emergency! wheel/drive axle bounce?

[bosango]

Hey there Subies,

 

I've just limped into Ely, NV with some sort of driveline problem. A month or so ago, I noticed a slight shake coming from the rear of my 1993 Legacy LS. It felt like the shake you get when a wheel is out of balance. Not being a big deal, I let it go (in retrospect, that was probably a bad idea as these things never get better over time). Well, tonight on the highway it went from barely noticeable to practically undrivable at anything over 35 mph as it was shaking so bad. My friend, who thankfully was following me, said my left rear wheel appeared to be bouncing. I pulled over and checked out what I could, but I couldn't find anything obvious: no bulge in the tire, nothing appearing overly loose, some play in both drive axles, but not extreme. Of course, it was dark and the underside was full of mud, so I may have missed something. On a long downhill I shifted into neutral and the bouncing was still just as intense.

 

So, could a tire that's badly out of balance cause such violent shaking? Could it be u-joint or drive axle related? In the morning I'm going to put the spare tire on and see if anything changes. Depending on the cause, I think my repair options might be rather limited here and there's bound to be a wait for any driveline parts, so any advice on where to look first would be extremely helpful.

 

Ely's a nice place, but I'm not looking forward to an extended stay here. Thanks in advance for any and all help!

[ericem]

I don't think it's a axle. My axles have some play very very minimal though i mean in the rear. I would assume it is the wheel or the hub itself creating the issue if you can indeed physically see the rim not rolling square.

[broncolouie]

I am thinking either strut problem: not dampening or broke mount or seperated belt in the tire. just guessing. Hope you get it fixed and don't get stuck for too long.

[mr.radon]

Sounds like no damping.

[MilesFox]

you mentioned mud under the car. sounds like you have mud packed in the rim, which will throw off the balance of the wheel. the mud was probably evenly distributed, and some of it broke away, leaving a lopsided chunk inside the wheel, and progressively threw out the balance as it broke up.

[bosango]

Turns out, embarrassingly enough, it was just mud on the rim. I've never had alloy wheels before, so I've never had to deal with that. The dampening thing is something I'm going to look into when I get back home because there's been something loose back there since I got the car a few months ago. I should probably have the balance checked, too.

 

Thanks for everyone's help!

[mr.radon]

Watch out in the winter. If you park next to a curb I've gotten a ice wedge frozen on my passanger side rims, undrivable above 20mph. No way to get it out either. That sucked...

 

Also, if your rear shocks go, you can quickly scallop tires by the undampened bounce. Pretty pricey to let that go, new tires and new shocks. I paid for that mistake once.