Nasty clunk up front

A couple weeks ago, a friend asked me for an assist in diagnosing a clunking sound that started suddenly in his '97 (or so) Legacy. Automatic transmission. Definitely rotational, one clunk per wheel rotation. Bad enough to make the car undrivable. Passenger side.

 

Not having seen it, I figured a bad tire.. tread separation, amplified by a bad bushing or something. well, no.

 

Yesterday I met with him to have a looksee, and sure enough, it ain't a tire. And sure enough, I would not drive the car. It's loud. Only other observations: It mostly goes away during a hard (full lock u-turn), and it completely goes away when you throw it in neutral and let it coast. Tried reverse, no noise.

 

Any event, back at his house, jacked it up and pulled the wheel. Can easily reproduce the noise by turning the hub fore and back to its stops. And can move the inner part of the CV joint up and down way, way more than should be able to. Of course, can't tell if that movement is in the CV joint, or if the axle shaft is moving too.

 

So, it'll first be 'out with the CV joint' for diagnosis. Hopefully find that it was just a bad rebuilt unit that got installed within the last couple years. (and very few miles). If it is the CV joint, it'd be the inner part inside the 'can' shaped housing, which I presume is not what usually fails in a CV joint.

 

Otherwise, it's in the transmission (again, automatic)...well... differential. Is there a bearing that supports that axle? If so, can it be replaced in car?

 

Second, if it does turn out to be the tranny/diff assembly, and it can't be fixed at home, what are your thoughts on putting the whole lot back together without a CV joint and running it as a RWD car temporarily? I presume we'd have to figure a way to keep oil in. But are there other risks? A new-used transmission/differential has been sourced, but that's more of a job than we're up for.

 

Only other item of interest, both transmission and differential fluids look fine. Clean, not low, and no shiny metallic bits. So, of course, we're really hoping to find it's the CV joint.

 

Sorry this kinda got long for what will be a pretty simple diagnosis. We're just not familiar with Subarus (though we have both done CV joints in our Legacies )

 

Thanks for any insights!

Matt

I had a similar issue with my wife's automatic lgt. It was a bad wheel bearing, and cv axle. The wheel bearing was so bad that the hub fell off when I removed the axle nut to replace the axle. Since it was so bad, it created a sticky spot in the rotation which damaged the inner axle joint from the jolting. The wheel was trying to stop but the axle was trying to go.

 

I thought for a while that it was a trans issue too, luckily it was not.

Most of them will have a little play in the front diff side bearings or where the axles go into the trans and if this were to be the problem you can't replace any diff parts with the trans still installed. What's weird is you say the noise goes away if you throw it in neutral while driving. I would think if the diff is bad it would make a noise when ever its being rotated and more noise when a load is being applied. I would start looking towards the axle. If you replaced it the part should have a warranty, in fact almost every axle now days are a lifetime warranty from auto parts stores. The other things it could be, axle like I said already, brakes, wheel bearing or the worst thing the trans. Far as pulling the axles to make it rwd only this won't work because the power split is 80% front and 20% rear. So the car wouldn't be able to drive very fast if at all. GL. Can you post a vid of the noise with the car totally off the ground and the wheels spinning. This is how I always diagnose rotational noises. Easier this way. If you think it's the diff I would drain all of the fluid out and look for chunks of the ring gear and or pinion gear.

Thanks both! I'd loved to have been able to put the car entirely in the air... but don't have that equipment. Indeed, I should have grabbed my camera for video.

 

Any event though, I'm certain its that inner CV joint or in the diff. I, too, was surprised when it went away in neutral.

 

The play I mentioned in the side bearings is minimal on the drivers side. It's WAY bigger on the offending passenger side. It'd be nice to get pics of the damage, whatever we find. But unfortunately, assuming it is the CV joint, yes.. it'll have to returned for a warranty replacement.

 

But damn, I'm curious

Equipment? All you really need at least is 2 jackstands and a jack but 4 stands were be much more safe. Can you borrow a couple or whatever you need? Just trying to help you figure out your issue.

The noise goes away in neutral because the axle has no torque being sent through it. When power is sent through a loose joint it chunks when the rest of the axle catches up

Equipment? All you really need at least is 2 jackstands and a jack but 4 stands were be much more safe. Can you borrow a couple or whatever you need? Just trying to help you figure out your issue.

 

Totally get that Spooln.. and indeed, Thank you! And yes, of course extra jack stands could be procured. Problem is steep driveway, and lots of chillins running around in the neighborhood which probably already frowns on any manner of car work, let alone 'putting a car on blocks in the front yard', if only for a couple minutes.

 

We'll know what's going on when the axle is out, and if it's not the CV joint, the car will need towed anyhow, so there won't be any need to re-install said axle.

 

We'll definitely post back when we know what's going on.

I'm not on location, so I've not seen what's going on first hand.

 

But Mike pulled the CV joint this afternoon. Lo and behold, it seems the axle came out with it. That is to say, the short axle that fits in the transfer case on one side, and fits into the CV joint on the other.

 

Hard for me to believe that a simple circlip would hold that axle in there, but maybe. And if so.. well... ???

 

At this point, I'm at a bit of a loss.

 

In case attached pics don't work, there are here:

http://i.imgur.com/IK9u9d1.jpg

http://i.imgur.com/cr8WFDD.jpg

 

http://i.imgur.com/IK9u9d1.jpg

 

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http://i.imgur.com/cr8WFDD.jpg

 

Huh...

This is the guy with the 1998 Subie. Just wanted to add that the wheel bearing feels smooth and all bushings & such are tight. CV Joint seems to feel normal.

Yeah, the clip is what holds the axle stub in. I've heard of alot of ppl pulling them out by accident trying to replace a half shaft. Should just pop back in seeing as the spring clip is still on the end.

 

The manual transmissions have the circlips that take pliers to remove I believe. And I could be ass backwards as my 4eat knowledge isn't the best.

 

Maybe the diagram below will help show what i mean about them just popping in and out. Good luck, LT.

Yes. It just pops back in. Get it lined up by hand then tap it with a rubber mallet until it pops into place. Be very gentle and straight inserting it initially, as not to damage the seal.

Did he remove the spring pin that holds the axle to the stub?

I always pull the whole lot out. Can't be bothered banging out that tiny rod. It comes out and goes back into the trans ax no trouble at all. Only one side has a clip on it anyway. Why one does and one doesn't, I have no idea ? Mitsi's the same.

Initial bench inspection of the U-joint didn't reveal any problem with the CV joint. I was not content with that, so insisted on a more thorough inspection. Indeed, at a glance, it felt pretty okay. But chucking the axle in a vice and torquing on things, there most definitely was some play in that inner joint. And most prominent when the joint was in normal driving position, that is, pretty much straight.

 

I'd hoped to find something more obvious, but it was convincing enough for the folks at the parts store to honor the warranty and replace the whole lot. We're thinking perhaps the binding of that joint pulled the stub axle out a bit, such that between a floating stub axle and the binding joint, what was a minor binding issue was compounded into the nasty rotational clunk. (there was zero resistance when that stub came out with the CV joint)

 

Any event, stub axle clipped back into place, new CV joint in. Now just waiting on a new hub to replace the one that had a sheared wheel stud. Hoping for the definitive test drive later today. Will hopefully be able to post positive result after that.

 

Again, thank you all so much for the help!