Another "What's this noise?" Thread...

[the_bard]

Got a "new to me" noise on my '06 Baja Sport. I've done a bit of searching around on the forums, and the symptoms don't seem to match up well to anyone else's case.

 

Symptoms:

• Starts about 35 MPH, continues to get louder until about 40 MPH, then decreases until it disappears around 45 MPH.
  
• Disappears when I lift off the gas. Accelerating or maintaining speed results in noise.
  
• Mid to high pitch.
  
• Sitting in the driver seat, it seams to be coming from behind and to the right.
  
• Sitting in the front passenger seat, the wife says it's coming from behind and to the left.
  
• When she's sitting behind the driver seat, she says it's coming from underneath her feet.
  
• No vibration is felt at all... just noise.
  
• Volume is loud enough to be heard distinctly over the engine and road noise at 40 MPH. Rolling the windows down doesn't increase it.
  

 

Any thoughts before I get underneath the "caruck" and start wigglin' the driveshaft? I figure I ought to start there, and then consider the rear diff. I'll check the wheel bearings, too... though the sound doesn't appear to be coming from either side, I still ought to check them.

[porcupine73]

Hm I'm guessing this is an auto trans, almost sounds like the final drive reduction gear teeth.

[the_bard]

Heh. Concentrated on the noise so much, forgot to mention it's a manual tranny.

 

Oh, and I'm convinced one of the prior owners abused her on the back trails a bit. Looks like she's got a two inch lift, and she's sporting Mudrat front and rear bumpers. There are bumps and bruises on the body that are consistent with light offroading. More wear and tear on the mechanical bits than I account for, considering her nearly 60,000 miles. So I don't want to discount anything out of hand...

[the_bard]

Bump, plus more information. I took my cellphone and tried to get a good recording of it. It turned out well enough, especially after I amplified the sound in Audacity by 10 db.

 

 

The first ten seconds is just road noise, then the whine kicks in as I accelerated to about 32 mph. It's on and off as I get off the gas, cruising in traffic. At about forty five seconds, it's pretty evident when I get off the gas, and returns loudly when I get back on it a few seconds later.

 

Directionally... the noise migrates. I swear it's coming from the right rear at lower speeds, then migrates over to the left rear and left front at higher speeds. My wife will say it migrates, too, but depending on where she's sitting, the direction of the sound will be different from my experience.

[forester2002s]

How's the oil level in the rear-diff?

[Fairtax4me]

Supposn it's possibly the airbox on the throttle body isn't assembled correctly?

Only other thing to make sounds like that would be a driveshaft carrier bearing or differential.

Differential noise should be pretty evident at higher speeds (about 60) as well.

[88wacaroo]

Supposn it's possibly the airbox on the throttle body isn't assembled correctly?

Only other thing to make sounds like that would be a driveshaft carrier bearing or differential.

Differential noise should be pretty evident at higher speeds (about 60) as well.

Well I"m pretty good at finding weird/bad noises! But it"s kinda hard without actually being IN the car soooo My guess goes with a diff. noise like a pinion bearing is going bad... but like I said w/out something to touch to feel it"s hard... It could be a carrier bearing too...but it sounds like it"s going through the car... If you have acces to a lift I"d put it up in the air and drive it-where it does the noise the worst using the brakes-ebrake to put it under a load! If no lift put it up on jack stands-4. Good Luck

[the_bard]

Been a couple busy days at work, so I haven't had much time to check out any of the recommendations yet.

 

Didn't think about the fluid level in the diff; the noise doesn't change when turning, so I disregarded it. I'll need to reconsider that attitude.

 

I did get half an hour on Monday to get the left rear wheel up in the air. The wheel bearing seemed tight, no extra play. No sound other than the usual brake pads dragging slightly on the rotor sound. I ought to try it again, borrowing the wife's stethoscope.

 

The driveshaft's universal joint was tight, no play when I twisted each end in opposite directions. I couldn't listen to the center bearing and turn the driveshaft by hand, too; there was a relative lot of up and down, side to side play in that large rubber portion of the bearing, though. Airbox looked assembled correctly, but I might just take it apart and slap it back together. The intake is missing the little snorkus, but I had it sealed via plastic & tape before the problem occurred. Resealing it didn't affect the noise.

 

I'll get underneath 'er this upcoming weekend, and poke and prod more. I'm not brave enough to put the Baja up on four jack stands and run it up to 40 MPH... that just sounds like I'm asking for one of the stands to fail. That, and my driveway sits at an incline, with nary a flat spot on the property. I might be able to talk the wife into turning a wheel I listen with a 'scope. If we leave one rear wheel on the ground, the transmission out of gear, and turn one wheel in the air, that should turn the driveshaft, correct?

 

Thanks for the suggestions so far!

[Fairtax4me]

Unless you have dead level flat concrete I wouldn't recommend having the whole car up with the wheels spinning. Remove the wheels and use two lug nuts with washers to hold each of the rotors tight on the hubs. This takes inertia from the tires and wheels out of the equation. And if something slips, the car won't launch when it lands on the ground.

 

The term "differential" gets kind of loosely tossed around and used to describe the whole assembly including the ring and pinion gears. The ring gear, though attached, is not part of the differential. The ring and pinion gears are merely the final reduction gear set before power is sent to the wheels. The four small spider gears inside the differential carrier are what make up the differential (they allow a difference in speed between the wheels when turning). Those gears typically do not make noise unless the vehicle is turning.

The ring and pinion gears are what make the whine sound that changes pitch with throttle, and are far more susceptible to wear due to a low fluid level. Most of the heat generated in the assembly is from friction between the ring and pinion gears.

[the_bard]

That would explain the change in the noise following the throttle; let off the throttle, and it takes the load off the ring & pinion gears. Sounds like low diff fluid is the best theory so far; all I need now is time to get underneath it and take a look.

 

Worst case scenario: the gears are worn excessively. I don't have a reference handy currently, but I'm guessing the ring & pinion gears are internal to the rear differential housing. At that point, I'll be looking for a replacement differential (finding a matching drive ratio and LSD would probably be easier than finding one directly from a Baja).

 

Best case scenario: the fluid's low. I'm coming up on the 60k maintenance, so I ought to simply change the fluid anyhow. I'll check the fluid for metal, keeping in mind that lack of metal doesn't necessarily imply that the gears aren't excessively worn. Picking up a replacement differential at my leisure as a backup would be a good idea; I'll do some research to match up the final drive ratio and LSD from a donor.

[the_bard]

Swapped out the rear diff fluid this morning; what came out looked nasty compared to the new gear oil I put it. It was grey, interspersed with silver specks. Not sure if that's metal, or if the prior owner had used GL-S or put a limited slip additive in.

 

Since the owner's manual recommended GL-5 75W-90 (off the top of my head), I refilled it with Advance Auto Part's house brand of synthetic, making sure it was GL-5 cert'd 75W-90.

 

It didn't change the symptoms, though. It may have gotten a little quieter, but that could just be my wishful thinking.

 

Edit:

 

If I pull the rear diff out, is there a cover that I can pull off to take a look at the ring & pinion gears? Or does the diff housing have to be split? I'd imagine the latter would be a hassle. For that matter, even if I'm looking right at the the gears, is it likely that I'd be able to visually identify the source of the noise? If there's an obvious high spot or ridge of metal worn, that's one thing; if its a smooth surface worn into the gear teeth, I can see where I might not pick that up.

Edited November 29, 2012 by the_bard
Added the edit section.

[1 Lucky Texan]

what did the magnet on the drain plug look like?

[the_bard]

It had a thin layer of sludge on it; the color of the sludge was the same as the fluid, grey or dark grey. When I wiped it off on a white rag, it looks black. It had those same tiny shiny specks that were interspersed throughout the rest of the fluid. Consistence was about that of the heavy silicon grease we used to grease farm equipment with. There wasn't much of it, but enough to wipe away.

 

No really big jagged chunks of metal, unfortunately . That'd be too easy.

Edited November 29, 2012 by the_bard
Corrected the color description.

[Fairtax4me]

You probably won't see any big rough spots worn into the ring gear, but there are markings that will indicate excessive wear.

Lots of glitter probably means there is a fair amount of wear. This could be due to improper fluid but I'd guess water contamination to be a good possibility if the vehicle was used offroad. Heavy offroad use also contributes to excess heat on the ring and pinion gears and can cause the oil to deteriorate. This means it needs to be changed more often to prevent wear.

Plan on getting a new rear diff soon.

[the_bard]

Yeah, I was figuring as much. I figured the Baja had been (ab)used offroad before I bought it, but the price was too good to pass up. One way or the other, I'd be paying for it.

 

As for resolving it: should I look into a replacement diff, or is it worth pulling the existing and getting quotes on rebuilding it? My gut says to look up which diff it is (final drive ratio, etc.) and look for a donor from another model. I don't want to lose that limited slip, either.

[1 Lucky Texan]

Yeah, I was figuring as much. I figured the Baja had been (ab)used offroad before I bought it, but the price was too good to pass up. One way or the other, I'd be paying for it.

 

As for resolving it: should I look into a replacement diff, or is it worth pulling the existing and getting quotes on rebuilding it? My gut says to look up which diff it is (final drive ratio, etc.) and look for a donor from another model. I don't want to lose that limited slip, either.

 

I think I got only about 1/4 to 1/2 teaspoon fo sludge off my diff plugs so, maybe things aren't too bad yet?

 

used diff is probably best.

 

From what I've read, the viscous LS function might be worn-out by 60K miles anyway so, that may not be a factor. Outbacks with the All Weather package got the VLSD, if the ratio is the same, it opens up more cars to look for.

[Fairtax4me]

You can get a whole used diff for the price of a new ring and pinion set and all you have to do is put it in the car. Ring and pinion replacement is a lot of work and a lot of measuring and checking to make sure you get the depth and backlash right. If its off by even just a tiny bit you'll be replacing them again in no time.

[88wacaroo]

You can get a whole used diff for the price of a new ring and pinion set and all you have to do is put it in the car. Ring and pinion replacement is a lot of work and a lot of measuring and checking to make sure you get the depth and backlash right. If its off by even just a tiny bit you'll be replacing them again in no time.

It"s a shame you can"t jack it up and run it--that would be the cheap and easy way to find it....You can spend alot of time and $$$ and still not fix it... Good luck.

[Fairtax4me]

This is where it's nice to have a "Chassis Ear" kit. It's a set with a couple transmitters that you can stick on various parts under the car and a receiver that you take in the car so you can drive and listen to the noises that the transmitters pick up. You can track anything down in a matter of minutes. Very useful for diagnosing noises but not economically practical for an occasional DIYer.

 

How dark was the fluid that came out? Did you drain it into a clean catch pan and save it? If you put about 1/2" in a small cup (solo cup) is it still transparent or is it completely opaque?

I noticed you said the sound clip was amplified, but was the whole clip amplified or did you pick out just that frequency range? Some noise from the R&P is considered normal, and the fluid (if not completely dark with metal flakes) could have just been overdue for a change.

If the R&P are worn excessively the new fluid will probably look nearly the same as what just came out of it in a few thousand miles.

[the_bard]

This is where it's nice to have a "Chassis Ear" kit.

I ought to get one of those. I can see where they'd be expensive, though, especially with the "wireless monitoring" portion of it. Makes me wonder why someone hasn't taken a small audio recorder and rigged it up to a 'scope. Use a magnet to stick it to the body and the part you want to listen to, drive, then pull it and listen.'

 

How dark was the fluid that came out? Did you drain it into a clean catch pan and save it? If you put about 1/2" in a small cup (solo cup) is it still transparent or is it completely opaque?

It was grey, opaque unless I was looking at a very thin puddle of it. Even then, the "sparkles" were distributed throughout. It looked like somebody dumped a bunch of really small glitter into NeverSeize.

 

Unfortunately, I didn't have the foresight to save the fluid in a clean container; I assume that having it analyzed would the purpose, and it'd be worth the cost of the analyzing. Nope, I drained it into the pan I usually use for motor oil. There's always a little of the oil left over after I swap it into a recycling container, so the gear oil is contaminated. Whether it'd make a difference or not in the analyzing, I don't know, considering that I'd be concerned with the amount of metal content in the sample.

 

I did save the oil in the pan (haven't dug out an old oil container yet to transfer it into), so I just ran out to the garage and took a second look, scooping out the mixture into a clear plastic cup. I can make out the old motor oil (there's not much) and the rest of it is grey. Anything more than a 1/8" thick in the cup is opaque.

 

I noticed you said the sound clip was amplified, but was the whole clip amplified or did you pick out just that frequency range? Some noise from the R&P is considered normal, and the fluid (if not completely dark with metal flakes) could have just been overdue for a change.

If the R&P are worn excessively the new fluid will probably look nearly the same as what just came out of it in a few thousand miles.

 

I amplified the whole clip, without picking out any frequencies. The only reason I did that: the original clip required that I turn up the speakers and the computer's volumes to high to hear it. It's definitely not normal gearing sounds. At the ends of the speed range (about 30-32 MPH on the low side; 42-45 MPH on the high), it's pretty hard to hear and the engine noise covers it pretty well. At 35-37 MPH, normal speed for cruising around town, it's definite and loud. The engine noise doesn't come close to covering it up. I suppose I could with the radio; I'd have to be *cranking* it to do so.

 

I've seen dark gear oil before; I haven't seen it with this amount of "glitter". I don't remember using anything with the limited slip additive in it, though, so I'm left not knowing if the glitter is metal or LSA. If I had had half a brain, I would've drained it into a clean container for analyzing.

 

I'm okay with simply replacing the differential. Again, worst case scenario, I replace the differential, it makes no change in the symptoms, and I go chasing down another problem. I've gained experience swapping the diff, and I've got a spare laying around the garage in case it does die some day down the road. I've spent more on less educational endeavours :-p.

 

I believe the NA manual Bajas had a final drive ratio of 4.11 (feel free to correct me if I'm wrong; I pulled it off of NASIOC's forums and didn't remove the diff cover to count teeth). I also believe that the '00-'04 manual transmission Outbacks had a FD of 4.11, too. Seein' as the Baja's allegedly built on the Outback platform, it makes sense to me. So I've just got to hunt down a 00'-'04 OBW, preferably with a little amount of underbody rust and low mileage; maybe something that was totalled due to front end damage or the like.

 

If I want VLSD, I'd better be looking at an OBW that either had it as an option (good luck finding that info in a parts yard), or one that had the whole cold weather package (heated seats, mirrors, block heater). I'll also keep in mind what 1 Lucky Texan mentioned about the viscous fluid in the VLSD not performing up to task at high mileages. There's the clutch LSDs out there, too, but I haven't done much research in that area yet.

 

Any thoughts?

[Fairtax4me]

There are wired ear kits where you basically wear headphones and use a switch to pick which sensor you want to listen to. The wireless kits are just easier to use( no wires to get hung up). And cooler. :-p

 

 

Oil analysis won't tell you much more than what you can see with your eyes in this case. For engine oils there are many more sources of contamination and bearing particulate can be so small you can't see it, but analysis can detect it, along with water content, fuel dilution, etc.

Very dark fluid with lots of silvery particles pretty much means there is severe wear of some component in the diff. As far as I know Subaru stopped using clutch type LSDs in the late 80s early 90s, so we should be able to rule out clutch material as a source of contamination in the fluid.

 

Limited slip additives are either clear or amber colored from what I've seen and will not have an effect on VLSD units because the VLSD is sealed and uses its own silicone based fluid. It does not share the gear oil used by the outer parts of the diff.

 

I would expect there to be more noise from the ring and pinion at higher vehicle speeds as well but the road noise may be enough to cover it.

But with that much metal in the fluid I think we can safely say there is so e definite wear going on.

I'd try changing the fluid again in a few hundred miles or at least remove the fill plug and check the fluid condition with your finger. New fluid may help limp it along for some time, but eventually it'll give up the ghost. Problem with the manual transmission cars is when either diff fails (front rear or center) you basically get no drive in either direction.

[88wacaroo]

There are wired ear kits where you basically wear headphones and use a switch to pick which sensor you want to listen to. The wireless kits are just easier to use( no wires to get hung up). And cooler. :-p

 

 

Oil analysis won't tell you much more than what you can see with your eyes in this case. For engine oils there are many more sources of contamination and bearing particulate can be so small you can't see it, but analysis can detect it, along with water content, fuel dilution, etc.

Very dark fluid with lots of silvery particles pretty much means there is severe wear of some component in the diff. As far as I know Subaru stopped using clutch type LSDs in the late 80s early 90s, so we should be able to rule out clutch material as a source of contamination in the fluid.

 

Limited slip additives are either clear or amber colored from what I've seen and will not have an effect on VLSD units because the VLSD is sealed and uses its own silicone based fluid. It does not share the gear oil used by the outer parts of the diff.

 

I would expect there to be more noise from the ring and pinion at higher vehicle speeds as well but the road noise may be enough to cover it.

But with that much metal in the fluid I think we can safely say there is so e definite wear going on.

I'd try changing the fluid again in a few hundred miles or at least remove the fill plug and check the fluid condition with your finger. New fluid may help limp it along for some time, but eventually it'll give up the ghost. Problem with the manual transmission cars is when either diff fails (front rear or center) you basically get no drive in either direction.

Well now that you changed the oil now you know more or less whats going on...Silver an dark grey is not good...but I"ll go with what I said earlier-pinion bearings-they do get the worse of the abuse & if it gets low on oil it"s the 1st one to go dry...good luck

[1 Lucky Texan]

seems to me, the 'sparklies' must be aluminum. Otherwise, seems like they'd be on the magnet.

 

so, would this mean something is out of position and rubbing on the case? what's the most likely scenario for that?

[Fairtax4me]

Ever drained the gear oil out of a manual trans with a bad main shaft bearing? It comes out greyish black and full of silver swirls. It's not aluminum, the particles are so numerous not all of them get attracted to the magnet. Most of them end up settled in the bottom of the case like metal sludge. Magnets are useful, but the magnetic field only reaches so far, they can't pick out everything.

[ivans imports]

wheel berrings