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I have a 2002 Subaru Outback with a 5 speed manual and 160k miles on it. The previous owner claims to have replaced the front differential, because it was locked up.

Now, I have been hearing whining noises coming from around the transmission (hard to say exactly while driving) for a while now, and figured it was a bearing somewhere that I don't want to deal with right now.

But yesterday, it started making really awful clunking and grinding noises whenever I'm in gear, especially while accelerating. I do hear clunking and squeaking while turning tight corners sometimes, but not exclusively.

I'm not really familiar with Subaru drivetrains, or manual transmissions in general, but everything I'm seeing and hearing online is suggesting the center differential.

Does this sound like a center diff to you? How would I tell if it's the front or center diff? Do I even have both of those? Could it be a bearing in there, instead of a $500 differential unit?

I'm clutching at straws, because I really don't have time or money enough to throw parts at it and see what sticks.

UPDATE: When I checked the dipstick on the passenger side of the transmission, the only dipstick I can find, I didn't see any problems. However, on starting to drain the fluid from the tranny, it was pretty much made of glitter. Metallic flaky stuff permeates the oil. Bad sign, no?

The clunky sounds have gotten a bit less ever-present, especially when the transmission has warmed up a bit, but it is still pretty much always making a whining or light-grinding noise.

In my mind, it's starting to sound more like a transmission. Anyone else with more expertise on the matter have anything to say?

Thanks for your help diagnosing this, in advance.

  • Check all the fluid levels in the trans and differentials. – Moab Aug 13 '16 at 20:19
  • @Moab The manual trans has plenty fluid, and if I'm not mistaken the front diff is integrated there. It's definitely coming from the front of the car, so the rear diff isn't an object. However, you can't just check the fluid levels in the center diff; it's a sealed unit within the transfer case, so not only do I have to take the car apart to get to it, but I wouldn't be able to check the fluid level when I got there. – FireSBurnsmuP Aug 15 '16 at 20:31
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My WRX is a somewhat different setup but, Subaru being what they are, most of the equipment is very similar.

But yesterday, it started making really awful clunking and grinding noises whenever I'm in gear, especially while accelerating.

I suspect that this is where your "glitter" is coming from.

I do hear clunking and squeaking while turning tight corners sometimes, but not exclusively.

I suspect that this is a different problem (or set of them?). I'd be more worried about wheel bearings and front axles than the transmission. However, that's going on my personal maintenance history and your situation could be different.

Does this sound like a center diff to you? How would I tell if it's the front or center diff? Do I even have both of those? Could it be a bearing in there, instead of a $500 differential unit?

It could be the center differential but it's a little hard to tell even with the differential out of the car. If it isn't visibly broken or cooked, there's nothing to check since the unit is sealed.

UPDATE: When I checked the dipstick on the passenger side of the transmission, the only dipstick I can find, I didn't see any problems. However, on starting to drain the fluid from the tranny, it was pretty much made of glitter. Metallic flaky stuff permeates the oil. Bad sign, no?

Yes, this is troubling. It's possible that something in the transmission let go and has been getting progressively chewed. That situation isn't going to get better, though you might delay the real repair by changing the fluid frequently.

The clunky sounds have gotten a bit less ever-present, especially when the transmission has warmed up a bit, but it is still pretty much always making a whining or light-grinding noise.

For what it's worth, a bad center diff should be making more noise when warm in slow turns rather than less. That might indicate a lower chance of a bad center diff and point you towards the rest of the transmission. However, I wouldn't take that as evidence that it isn't the problem.

It's possible that both the center diff has failed and another non-critical part (e.g., a synchro) has spit some teeth into the rest of the transmission. I would say that there's a solid chance that you're looking at a full rebuild of the transmission.

  • That's pretty much the conclusion I ended up coming to - full rebuild. It didn't really feel like the center diff, more like a tooth missing (or two), and the mechanic agreed. I can't afford a 4K (USD) repair on a car only worth that, and I don't know jack about rebuilding transmissions, so I just swapped the transmission out of my 2000 Legacy and put a new clutch in it, and we're good to go now. Thanks for answering! – FireSBurnsmuP Sep 20 '16 at 13:24
  • @FireSBurnsmuP, glad to hear that you were able to keep rolling! – Bob Cross Sep 20 '16 at 13:30

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