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After surviving a week of the Flu I'm functional enough to surf a bit. I've read more center diff. stuff and now think it is more likely the rear diff.as it banged going straight. What bits could come adrift in there? I'd say there may be rust from boat lauch problems but anything thicker than a piece of roller race,circlip,or washer would lock up the rear and not work again wo increible noise. I know this is a dead horse but it may be a while b4 I'll get under the car. :blink:

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maybe a spider gear lost a tooth or 2 and sometimes 'skips' ???

 

good luck - let us know what you find.

 

If a spider gear let loose, it'd be catastrophic. If a ring or pinion gear "break" a tooth, it'll launch the chunk with enough force to blow a hole through the cover. 

 

A rear diff failure will NOT come and go. When they go, they go loudly with lots of collateral damage.

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I agree w that,but a realatively small bit like the axle circlip might come off(especially if rusty-80% winter use).  Squeeze noisily through the gears for a while then fall to the bottom to be picked up by the cold 90w later and repeat. Both times it didn't stop while moving but failed to reappear right away, Funny thing is that I believe the new axle didn't have one??  We're getting well and wife plans on working Friday so garage will be open for inspection. :rolleyes: PS further reading indicates the circlip stays in the diff. not on the axle so the new one shouldn't have had one on it. That reduces the ability of one to come adrift I guess. Tomorrow's to be above 32F so we'll get in then.

Edited by guzzijohn
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 Nothing in oil,magnet finds no debris either. I'll put some Valvoline syn/lube in there & cross my fingers. I've learned a lot from this problem and still hope for an answer. Any thoughts on viscous fluid in cold-both incidents happened right away on sub freezing days. :rolleyes:

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If a spider gear let loose, it'd be catastrophic. If a ring or pinion gear "break" a tooth, it'll launch the chunk with enough force to blow a hole through the cover.

 

A rear diff failure will NOT come and go. When they go, they go loudly with lots of collateral damage.

I have to disagree, I have seen similar failures in a newer style Toyota rear end where there was a sever grinding noise followed by a banging noise that would come and go. It made it extremely hard to figure out where the noise was coming from. In the end it was the rear end and the issue was resolved when it was replaced

 

I should also mention that the Toyota mentioned was an AWD with a simialer style rear end as a Subaru

Edited by mikaleda
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I have to disagree, I have seen similar failures in a newer style Toyota rear end where there was a sever grinding noise followed by a banging noise that would come and go. It made it extremely hard to figure out where the noise was coming from. In the end it was the rear end and the issue was resolved when it was replaced

 

I should also mention that the Toyota mentioned was an AWD with a simialer style rear end as a Subaru

 

If a spider lets loose, you can't drive at normal speeds like that. If you hear a grinding and banging, it's already shot and won't disappear for 15 miles w/o letting you know something is wrong. I've seen c-clip failures break a chunk of the ring gear off, and leave a silver dollar sized hole in the pumpkin from the force of it shearing. Car was able to be driven about 3 miles like that, but no faster than 5 mph. It made varying levels of noises in transit, but could not go 20 mph or faster. I seriously doubt that Toyota's rear if destroyed, all of a sudden got quiet and was road worthy.

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 Nothing in oil,magnet finds no debris either. I'll put some Valvoline syn/lube in there & cross my fingers. I've learned a lot from this problem and still hope for an answer. Any thoughts on viscous fluid in cold-both incidents happened right away on sub freezing days. :rolleyes:

 

 

If there was water in there, it's unlikely there would have been enough concentrated to form a large chunk of ice. If you raised the car to get at your pumpkin, and the sound comes back, please start looking at the struts, muffler, exhaust, rear crossmember etc. 

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If a spider lets loose, you can't drive at normal speeds like that. If you hear a grinding and banging, it's already shot and won't disappear for 15 miles w/o letting you know something is wrong. I've seen c-clip failures break a chunk of the ring gear off, and leave a silver dollar sized hole in the pumpkin from the force of it shearing. Car was able to be driven about 3 miles like that, but no faster than 5 mph. It made varying levels of noises in transit, but could not go 20 mph or faster. I seriously doubt that Toyota's rear if destroyed, all of a sudden got quiet and was road worthy.

This is true with a conventional style rwd car since %100 of the power is going to rear end, but in a Subaru on pavement is only transfering about %10 of the power to the rear end and that varries so its possible that rear end is not under power when the noise goes away. Don't tell me this can't happen because I witnessed it myself, I don't know exactly how the rear end failed and that's not the point. The point is the rear end did fail and it exihibited these exact sighns

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  • 3 weeks later...

This is true with a conventional style rwd car since %100 of the power is going to rear end, but in a Subaru on pavement is only transfering about %10 of the power to the rear end and that varries so its possible that rear end is not under power when the noise goes away. Don't tell me this can't happen because I witnessed it myself, I don't know exactly how the rear end failed and that's not the point. The point is the rear end did fail and it exihibited these exact sighns

Manual splits power 50/50. If the rear diff grenades It will feel like the clutch is slipping bad, and it'll be hard to get over about 25mph. It'll do that until the viscous coupler in the center diff heats up then it'll drive ok until you stop and the center diff cools off again.

 

On an auto trans car you can completely grenade the rear diff and it'll still drive fine because the autos power 100% to the front wheels All the time.

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  • 5 weeks later...

  Ok,nice cold (below zero)days bring it back but not as loud as in beginning. I think whoever mentioned brake fluid may have got it.  The rt/rr disc is not cleaning up like the others-rusty from lack of use end of sailing season to December. It still seems odd to have a once per revolution from a rust spot on a disc coming and going but if there's ice in the caliper who knows. I can't get it to vary when braking so maybe that corner is frozen. We're having a rather mild Winter so maybe I'll take that caliper apart next week.

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I'm a retired mechanic w a weird issue. I have a '99 Legacy 2.2 5 spd wagon w 170k. A while back I started hearing a mild hollow knock that matched wheel rotation frequency. Suddenly one day it got loud enough that I limped home under 30. I'd already checked the right side thinking it was disc or axle related. Upon checking the left axle I detected slight slop so I put in new one. That seemed to fix it-took a couple short rides and no banging. Today it was back! It soumds like a hammer attached ri a tire hitting w each revolution. I did have some water in the rear lube from a bit of partial drowning(I tow a sailboat)but not bad. If the diff. got rusty I'd think there'd be howling bearings and if it were really coming apart that would happen quickly.  The only other thing that comes to mind is the driveshaft which should give a noise frequency faster than wheel rotation. I'll get it up on jack stands tomorrow. I suppose it could be the right axle but I replaced that at 153k.  Thanks,Guzzi John-Stumped in Minnesota

Check struts where they connect to body. I had one that the rubber part separated on. It banged at different times depending on road surface.

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  ... The rt/rr disc is not cleaning up like the others ... odd to have a once per revolution from a rust spot on a disc ... I can't get it to vary when braking ...

 

If there is a Rust Spot on the Disc, but you can't get the noise to vary when Braking,

 

or the Caliper is malfunctioning, or that is Not the Culprit.

 

However, Please, let us Know the Results.

 

Kind Regards.

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Ok,nice cold day new caliper works fine but noise is back. Looks like I'll be takong the left rear apart Friday. It isn't consistant-went 2 mi. to library(noise),left there and quiet for a mile 'til left turn.  Went another 6 mi-noise all the way until 4 blocks from home then gone. Must be axle,bearing brake on left. Still does it once per revolution so don't believe bearing. We'll see tomorrow. Maybe I need Gremlin repellant! :wacko:

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  • 2 weeks later...

Ok,replaced right axle Tuesday. Below zero today,wife forgot cell so I brought it to her. No noise!!! So did both axles,stuck right caliper,changed diff lube. So strange-left ax looked bad w rust & cracked boots,right looked better-still had green paint & good boots. Can't wait to take axles apart. The noise when it started at Thanksgiving was so loud at slow speed I didn't think I'd make it 3 miles home. It is hard to believe it was just an axle joint.

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