Whine on Deceleration

[Jarsky]

Hey everyone. So I recently bough a new daily, its a 96 legacy 2.5gt with a 4aet and 120k miles. Had some wiring issues that I was able to sort out, but I've encountered a new problem. When driving above 30 MPH if i let off the accelerator, there is a high pitched whine noise. As soon as i press on the pedal even a little bit it goes away, and it changes with speed. I'm trying to hold out hope that I don't need a new trans. but it seems like that might be in the future for the car. I did an ATF change not flush change, and plan on draining and filling the front diff fluid although when i checked the fluid it looked good. My next areas of concern are the center bearing which I have a replacement for. From what I've read there's a potential it could be the gear lash, but i was unable to find how to adjust that in the service manual I have so im basically at a dead end. Anyone have any ideas besides find a wrecked car with a trans? 

[1 Lucky Texan]

the more owners soobs go thru, the more likely some fluid has been confused, so, wait until the diff fluid gets changed. Walmart has a synth-blend GL-5 folks seem to feel is a good value. And you get to examine the drain lug magnet for for excessive particles or, *gulp*, pieces.

[idosubaru]

Usual culprits are front diff or front axle. 

If you mimic the same conditions that cause the noise but do it while 1. Going straight 2. Turning left and 3. Turning right 4. Uphill,  are there any differences?

A free test, or waste of time, would be to swap both front axles left to right. This reverses the loading and will change the noise if it’s axle related. But if they’re old and may need new grease or boots this might not be a total waste of time.

Is either axle a non OEM replacement? Those are highly problematic when new and with age. Or They can also just need grease - the grease gets old and will just pour out like liquid. Cleaning and regreasing can quiet them up  

Change diff fluid and look for any signs of metallic particles or chunks in it. 

Driveshaft ujoints or carrier bearing and potentials but I’d expect