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2009 legacy se 5 speed manual  with 40,000 miles. Everything has been working perfectly, until this morning. Wife calls me this morning and says the rear wheels locked up on her way into town. The car skidded to a stop and died. After a few minutes she was able to move it off the road and we let it set for awhile. I drove the car the two miles back home with no issue. Later in the afternoon I went to pick up my daughter and the reading on the dash computer was reading no more than 9.5mpg and there is a grinding noise under the seat upon acceleration. It does not seem to have power loss. Being new to Subaru all together i have no idea where to even start. 

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sounds like something in the transmission tail section or behind possibly a bearing or differential? have you checked the rear diff fluid? carrier bearing for the drive shaft? sounds like something ceased

 

put the rear of the car on ramps or jack stands and have a good look from the transmission back after checking fluid levels and color/metal shavings.

 

check the rear diff oil level from under the car and use a flashlight to inspect every joint and moving piece.. if you find nothing its most likely viscous coupling or internal trans damage.

 

my money is on a rear diff problem I think thats the only thing that would cause only the rear wheels to lock up at once are you sure it was both?

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Could be something with the rear brakes binding or sticking or something with the e-brake. Can you smell any odors? An overheated brake pad will stink like a burned up clutch does. It'll also lower MPG while binding as the engine has to work harder to move the car. Might not be enough to notice a difference accelerating. I know I've had a right rear locking on my Saab in the past. I didn't even notice it (and I'm super alert to any changes) while driving until I came to a stop and could finally smell it. Be VERY careful and get it diagnosed ASAP as a rear brake lock up on a wet road = rear kicking out and a crash. Very dangerous, lucky your wife can drive and stop, most people flip out and actually end their life that way.

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Thank you guys. We drive about 30 miles a day on dirt roads. Tore apart the brakes and found that the calipers were clogged up with dust. Rebuilt the calipers and drained, refilled, and bled the brakes. Everything working fine now.

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Hubby spoke too soon. The car is now making a noise when driving, upon acceleration, best way to describe it is really loud tv static. Sounds like its coming from the front, but I can't pinpoint a side, so could be both. Happened a couple times this morning, and the longer I drove, the worse it got. On my way home, any time I accelerated it did it, so I babied it. As long as I was coasting or stopped, no noise, only when accelerating. I drove a total of about 35 miles this morning, mostly back roads and town driving. Any ideas?

Edited by ali_mck

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Might be a vacuum leak or something loose. If it has a turbo, it might have a loose pressure-side charge pipe. When under boost (typically while accelerating) the turbo is trying to pressurize the intake (it's essentially an air compressor). If there's a leak, the air coming out will sound like a bunch of noise, could sound like "TV static". Vacuum leaks, depending on where the leak is, can whistle, buzz, howl, etc. 

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Does it stop making noise when you start pressing the brake pedal but still accelerate? 

 

Was any work just done upfront? I'm wondering if the dust shield is touching the rotor. 

 

Might possibly be a heat shield on the exhaust. I was getting a weird "zing" sound on mine (older car though) and found out the heat shields on both exhaust manifolds were "loose" around the main pipe, and the vibration from the engine was causing them to vibrate against the exhaust pipe while accelerating giving a "zinging" sound through the pipe.

 

Just ideas of top of my head. Maybe take a video of the noise if you can't figure it out as it'll help narrow it down. Given it's age and mileage, gotta assume it's something simple (hopefully).

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I'll make a video of my own tomorrow, but in the meantime, I found this video on youtube which sounds about the same to me. Noise is only on acceleration, like in this. 

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Given the low mileage of yours, I'm betting it's something else. Hopefully your video will help. Also, careful where you take it. If you go in saying "I think my front diff is bad" and they are seedy mechanics, they might figure out it's a dragging brake but come to you and say "Yep, it's the differential, it'll run $2500 to replace".....

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Dounds like front diff to me. I could imagine it is noisy if the fluid is low or gone, and has been that way for many miles. When was thelast time the car has been to a grease monkey?

 

Hearing that the noise goes away or lessens when off load, and the higher pitch whine on decel sounds like no oil in the font diff.

 

Go under the hood, and there is a 2nd shorter dipstick on the left side of the trans, near the speedo sensor, opposite side of the traditional ATF dipstick. This uses 80w90 gl-5 gear oil. Capacity is 1.3 qts. What you will find if it is dry is a stinky tarry mess on the dipstick!

 

The wheels would have locked up if the diff overheated enough and seized. Getting bad enough, it could sheer teeth off the ring gear causing for some spectacular driving characteristics.

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Fluid level was only slightly low. We're going to drain it and check for metal shavings. Thanks for the advice, I'll let you know what we find out.

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A bad wheel bearing can make a rumbling sound as well. Does the steering feel vague. Does the backend of the car wag around? IF the bearing fails enough, the rotor disc will side load the pads and ride against the caliper bracket.

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I'd get a magnet wand (looks like a pen with a telescoping shaft and VERY strong magnet on it's tip) and run that through the fluid. If any bits are there, it'll find them.

 

Also, if you can get the diff cover off, with the tires up in the air and trans in neutral, slowly rotate a tire and inspect all the teeth on the ring gear and pinion gear for deep gouging or unusual wear (you can mark a tooth with a special white marking compound, spin assembly, and observe each tooth is making identical contact), (check spiders if present) check the end caps for breakage, etc. If a tooth broke or is damaged, installing new ring and pinion gears isn't easy as you have to shim them for correct engagement (it affects noise as well) and the pinion gear requires a ton of torque to crush it's sleeve (I'm assuming Subaru is like other cars). One of the few areas I'll farm out on personal cars since it requires proper experience to do correctly.

 

Out of curiosity, did you run with a low tire for extended period, or mismatch your front tires? Did you make a video yet?

Edited by Bushwick

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No low tires. Will get video done in morning. Just had my friend's hub drive it, he's a mechanic, said sounds like its definitely coming from front diff. When my hubs is home tomorrow, I'll pull it over the pit and pull diff cover to check it. CVs are tight, maybe a couple mm play if that. The only things we found wrong when we had it over the pit yesterday were a leaky oil pan gasket and the carrier bearing is going to have to be replaced eventually. Not so bad that I'm worried about it immediately, just a little bit of play. Thanks again for all the ideas and advice, I'll post the video tomorrow!

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Here's the video. Checked the front diff fluid again this morning, barely showing on the dipstick. Getting ready to drain what little is left and see what we find.

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I dunno, that sounds like a heat shield rattle to me (or something else) on my stereo. Almost sounds like a cap rattling on something where it's hollow side is amplifying the sound. It seems like it didn't make any noise until after you accelerated it a bit and it shifted, then accelerated again and maintained a higher speed (more vibration). Usually a differential failure (it'd be a mechanical failure after all) would be a constant noise at all speeds, varying audibly with speed. Yours didn't make any noise until almost 40 sec in after the left turn. Also, the exhaust I think routes more to the passenger side too (does on my older car, not sure about yours). I also have something like 5 different heat shields, all of which can rattle. It's free to inspect them to be positive. Even an 1/8" gap on a shield from where it touches the pipe can cause rattling. I had the shields up under the heads "rattling" and it sounded like flywheel teeth rubbing the starter making a "zinging" noise. Another thing I've noticed with the weird engine layout of the boxer, is it transmits noise differently than traditional inline engines or even "V" engines.

 

Maybe someone more knowledgeable with these will hear something different than me, but given your mileage and age, I'd thoroughly exhaust inspecting the simple stuff first.

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Any luck with diagnosing yet?

 

 

This is off topic, but the amount of dust on those roads can and will clog your AC condenser and radiator fins over time. If allowed to pack in and settle for too long, you'll get premature overheating and AC issues. I've even seen this happen on semi trucks that have a radiator the size of a car hood. Easy solution is to take a garden hose with the nozzle removed, and let fresh water flow w/o force through the fins being careful to avoid the tip touching the aluminum. Should have a steady flow of water, otherwise it indicates blockage. At first the water will be dark and dirty. Once fresh water is exiting the opposite side, move to next section. If you remove the radiator fans, you can hit both units as there is a gap between the 2 so it might not get everything out otherwise. Disconnect battery while working on/near fans as they can start w/o warning.

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Had to order the T70 bit for drain plug. Hubs got hub assembly off and is trying to get CV shaft out now. I'll keep an eye on radiator, dust. Its awful out here. I'll keep you posted as we get farther, between our schedules we are squeezing in whatever spare time we have on the car as often as possible.

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Wheel Bearings, I thought it sounded like that, if the boots were broken hard dust particles can mix with the grease and grind those bearings down really fast. Hub play is an indication of wheel bearing wear.

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@39k miles that dust must be nastier than it appeared in the video. Makes sense though as it started slightly after the left turn. It took 105k miles in another car for front wheel bearings to fail, and it'd make more noise while going around left bends and quiet on right as it was loading the bearing differently. 

 

Might be a good idea to rinse the hubs down often as preventative maintenance. Makes me shutter thinking what your air filter looks like after 10k miles  :o

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Were going to start with the hub, it obviously needs replaced anyways. Keep your fingers crossed that fixes it. Only thing that kept me from that conclusion was that it wasn't a constant noise and louder than any bad wheel bearing I've ever experienced. The dust is horrible out here. We live out on scoria roads, that stuff pulverizes to dust and you can't see behind you for a 1/4 mile because of the cloud. I'll be thankful when the snow hits. I'll let y'all know what happens with the hub. Thanks again!

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