign of a problem is the seal leaks because the axle sits too high in the rearend.

So if the axle seals are dry, and the fluid is full, should be good there.

That Said.  A whining when loading the right side could mean that the left side diff bearing is getting noisy.  Side loads are going to be loading that bearing through aforementioned axle/diff pin interface.  (Aren't C clip axles fun?  ) You should be getting noise when under acceleration in that case, but maybe not.  Either way, if it hasn't gotten any worse, it probably won't for a long time.

Yeah it's a semi-float. Dana with 4.10 gears.

Thanks Pete, very good to know. I was concerned that the bearings were bad and a) causing wondering on the freeway, which has been a long-standing issue with this van, and b) going to ruin the axle which I wanted to prevent by replacing the bearings. I'm just surprised that a sound that REALLY sounds like it's coming from the RR tire is the diff, but I appreciate that sound can be a funny thing.

No leaking so far, just the noise on right hand turns and the clunk I heard when I grabbed the wheels and pushed/pulled at 10 and 2, and 12 and 6. 

If and when I do replace with a JY rear axle, is it worth hunting down one with a Ford factory LSD? 

I've never driven an e250 or e350 that didn't wander on the freeway. Mine, uhaul, Ryder, they all wandered. 

When I'm not sure where the noise is coming from, I keep driving it until it becomes obvious.  Been down the road of throwing parts at something and the noise is still there.  The strategy of driving it until it breaks has served me well.  Done this with wheel bearings, u joints, pulleys for ancillaries.  Sooner or later it sorts itself out, but you really have to keep an eye on things so you do not end up stranded somewhere and have to pay for an expensive tow.  The van is 16 years old and has a ton of miles.  How much longer do you plan on owning it and how much money are you willing to throw at it to keep it running?

Toss 2k into that van and you can probably resell for 5k

I had rear axle noise and vibration I couldn't figure out on a 77 DeVille- finally put it on the lift, stuck it in drive and spun the rear wheels up to about 50mph and they were moving all over the place.  When I replaced the axle bearings the original ones pretty much fell apart.

All that to say, maybe put the back end in the air and observe what's going on when the wheels turn?

Yeah, I might try that if I can get a floor jack. I used the bottle jack to put one side up to check the bearings, but I am living in the van and don't have access to all of my tools. I doubt I'd see much if I did that though given when the noise occurs, but who knows.

@tr8todd, I plan on keeping this van for a very long time as it is built out for living in. 

Thanks for all of the helpful insight folks. Based on what I am hearing, I think I am going to do nothing until it gets worse and then replace with a used rear end assembly.