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

[yarikoptic]

Here are the pictures from pearlm30

 

Imho -- NAPA's one has simply deeper sitted axle within the SFJ outer race so the rubber boot is not stressed at all and positioned per instructions within the grove on the axle. non-NAPA's one clearly stretched the boot -- look at the 2nd rubber boot 'circle' (sorry can't find a word to use).

Such 'longer' assembly might be benefitial and remove the noise

since it pushes axle stub inside differential... I wonder if I should let some air get into my boots while the car is lifteed and they are stretched so they behave this way....

[idosubaru]

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: . .

 

 

this is why MWE or used Subaru axles are the best bet. aftermarket axles for Subaru have bad percentages.

 

a driveshaft with vibration problems should be easy to diagnose off the car. the ones i've seen were typically seized (ujoint VERY hard to move or impossible) or they were very loose...obviously nearly busting out of the yoke. it's not hard to tell if that's what you're thinking. and...if you left the front half of the driveshaft in place and actually drove it in FWD then the vibration would either be gone or not, that would rule out two ujoints on the rear half which are the most likely to fail from what i've seen.

 

to run it in FWD, yes you would at least need the front half of the driveshaft in place to keep the fluid in. the rear section can be removed.

 

if they exhibit other signs...lumpy feel and minor wear, you won't feel vibrations. many, if not most older gen subaru's are pushing 20 years old and have quite lumpy u-joints by now, i haven't pulled any that were "like new". but they rarely have vibration or other issues.

 

on some subaru's the driveshaft is actually removable without removing the exhaust, it's not easy, but it does beat messing with exhaust bolts, studs and gaskets. remove any rubber hanger mounts and use some bars or tools to help move the exhaust as needed while dropping the shaft if it looks like you might have room to drop it out.

[yarikoptic]

unfortunately in my case swapping CVs with new ones didn't help even a bit -- I think even that vibration got felt stronger (may be it just degenerated even more -- need to drive a lot up the hills these days).

 

BTW -- just to share -- to swap a CV it was sufficient for me to take wheel off, disconnect the crossmember, take of the head off the ball joint (at the bottom) and knock ball joint "thread" from the arm, knock off the pin from the inner CV cup and that is it. I guess it should have minimal impact on alignment (if any), and no need to remove the brakes or abs or anything else. with smoking brakes, and alone it took around 2h per CV. The only beast I see is to disconnect ball joint (either at the top or at the bottom).

 

Anyways, after subi mechanic drove my car, he came to conclusion (unfortunate for me) that it is the torque converter clutch. See the follow up thread http://www.ultimatesubaru.org/forum/showthread.php?p=625899

[yarikoptic]

unfortunately in my case swapping CVs with new ones didn't help even a bit -- I think even that vibration got felt stronger (may be it just degenerated even more -- need to drive a lot up the hills these days).

Hi Everybody once again

Last time I've hidden 1 detail for some reason -- besides changing CVs I've changed differential fluid... Last weekend I changed diff fluid again to Lucas's 80W-90 gear + oil stabilizer in proportions close to 50/50. In my opinion (I can hardly be objective now) it did change things -- if last time I said that vibration got stronger -- I meant to say 'sharper'. Now, besides much lower gear noise at high speeds, I think it became less pronounced and softer. And at lower speeds I think it needs now a bit more torture to get wild. So it seems to be the proof that the reason of vibration is in the differential. I am going to look at it and

1. check that there are no wear signs on outer races of the bearings (which I think I should be able to take out whenever I take the retainer off). Also look at inner race but since I believe it is pressed on I will not be able to really closely inspect it
   
2. pull studs (axle shufts) out and see if there any marks on them
   
3. replace circlips at the other end of studs since I have them already (btw now whenever I am testing how well studs are sitted I feel two stages while pulling out from most inner position -- like at first (after 2-3mm circlips hit the gear and then they proceed a bit further (2-3mm I guess too) before really stopping. May be they got week within time

I already asked "Is central clutch on AT engaged when it is in N?" in another thread

http://www.ultimatesubaru.org/forum/showthread.php?p=637589 -- just to see if I can reset backlash if something goes wrong along the way or if I try something from the following: even if bearings do not have visible abnormalities, I guess they still can be undertightened thus allowing slight vibration/tilting of the axle shufts occur. That would be greatly amplified by CV shafts which sit tight on the axle shufts -- and that would cause the vibration I am trying to pin down. So my idea is to 'tighten' retainers on both sides by 1 notch more. That should not change the backlash since from both sides I will provide the same amount of displacement -- is that a right logic?

How many degrees should 1 front wheel have a freeplay between going forward/backward if the other wheel is locked and car is in P (so drive pinion supposed to be still too)? though this is composed by at least 2 backlashes (of bevel/gear and crown gear/drive pinion) -- but I guess it should also give idea on the health of the differential.

Thanks everyone for opinions in advance

[yarikoptic]

So my idea is to 'tighten' retainers on both sides by 1 notch more. That should not change the backlash since from both sides I will provide the same amount of displacement -- is that a right logic?

Ok - yesterday I have done that -- tightened by 1 more notch on each side. Besides that I did other maintnance (change AT filter, adding AT additives, replacing steering boots, replacing left CV with the original one which was there).

Now vibration has decreased significantly. Considering now smoother shifting AT, I would say, a person who does not know about vibration might not feel it at all (unless driving up the steep hill at 20mph for a bit). So, it seems to be differential. it is kinda bad that I've done so many things at once yesterday, but since before I've already pinned it down to differential, it seems to be it after all.

So, why does it happen? I guess either weaken bearing or deteriorated O-ring which presses the outer race of the bearing. I did not have enough time yesterday (and was hesitant on weather should I) to completely remove one of the retainers and have a look at the differential bearing. May be some time I will do that, but now problem seems to be so less sever that I think I can live with it. Though I have a question now

is it possible to press out inner race of differential bearing through the "opening" from the differential retainer?

I am asking because probably to properly heal the differential I should have changed bearings + o-rings, but from what I've read inner race seems to be pressed onto the diff assembly so I have little change to take it off (put a new one) without actually taking differential assembly out (ie taking whole AT out of the car)