Need help isolating vibration/shudder at highway speeds

95 legacy wagon 2.2l automatic

 

 Ive been diagnosing a high speed vibration for awhile. Its generally not felt in the steering wheel so much as it is felt through the whole car. Initially changing the brake calipers out had helped, as one was stuck and the rest in various stages of getting stuck. Initially that worked for a fee hundred miles... Checked the calipers again, one was stuck again, replaced it. Went away for a couple hundred miles, came back, the calipers are fine this time. Even wear on the pads(all replaced as well).

 

Ive since done an alignment and replaced all the tires, balanced etc. The rear driver side is scalloping on the inside tread, so i rotated the tires and that didnt solve anything...

 

So the back struts are dead for sure, i get no play or feed back in the spring when i check for bad bearings... The differential has began seeping, but nothing alarming as far as rate. No odd smell of burning up the rear diff. But the seepage seems to be coming from above and around the other side of the fill plug... There is no oil on the axles what so ever.

 

The bushings are 50\50. Axles look, feel, and sound fine. I cant really identify a specific noise while driving, as in humming, howling, growling, grinding, but it does seem road noise is loud(er?)

 

Am i dealing with shitty struts, can i overlook the bearings, should i be trying to check the drive shaft or rear diff

 

Is there something i can do while its on 4 stands to check? Ive read other threads recently posted but im not sure my front is to blame as it feels like its in the rear.

 

It doesnt really care if im turning to the left or right, tight turning is still responsive(i think. Ive never had an awd, so maybe i dont understand what torque bind is etc), no clicking. Its seem to be more prominent at higher speeds, above 70mph, seems to be better when its cold or dark outside(weird?), but once it starts i can feel it all the way back down to 30-40 mph.

 

Idk. Thanks for any insight.

If you can make it really secure up on stands to where you can 'drive' it at speed, if it shakes at speed with the tires off the ground, the problem would likely be in the driveshaft or carrier bearing, if nothing, then I'd suspect used up struts and a bad bushing. The same as is messing up that one tread. I think I would chase that first since you said the vibration hangs with you back down to lower speeds once it starts. That makes me think of too much undamped compliance in at least one wheel.

Okay. So just 'drove' it on stands, couldnt pin point anything in the driveshaft area, buuuut i noticed my rear 2 tires do not spin. Fwd fuse is not in.

 

Is my diff locked up?

I don't have the 4EAT, but I would say that the solenoid that controls 2/4 is stuck. If you have lots of time and want to do everything yourself, make a remote wired switch that you can put into the fuse holder so you can be under the car with a stethescope while you switch it. Listen to the trans for anything to happen in there. Switching should make some kind of noise in there. You could also probe the contacts on the solenoid connector and see if it is burned out or something.

 

It's hard for me to imagine the center diff being so burned up that the back wheels don't move at all, but like I said, I'm not experienced with the 4EAT.

 

I believe the center diff can be swapped with the trans in the car, but again, I might have that wrong...

 

But the results of your test make me think that rear driver's wheel system is in trouble.

 

I had a terrible shimmy in the front of an 82 GL that had been parked for nearly a decade. The struts were completely done, so I just went slow while I got it home from where I got it and put new struts in. That was enough damping to fix the problem. But if there are bad bushings, fixing those as well would be the ultimate goal.

I believe the center diff can be done with the trans still mounted, from what i understand the 4eats have the clutch packs and all at the rear where it connects to the driveshaft... But ill research more...

But i wonder if its the rear, because it has worked since i got it, ive taken this thing through some weather, but a random seepage has developed at the rear diff.

But i think yes for now perhaps ill get these rear struts changed out and do those bushings, im debating on slappin some axles on em too while im down there.

I don't think it would drive if the rear diff was in that much trouble.

 

Turn the driveshaft by hand where you can reach it just in front of the diff and see if that turns the rear wheels smooth and quiet. If the center diff engages again, that will be pretty difficult to do, but if the center diff is open, then it should turn pretty easy.

I don't think it would drive if the rear diff was in that much trouble.

 

Turn the driveshaft by hand where you can reach it just in front of the diff and see if that turns the rear wheels smooth and quiet. If the center diff engages again, that will be pretty difficult to do, but if the center diff is open, then it should turn pretty easy.

 

So it turned relatively easy. But one of my tires could spin freely, the other was getting held up mid way thru its rotation. So i pulled the tired off and checked the caliper to make sure it wasnt sticking... It was, but i unjammed it and now it glides free, it still has difficulty spinning freely thru its whole turn. Noise souns like its coming from the opposit side of the rotor from the caliper, but in the back side of the spindle...

 

So... As far as the drive shaft spinning smoothly and easily, what does that mean?

As for the other thing? Bearing or axle?

Probably wheel bearing for the noise at the wheel. That is a fairly big job to do and will need a press.

 

The driveshaft turning easily goes to the center diff being stuck open or burned out in a 5MT, but in the 4EAT since things may disengage when it isn't running, I'm not sure if that is conclusive. If there are no hydraulic clutch packs between where the parking pawl grabs and the center diff, then the center diff would be bad or otherwise opened. If there is a clutch pack between those points then the test would be meaningless as it would turn freely because that clutch pack is disengaged.

Found another threat about the center diff and 4eat...

If its not the solenoid then i can just swap the rear housing with a good unit and it will work. Basically the same if im understanding... Guess ill get on it. Thanks for the help.

Any other thoughts or suggestions would be cool

I'd get that rear corner straight first. Otherwise it may eat tires. And the vibration, if it gets bad enough can reduce traction. Like how you can't hit the brakes hard going over railroad tracks.

I'd get that rear corner straight first. Otherwise it may eat tires. And the vibration, if it gets bad enough can reduce traction. Like how you can't hit the brakes hard going over railroad tracks.

 

Ill be changing bearing/spindle, bushings, axles, and struts in the rear tmrw/weds... Ill diagnose awd after the weekend and just throw the fwd fuse in the box.

Sweet. I hope it goes as smooth as the SVX bearing I just did.

Sweet. I hope it goes as smooth as the SVX bearing I just did.

 

Should be. Found a 96 legacy with a new axle nut and behold new bearings... Whole assembly spindle and all is 25$ a pop. Struts are decent so im gonna go back tomorrow and pick them up. And i got some axles in the meantime. And if those axles are still good ill probably just repack them and reuse them or resell.

All i need is to get bushings for everything in the rear.

Wondering if there is parts number list for the bushings specifically in the rear so i dont accidently get the wrong ones.

I got my suspension rebuild parts from https://www.suspension.com/products/subaru_legacy_1995

 

Looks like they still have them, but these aren't OE parts, they are poly so they are stiffer than OE. It's hard for me to say how much stiffer because I did struts at the same time, and the old struts were very done. I do like mine very much. Stiff enough to be a little more sure footed than before without being harsh.

Cant say for sure exactly what the vibration was, but after replacing the rear bearings, axles and shocks, it had indeed dissapeared.

Its hard to say if it was the bearing, because the side i suspected spun quietly, with a little bit of the resistance i was feeling turning the DS by hand. the other side spun freely but was very grindy. So i guess it was the bearings, but i did everything to be sure. and i am not sorry i did that...

I expect it was the strut. I've had such a terrible vibration on two different cars that had all solid parts except the strut was totally done. But then those were both front wheels...