vibration at 20mph... probably bad CV... anything else?

[yarikoptic]

Hi All Subaru People,

 

I have a problem which I've been trying to diagnose but had no chance yet to try to fix (inclined weather conditions forbid me going under the car on the street :-/). Following the information I've collected it seems to be a right CV joint, but I can be totally wrong, so if there is anything else (my be problems in differential/AT?) which could describe my car's symptoms, please mentione them so I could check for them whenever I get under the Subi. Here is my compilation from a tiddlywiki where I keep my notes:

 

!Problem

I have a problem: you can feel vibration while accelerating at speeds 15-23 mph. Specifics:

* is not present at speeds not in the mentioned range but might be linked to light 'whom-whom-whom' sounds at 35-45mph (usually after coming from highway speed down to city-speed)

* occur also in FWD mode

* seems to be absent while cruising (without acceleration) at the problematic speeds.

* seems to be only at acceleration. I didn't feel it while going at the same speed down steep hill so the load might be similar but in opposite direction. Most pronounced at a "good" acceleration. Too fast acceleration passes range of speeds to fast to mention much of vibration ;-)

* seems to be coming right under the driver seat, ie in the middle of the car, but I can't be definite about that... may be from front ;-)

* seems to decrease when car is loaded (driver+2passangers). So either increased mass absorbs more of vibration (which is less probable) or may be it is indeed CV joint of which is gets in other position with car sited lower

* seems to be not as prominent (or even absent) when driving not yet warmed up car

* seems to don't depend on the gear (tried in 1st)

!State of the mechanism and changes which didn't impact vibration:

* AT was flushed recently

* CV joints:

** left one was recently changed

** right one visually alright but who knows

!What it is not probably

* it is not tires which were balanced recently and since it occur only at acceleration. Although it might be the cause of premature tires going out of balance. Only after 400miles from previous balancing I start feeling wheel vibration at 70mph

* it is not a propeller shaft/rear driveline since it occur in FWD mode (when it should not be loaded) as prominent as in AWD

!What it could be

* that right CV axle

* Tires... [[if the radial cords in the sidewalls of a tire are not spaced evenly or are damaged, it can create a "waddle" or vibration due to force variations in the stiffness of the sidewall as the tire rotates.|http://www.aa1car.com/library/tires2.htm]]

!Findings online:

*[[Follow-up: Dear sirs, I have information that may be helpful to other Subaru owners. I have a 1999 Outback-limited wagon, automatic. I had what "appeared" to be an engine miss about 2800 rpm and in the speed range of 20 -30 mph that occurred on incline while accelerating. In reality, it was a vibration in the drive train. I had the vehicle checked at Wyoming Valley Motors Wilkes Barre PA. The fix was replacement of the front axles; the work was covered under Subaru warranty. This car had 46000 miles on it and the problem started at about 42000 miles. Please post this info in your column as it may help other frustrated Subaru owners. John|http://www.2carpros.com/makes/subaru1.htm]]

* http://endwrench.com/images/pdfs/ChaseEWAug06.pdf

* http://www.aa1car.com/library/vibrations.htm

* http://www.aa1car.com/library/tires2.htm

[Manarius]

I think it's a driveshaft U-Joint. The shaft still spins whether the FWD fuse is in or not - the rear diff spins it.

[yarikoptic]

I think it's a driveshaft U-Joint. The shaft still spins whether the FWD fuse is in or not - the rear diff spins it.

Right - it spins, but it should not get torque from the engine, so I am not sure should it vibrate as bad with torque applied or not applied during acceleration... Although it probably would get some 'back'-torque from rear diff on acceleration which would will also accelerate its revolutions back from the wheels... but it will be miniscular since there will be no load on driveshaft on engine's side.

Also there was strong effect of reduced vibration when more people climbed in the car. I was asking them to mention the vibration and tell their unbiased feeling where it is coming from. I failed to produce the feelable vibration to them...

But yes - and thanks -- indeed, I should not rule it out and check on the condition of the U-joint and its freeplay I guess, right?

[Manarius]

You also said you feel like it's coming from the middle of the car - that even more points toward it looking like a U-Joint. Trannys don't usually vibrate like that just going straight forward, but if the U-Joint is shot, the driveshaft will wobble a good deal. I can't honestly think of anything else except maybe a broken/half broken motor mount that would cause a vibration unless it was unbalanced tires or something simple like that.

[yarikoptic]

Trannys don't usually vibrate like that just going straight forward, but if the U-Joint is shot, the driveshaft will wobble a good deal.

I really hope that it is not what is happening since otherwise I guess I will need to change whole driveshaft and that will be costly I guess..

 

I can't honestly think of anything else except maybe a broken/half broken motor mount that would cause a vibration unless it was unbalanced tires or something simple like that.

well - engine vibrates at RPMs not at vehicle speed, so I think it should not be the case... may be tranmission mount though... or may be --- does subaru transmission has some weight factory-attached to compensate some vibration disballance? may be I managed to kick that off?

[pearlm30]

I also have the same problem(left CV boot tore)but after switch to smaller tires, the problem went away??? I will replace the CV axle and report back tomorrow.

[yarikoptic]

I also have the same problem(left CV boot tore)but after switch to smaller tires, the problem went away??? I will replace the CV axle and report back tomorrow.

Brr... so you have (had) a problem of vibration or a tore CV boot? ;-) I guess, vibration was gone with changing of tires, and now you are to replace CV.

Was you vibration also at low speeds and acceleration dependent?

[pearlm30]

My snow tires are smaller size than the standard outback tires. So basically went from 205/70/15 to 185/60/14.

When I accelerate(foot on gas)from about 20 to 40 mph, the vibration is felt at steering wheel and seat. Once I stop accelerate(foot off gas). The vibration stops right the way.

My left CV joint was bad and grease was all over. Will be replacing it this afternoon if the weather is warm enough.

Will keep anyone updated.

 

 

 

Brr... so you have (had) a problem of vibration or a tore CV boot? ;-) I guess, vibration was gone with changing of tires, and now you are to replace CV.

Was you vibration also at low speeds and acceleration dependent?

[ericem]

My front left CV has a broken boot, and it really makes the car drive like ************, it makes acceleration VERY hard(i think its seizing when i stop) i mean its super rough on accel, its like VVVVVCRACK then it smooths out(when i say crack i mean the dash board cracks, v's represent engine reving) must be very bad the CV, i think im going with OEM this time around, im done with aftermarket, they just don't last as long, even the boot quality sucks.

[crazyhorse001]

You also said you feel like it's coming from the middle of the car - that even more points toward it looking like a U-Joint. Trannys don't usually vibrate like that just going straight forward, but if the U-Joint is shot, the driveshaft will wobble a good deal. I can't honestly think of anything else except maybe a broken/half broken motor mount that would cause a vibration unless it was unbalanced tires or something simple like that.

 

+1 tho I don't believe an unbalanced tire would vibrate @ 20ish MPH. An out of round tire may cause a "thump". My bet would be a driveline part, driveshaft, cv, maybe even a diff bushing.

[nipper]

I think it's a driveshaft U-Joint. The shaft still spins whether the FWD fuse is in or not - the rear diff spins it.

 

What he said. Its the dirveshaft U joint, or the carrier bearing, or both.

 

nipper

[pearlm30]

What is the carrier bearing? Where is it located at?

Is the U joint replaceable? Or I have to get the whole drive shaft with good U joint from junk yard? BTW, how can I tell if the U joint is good or bad?

Thanks

 

 

 

What he said. Its the dirveshaft U joint, or the carrier bearing, or both.

 

nipper

[yarikoptic]

What he said. Its the dirveshaft U joint, or the carrier bearing, or both.

Following your recommendation in other thread, late in the night I've emailed http://www.driveshaftshop.com/ asking about my propeller shaft and very next morning I got a reply

yes this could be the drive shaft, one of the u-joints might be siezed in one direction. remove the shaft and check all 3 joints to make sure they

more correclty

So it seems I am doomed to check propeller shaft... hopefully the bolts on exhaust are not too rusty so I will be able to take it off. Also I am surprised that service manual doesn't say that I would need to change any gasket on the exhaust flangers if I take it apart...

[nipper]

You either get a used driveshaft, or take yours to a driveshaft shop where they will rebuild it. As per subaru, they are not servicable (but anything can be fixed with the proper tools).

 

The carrier bearing is in the center of the car under the floor, where the two driveshafts meet.

 

nipper

[yarikoptic]

Changed right CV today - vibration is still there and now (not due to CV changed but just due to evolution of the problem) I think that I can feel the same vibration (it feels in the stearing wheel and I think gas pedal) on higher speeds (>50mph) whenever I accelerate or put load on the car (going uphill).

 

During inspection of the driveshaft and found few possible participants of the vibration I feel:

 

1. center bearing. Service manual says

CENTER BEARING FREE PLAY

...

4) While holding propeller shaft near center bear-

ing with your hand, move it up and down, and left

and right to check for any abnormal bearing free

play.

but I don't see anywhere what is normal free play in this case since there is a rubber "housing" for the bearing (if I got it right) which is there to absorb vibration (should there be any). I found it quite loose imho - I could move propeller shaft any way for a centimeter or so without any heavy resistance -- I would guess it could have been harder. So, how hard (resistant) it should be?

 

2. U-joint and that shaft insert/knob on transmission side.

IMHO (I don't know how hard those should be either) transmission was also easy to move on its "mounts" - I have tried to push/pull up-down u-joint at the transmission side and there was some free play but I could not really assess if it is whole transmission going up/down or there is also some considerable free play on propeller shaft u-joint part.

 

Those weak aborbers (either AT mounts or central bearing one) would go along with my story:

they are harder when cold I guess, that is why I don't feel it while car is cold

and also it points more to AT mounts, since then even in FWD mode vibration is the same -- then it might pass to propeller shaft and get not properly aborbed by the central bearing rubber housing

 

I guess, the easiest to finally diagnose the problem, would be to go to some shop so they raise the vehicle and start to spin at 20 mph and apply some load (brakes) to see what parts start to vibrate enough to sense it in the body, and then look for a "bad cow"

[pearlm30]

Follow up on my case. I went to the junk yard to get the prop driveshaft which is out off a 97 Legecy outback. Look at the U joints, they are better than mine(95 outback) but not much better.

Got home and installed the 97 shaft and relized that the center bearing mount was different:mad: so I couldnt get the heat shield back on. Also the shaft did not look center in the guide near the rear diff.

Anyway, how can I tell my u joints are bad??? The 97 are better, but not by much. Wonder that will be enough to cause vibration???

Thanks

[nipper]

From a trucker site

SHAKE AND INSPECT. Firmly shake each end of a driveshaft, trying to move it vertically and horizontally. There should be no slack. Carefully check for loose, damaged or missing parts. Also look for signs of cup movement within the retaining hardware. Nearly all these situations would require U-joint replacement.

[pearlm30]

Can I drive the car without the prop driveshaft for troubleshooting purposes? Will the ATF dump out of the tailhousing?

Thanks again

 

 

 

From a trucker site

SHAKE AND INSPECT. Firmly shake each end of a driveshaft, trying to move it vertically and horizontally. There should be no slack. Carefully check for loose, damaged or missing parts. Also look for signs of cup movement within the retaining hardware. Nearly all these situations would require U-joint replacement.

[pearlm30]

I brought brand new axles from NAPA autoparts hoping to cure my vibration problem from 25 to 30 mph. But they made it worst. Then I thought it could be the driveshaft(prop shaft), brought a used one, still not good. Decided to just bite the bullet and get rebuild axles from CV axle.com.

I compared the both axles and NAPA is about 1 inch shorter:mad: . I think that why NAPA axles vibrate. It could be the wrong application, who knows.

So I now have cv axle.com axles in the car now, 95% of the vibration is gone:headbang: . Will get a wheel aligment & balance done tomorrow.

Lesson learned. Hope this will help someone.

[yarikoptic]

Congratulations!

I compared the both axles and NAPA is about 1 inch shorter:mad: . I think that why NAPA axles vibrate.

Do you remember by any chance what part is actually longer? Was it longer simply due to 'deeper' sitting due to excessive removal of air from within the boots? I just wonder. In my case: vibration got not as prominent but seems to be present at strong acceleration at any speed. I tried to get one day to the propellershaft, but due to rusty bolts connecting middle pipe and rear catalytic, I decided first to get a fresh gasket + 2 bolts and then simply cut old ones in half... but I put more and more doubt that it is a driveshaft -- the fact that vibration is the same with FWD mode (when no torque applied) and that it is only at acceleration (when problematic part is experiencing the load) - it is imho in frontal part but since I changed 1 CV axleand vibration wasn't gone and replaced another one with the one I removed first, unless both of them are bad, problem shouldn't have persisted... so I just don't know what to do and I am driving it as is until the problem becomes prominent and obvious.

[pearlm30]

I took some pictures just so everyone will see what I am talking about. I am trying to see if I can attach it here.

 

 

 

Congratulations! Do you remember by any chance what part is actually longer? Was it longer simply due to 'deeper' sitting due to excessive removal of air from within the boots? I just wonder. In my case: vibration got not as prominent but seems to be present at strong acceleration at any speed. I tried to get one day to the propellershaft, but due to rusty bolts connecting middle pipe and rear catalytic, I decided first to get a fresh gasket + 2 bolts and then simply cut old ones in half... but I put more and more doubt that it is a driveshaft -- the fact that vibration is the same with FWD mode (when no torque applied) and that it is only at acceleration (when problematic part is experiencing the load) - it is imho in frontal part but since I changed 1 CV axleand vibration wasn't gone and replaced another one with the one I removed first, unless both of them are bad, problem shouldn't have persisted... so I just don't know what to do and I am driving it as is until the problem becomes prominent and obvious.

[Manarius]

An inch short!? Are you sure you were getting the right ones....

[Kilroy]

I ordered a passenger side halfshaft for my '90 Legacy about 2 months ago from Bumper to Bumper. There were 2 shafts and they looked damned near identical, but there were grooves around the middle of each shaft that were different that would allow you to tell the difference between them.

[92svxman]

It seem that everyone is saying the same thing, CV, Axle, or Bearings, but on the other hand Vibration would not be the same as vibration on the out side of the bearing. Check to see if the rotor on the vibrating corner is cracking down the "Fins" show signs of cracking. If you take off the wheel and try to turn the rotor, if you meet a fin or two cracked it will get harder to turn.

Good luck with it anyway.

Michael

[yarikoptic]

Check to see if the rotor on the vibrating corner is cracking down the "Fins" show signs of cracking. If you take off the wheel and try to turn the rotor, if you meet a fin or two cracked it will get harder to turn.

Wouldn't it be prominent then not only during acceleration (which is the problem reported in the thread) -- I would expect that vibration to be present while cruising as well.