guzzijohn Posted December 9, 2014 Share Posted December 9, 2014 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 Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted December 10, 2014 Share Posted December 10, 2014 A bit of play in these isn't a big deal. Why was the right side axle replaced? Split grease boot? Rear axles aren't known to fail on these cars, but since you have a replacement axle on the right side of the car I would suspect that one first. Aftermarket axles get a bad rep here for a good reason. Quote Link to comment Share on other sites More sharing options...
Bushwick Posted December 10, 2014 Share Posted December 10, 2014 I'd look at the tires, as well as the strut assembly. Raise car, check the struts. Check where they attach at the fender well for excess rust, rotting, etc. Carefully inspect the rear crossmember. My 95' Legacy Wagon had it's rear crossmember completely free floating and not even attached to the body anymore when I purchased mine @177k miles. The metal is thin and stamped out. Once it rusts, it's only a matter of time before it needs replaced. The top of the crossmember is a snow/salt trap, that isn't easily washed off from normal driving and needs rinsed periodically. Look at ALL the points where the crossmember connects to something and it's bushings. Check the rear control arms as well. Also, with the rear of the car raised, check the rear stabilizer. Make sure it's still attached at all points and make sure the end links haven't snapped. The rear crossmember has 4 body points it bolts through and 2 more on the pumpkin. Check those spots carefully that they haven't snapped or rotted out. Also, inspect the mount at the rear the pumpkin cover attaches through. It has 2 bolt studs. The bushing can fail. Quote Link to comment Share on other sites More sharing options...
guzzijohn Posted December 10, 2014 Author Share Posted December 10, 2014 Thanks Bush,interesting ideas. I put her on 4 jack stands and ran in gear(5th)and heard nothing. Looked for rusted/broken suspension or mounts and all seems fine. Took it for ride-2mi+,up over 50-NO NOISE!!?? Do I need an Exorcist? Quote Link to comment Share on other sites More sharing options...
xdeadeye1 Posted December 10, 2014 Share Posted December 10, 2014 Maybe somebody was in the trunk.. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted December 11, 2014 Share Posted December 11, 2014 if the rear hubs have also been submerged - maybe a wheel bearing is going out? Quote Link to comment Share on other sites More sharing options...
heartless Posted December 11, 2014 Share Posted December 11, 2014 if the rear hubs have also been submerged - maybe a wheel bearing is going out? wheel bearing wouldnt produce a "knocking" sound that is being described... growling, squeaking, or grinding - yes... I would inspect all suspension bushings and mounting points very closely - it is possible there is a worn/torn/damaged bushing that, under the right conditions, is causing the knocking. Quote Link to comment Share on other sites More sharing options...
Bushwick Posted December 11, 2014 Share Posted December 11, 2014 You say it clunks, then raise it up (extending the struts fully as the tires drop and body raises), lower and sound goes away, only to return later, seems it would point to something that's affected by raising the car. It's probably the struts then or something on/in them failing. The road noise could actually be a blown out strut that can't dampen the spring anymore. I've seen cars going the road with completely wasted struts and the rear wheel is bouncing so quickly, it looks like it's going over whoops on a dirt bike track. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted December 11, 2014 Share Posted December 11, 2014 do you 'feel' it or just hear the sound? Quote Link to comment Share on other sites More sharing options...
guzzijohn Posted December 11, 2014 Author Share Posted December 11, 2014 (edited) just hear it. The crazy part is having it quit. That last drive included blocks of bumpu rutted ice that surely should've aggrivated it into banging again. Edited December 11, 2014 by guzzijohn Quote Link to comment Share on other sites More sharing options...
guzzijohn Posted December 11, 2014 Author Share Posted December 11, 2014 Just surfed this site a bit more for clues. Do any of you think this could be center differential? I don't hear anything at the back of the traneaxle but if it were to give the rear a different speed of rotation who knows what can happen? Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted December 11, 2014 Share Posted December 11, 2014 (edited) that's why I asked about the feeling. One test for torque bind would be tight circles on level dry pavement. If you can't idle thru them or , maybe , get trhu them at 1K rpm without feeling some bucking/jerking - you may have an issue withthe AWD system. have you tried swapping wheels front-to back? Inspected the swaybar endlinks? Check the lug nuts/studs, check the axle nut, etc. Edited December 11, 2014 by 1 Lucky Texan Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted December 11, 2014 Share Posted December 11, 2014 I don't think a rear diff would knock. Since it seemed to stop after raising the car it could be strut related. Are any of the struts leaking? The wagons have relatively easy access to the upper strut mounts. You might make sure the mounts are not damaged and the upper nut on the strut shaft is tight. Quote Link to comment Share on other sites More sharing options...
guzzijohn Posted December 11, 2014 Author Share Posted December 11, 2014 I'll try the circle thing. Quote Link to comment Share on other sites More sharing options...
jonas Posted December 13, 2014 Share Posted December 13, 2014 I like the thread title. 1 Quote Link to comment Share on other sites More sharing options...
Bushwick Posted December 13, 2014 Share Posted December 13, 2014 (edited) Did you confirm the struts were OK? If you still can't diagnose it, take it to a local Good Year or something (I semi-trust their mechanics as at least being honest, especially if when they caught something I didn't, but they are WAY to weary to do some things like reset an air bag light ) as I believe they still do "free inspections" and should be able to confirm the issue. Then come back and talk to us for any advice or clarification if needed. The rear crossmember was fairly easy to do, despite 50% of literally being "gone". The stuff I threw out was the handful of things from memory that appeared to be able to make noise if in a bad enough state of disrepair. IF the pumpkin housing where it bolts through the rubber bushing in the rear crossmember, where to be allowed to float freely and no longer be tied to the crossmember, I suspect it'd be difficult to diagnose. After seeing what was left of the old crossmember, it made me wonder how long it had been rotting like that to even get like that. Not kidding, there were huge chunks off the top area completely gone. It's ironic though, as this was the reason the previous owner's son (he was in his 40's) was essentially forcing his 70 something year old mother to sell the car as she had apparently been driving it like that for sometime before saying anything to him, and he figured she probably shouldn't be driving anymore as it definitely wasn't safe. Even better was no one wanted to buy it from them which allowed me to get a super running Legacy (albeit with some rust and garage door frame paint scuffs) for an excellent bargain. So, either look more closely at the struts, crossmember, stabilizer bar c-clamps, end links, etc. and find what's broken, or try and let someone diagnose for free. Hopefully the top strut mounts on the wheel wells are still solid. Oh yeah, is yours a wagon? Have you ruled out the rear hatch? Mine started making some noise that sounded like a squeaky chassis or dry suspension, and even appeared to be coming from outside the car at low speeds. Pushed down on the bumper and the rear hatch was making it on the passenger side. One other thing that dawned on me just now, have you inspected the exhaust? A missing or rotted rubber hanger could allow the pipe or muffler to drop just enough that it's clunking on something. I'd say the muffler bumping under the rear bumper area would make the banging noise, even worse if a strut was bad as the entire wheel will move violently up/down, which would exacerbate other noises like a muffler bumping. Have even seen corners on catalytic converters bump trans tunnels at highway speeds making a hard to diagnose bumping up front. Pair of vice grips bending the corner tabs down took care of that in another car. Edited December 13, 2014 by Bushwick Quote Link to comment Share on other sites More sharing options...
guzzijohn Posted December 13, 2014 Author Share Posted December 13, 2014 I just did several dozens slow circles both cold and after driving several miles and nothing. The last 2 times it occured was right away when cold and didn't stop. Now 2 test runs w nothing. I'm still thinking the center diff. but I seem to read that should get worse w temp. increase. Can torque bind come & go like this?? Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted December 13, 2014 Share Posted December 13, 2014 (edited) unless you were running a donut spare or different sized tire, it's not reported as a 'come$go' type of issue - the 5pseeds are often reported as being worse after they heat up. symptoms get worse over time. It stresses the entire drivetrain of course and worn-out/broken parts elsewhere could exhibit problems - wherever the weakest link is - carrier bearing, u-joint, half-axle/CVJs, etc. if it seemed like it was worse on one side than the other, might be useful to swap axles L to R. just, really, doesn't seem like TB. I'd think you would FEEL the stress buid-up/release/build-up/release, etc. is the banging started or solved by brake application? Have you tried lifting the E-brake handle to see if the sound is affected? are the pads on the rear brakes evenly worn? inside pad material not worn a lot more than the out side pad? I only read a lot, others here have the real experience. Edited December 13, 2014 by 1 Lucky Texan Quote Link to comment Share on other sites More sharing options...
guzzijohn Posted December 13, 2014 Author Share Posted December 13, 2014 Brakes were the 1st thing looked at-no issues or effect on banging. Bad bearings,broken gear teeth,loose bits don't heal themselves. I'll try again when temps drop-mini hearwave now-40s. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted December 13, 2014 Share Posted December 13, 2014 the rear diff's drain plug has a magnet on it - you could look for 'chunks' I guess. 1 Quote Link to comment Share on other sites More sharing options...
Bushwick Posted December 14, 2014 Share Posted December 14, 2014 A damaged rear diff wouldn't come and go. Usually when a diff goes, you hear a loud BOOM. It might still be driveable at a slow speed, but it'd definitely let you know it was shot. The chunks that that break, then get tossed into the ring and pinion and cause further damage. If a c-clip (or whatever Subaru uses) where to snap, you'd get the same deal. IF the carrier was loading left/right, you'd get varying degrees of gear whine as the teeth wouldn't be meshing correctly. No offense, but you've had a couple people say look at the struts, and I'm suggesting that or your crossmember has issues, along with a few other symptoms that WILL make noise. Have you actually ruled them out yet? Quote Link to comment Share on other sites More sharing options...
xdeadeye1 Posted December 14, 2014 Share Posted December 14, 2014 Just throwing this out there.. if the banging were in time with the wheel rotation,, maybe something broke off banged, a few times then totally broke off,, now no more banging... like perhaps the gear teeth of the ABS? or something else along the lines of where the wheel mounts. Quote Link to comment Share on other sites More sharing options...
MilesFox Posted December 14, 2014 Share Posted December 14, 2014 parking brake shoes: check to see that they didn't fall out. Quote Link to comment Share on other sites More sharing options...
Loyale 2.7 Turbo Posted December 14, 2014 Share Posted December 14, 2014 (edited) the rear diff's drain plug has a magnet on it - you could look for 'chunks' I guess. That is good idea, sometimes a differential broken a small portion of a teeth, which could make interference between the rest of the gears, untill it is grinded, So, it worth check the Differential; especially after reading this description of the Noise: ... hearing a mild hollow knock that matched wheel rotation frequency. ... Kind Regards. Edited December 14, 2014 by Loyale 2.7 Turbo Quote Link to comment Share on other sites More sharing options...
guzzijohn Posted December 14, 2014 Author Share Posted December 14, 2014 (edited) The thing is that it has come & gone several times. I will check plug-I had changed gear lube last month. Edited December 14, 2014 by guzzijohn Quote Link to comment Share on other sites More sharing options...
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