2000 Outback H6 driveline vibration

[RodA]

I'm running out of ideas to fix a persistent vibration in my auto H6. 

 

Symptoms are:

 1 Occurs at various speeds, most noticeable above 40kph.

 2 Putting it in neutral does not seem to help, though perhaps a little.

 3 Vibration is reduced when under load or accelerating.

 4 Whole car vibrates, but not severely, can't locate source.

 5 Unaffected by engine speed.

 

What I had done:

 1 Reconditioned transmission installed a year ago and seems very good. Oil levels good and clean.

 2 Tailshaft balanced and U joints replaced.

 3. New front and rear wheel bearings.

 4. Used rear diff installed.

 5 New aftermarket front driveshafts.

 6 New front control arm bushings and ball joints.

 7 New front sway bar D bushings and new sway bar links

 8 New front struts.

 9 New front strut top bearings.

 10 New rear bushings for rear upper control arms

 11 New tyres and 4 wheel alignment.

 

Any ideas?

Rod

 

 

[GeneralDisorder]

Get factory Subaru front axles for it. Aftermarket are know the cause vibration issues with the 2000 to 2004 models.

 

GD

[CNY_Dave]

If the wheels have very hard corrosion built up where they meet the disks, it can give a vibe that is impossible to wheel-balance away.

 

I literally had to take a flat-ended round punch and put it on the corrosion and tap the punch with a hammer to get rid of it.

 

If there is a lot of crud on the disk, on the side facing the wheel or the side facing the hub, can do same thing.

 

With that type of vibe, it can be very subtle until 2 or more wheels 'sync up'.

[CNY_Dave]

Get factory Subaru front axles for it. Aftermarket are know the cause vibration issues with the 2000 to 2004 models.

 

GD

 

Was vibe at idle in drive a good indicator of that condition?

[GeneralDisorder]

Was vibe at idle in drive a good indicator of that condition?

Yes generally speaking. He mentions aftermarket axles so figured it couldn't hurt to mention the problems those usually have. Might not be his whole issue though. 

 

GD

[RodA]

I should have made it clear that almost all the things I have done were done after the vibration started, in an attempt to alleviate it. Only the front wheel bearings and bushings were done earlier. Changing the front axles had no affect on it.  Also, there is no vibration from the engine, or at slow speed, say below 30mph. Revving the engine at speed while in neutral has no affect, nor does using a different gear. Only the usual Subaru vibe at idle in drive.

 

There is no significant corrosion on the wheel hubs or inside of the wheels. I've cleaned those areas anyway. This is a Mediterranean climate here, so rust is not much of a problem. Changing the wheels around has no affect. 

 

Perhaps it could be the rear driveshafts, but they seem fine with little slop. I was thinking of making a video of them from underneath while driving to see if they run true.

 

Rod

[1 Lucky Texan]

seems like a remote chance but, I didn't see carrier bearing on the list.

 

is there any noise with the vibration? feel it in the steering wheel or 'seat of the pants'?

Edited March 19, 2017 by 1 Lucky Texan

[GreaseMonkey03]

How are the motor mounts?

 

Is there a noise associated with it or just vibration? Does it do anything different while turning, braking, etc.

Edited March 20, 2017 by GreaseMonkey03

[RodA]

Thanks for the ideas. The car was running increasingly rough in the last week or so, which made the vibration much worse. So yesterday I did the arduous task of changing the plugs (and using an injection cleaner). Engine is now silky smooth and the vibration is much reduced, though still there.

 

No real difference with turning or braking. No noise either other than the shaking making the cabin trim vibrate.

 

Part of it might be the rear bushings of the rear diff. When I replaced the diff, I could see one of the bushings was shot, but I could also see that it would be a major pain to remove and replace them as the carrier seems to be welded to the body. I did some research and ordered the the Whiteline KDT927 bushings that can be pressed into the gaps from the rear. This might help. Should have them in a few days. Agreed that the vibration may be due to slop in the drivetrain mountings as it goes away under load or hard acceleration. It's of the order of a few hundred hertz at a guess, mostly felt in the seat and body, very little in the steering.

 

It's most obvious on the level at constant speed or going downhill at 20-40 mph, also around 60 mph, not a simple increase with speed.

 

Update: the Whiteline bushings arrived today and I put them in with high expectations, but the reverse happened - the vibration seems to be much worse now! The new bushings are pretty stiff, so it seems that the old half broken ones were absorbing vibrations rather than causing them.

 

I checked that the rear wheels and tires spin true.

 

More background: the car first developed vibration at speed about a year and a half ago and I correctly diagnosed the tailshaft. The U joints were worn out so I had them replaced and the shaft balanced. This completely fixed the vibration. The new vibration started about a year later with similar symptoms, so I took the shaft back and they did a very minor rebalance for free, and we checked that the U joints and centre bearing were all ok. However this had no effect on the car, and despite all my fixes, the vibration has steadily gotten worse.

 

Running out of ideas here...

 

Rod

 

[ferret]

Few things come to mind reading this thread, so I will add my experiences. Could solve your problem or give you more to check into.

 

You mentioned replacing the rear differential AND you have an H6, so I would be certain you have one with the proper gear ratio. IF not, this can cause a lot of different issues I have seen. IF the ratio was CLOSE, the car was drive-able, but above 25 mph or so, the trans went crazy trying to engage AWD and cause strange stuttering from tires scrubbing. This was obvious knowing the rear was just replaced, and checking the numbers to find the WRONG gear ratio.

 

Also my 2 experiences replacing STAKED IN U JOINTS were NOT good ones ( 98 Forester Auto, and 04 Forester 5 speed ). Both times I had a local shop TEST and Balance the shafts, but each had vibrations starting about 45 mph and got progressively worse. I finally replaced them with used ones with lower mileage and from cars that were not crashed too badly as to damage the center drive shaft.

 

My experiences and thoughts...... good luck..... just bought and fixed a 2001 outback 2.5L for our daughter in Pittsburgh last summer, She loves it.

[RodA]

The replacement differential was definitely from an H6. It didn't improve the vibration, but did fix a slight gear whine (60k vs 240k miles). The shop that fixed the tailshaft was the only one in town that could do staked U joints, and they have a long history of doing such. As mentioned, it completely fixed the original vibration when the U joints were obviously bad, and when I took it out a year later, the joints seemed like new. They dynamically rebalanced it by tack welding a small washer on the tube, so it was very minor. So it seems possible but unlikely to be the problem.

[1 Lucky Texan]

if you swap tires around - any change? Rims OK and straight?

 

if the car were on 4 jack stands and run, would it still vibrate?

 

just thinking this 'might' help point towards bushings/axles/brakes - vs, engine transmission drive shaft. because some components would still receive 'close' to typical stress, while others are spinning mostly stress-free.

 

I know it's a longshot/oddball idea, but it is cheap to try

[CNY_Dave]

Where the driveshaft goes into the transmission there is a sleeve bushing in the trans.

The nose of the driveshaft turns in this bushing, if the bushing or the nose of the driveshaft are worn it could get a bit out of alignment and vibrate, might only do it sometimes.

Can probably be checked simply by attempting to angle the front driveshaft piece that goes into the trans.

If this is a problem, the vibrations would to a degree be sent down the driveshaft and into the rear diff, and would be more noticeable with stiffer diff bushings.

 

Putting in the FWD fuse make any difference? (Long thread, did we ask that yet )

 

Here's an idea- put a hose clamp on the driveshaft, this will throw it out of balance.

Does the 'cadence' of that vibration, and how it changes with vehicle speed (at about 4x driving speed) seem similar to the vibe you are chasing?

[RodA]

Thanks for the idea of a hose clamp on the driveshaft. I'll try that tomorrow. Don't think the the front of the driveshaft is worn - looked fine a few months ago when I had it out. I can't put the car in FWD only. There is no fuse location for that - early H6 models sold in Australia didn't have that option.

 

I have long thought of putting the car on blocks and running it to observe the vibration, but it seems risky as the car would need to be supported by the suspension arms so driveshaft angles are normal, and I wouldn't dare get under the running car in such a situation. Maybe a GoPro video makes more sense.

 

There is no clear relationship between the frequency of vibration and road speed. It seems fairly constant, though it may go down a bit at low speeds.

[RodA]

I made a video showing parts of the tailshaft and right rear driveshaft as I drove on the freeway, and they ran true at all speeds. I don't think it is the rear shafts. I had also inspected them by hand when I did the rear bearings, and they seemed good. They don't get subjected to the angles that the front shafts do of course.

 

I've since had a shop put it on a hoist and run it and the rear transmission mount was clearly stuffed - it was in two pieces actually. There was also some run out on the left front driveshaft (that I replaced a month ago) as well. Wheels all spun true. I had the transmission mount replaced, and this improved it a bit, then I put in a new third party front driveshaft and this improved it more, especially at speeds below 50 mph.

 

Still, the vibration is quite noticeable at higher speeds.

[Stoner Dude]

RodA,

Did you leave the original shot bushing in place when you installed the KDT927?  I am doing this now and the inserts seem way to big to fit into the voids if i leave the original bushing in place.

thanks