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Excessive Up and Down Front Axle Play


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17 replies to this topic

#1 meddler

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Posted 22 March 2008 - 05:01 PM

I posted a little while ago about a noise that appeared to be coming from the transmission area of my 1998 Legacy Outback (178,000 miles, 2.5, 5 speed). I took a peek under the car today and happened to notice that my left front half-shaft had about 3/8" play up and down - where it meets the splined shaft coming out of the transmission. It appeared like the transmission had an adjustment for this, so I removed the lock and was able to turn the adjuster in several teeth. I wasn't able to get rid of all of the play, but the noise was reduced on my test drive afterwards. Is there a special tool for making this adjustment - it was difficult to do because the teeth on the adjuster are aluminum and the only method I had of turning it was using a punch and hammer. Does anybody know what's behind the adjuster - maybe there is there a bearing or bushing I should be replacing rather than simply tightening it?

#2 tcspeer

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Posted 22 March 2008 - 06:08 PM

Your going to get a lecture for this, I got one just for thinking about doing it. I would not drive it to much until you hear some of the thoughts on it and then make up your mind. Or you can do a search on replaceing transaxle seals and get some of the thoughts that already are posted on this subject.

#3 nipper

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Posted 22 March 2008 - 06:56 PM

I would lecture him, but I am not even sure what he is talking about.

nipper

#4 meddler

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Posted 22 March 2008 - 07:03 PM

Your going to get a lecture for this, I got one just for thinking about doing it. I would not drive it to much until you hear some of the thoughts on it and then make up your mind. Or you can do a search on replaceing transaxle seals and get some of the thoughts that already are posted on this subject.


Would you care to elaborate?

#5 nipper

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Posted 22 March 2008 - 07:18 PM

Would you care to elaborate?


Would you care to elaborate?

The only thing i can think of is that you may have just done a very very bad thing.

The only thing i can think of that you may have adjusted is the baclash adjustment on the differential bearings. Not all bearings are meant to be tight, some are meant to be a little loose so when things expand as they get hot they dont bind. That is supposed to be adjusted tight, then backed off by three notches.

Any way to show us a picture of what you adjusted?


nipper

#6 meddler

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Posted 22 March 2008 - 07:20 PM

From what I've read on other threads, it looks like i did adjust the backlash adjustment. It seems like this may have been a bad move... But would three notches be enough to cause a problem?

#7 nipper

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Posted 22 March 2008 - 07:24 PM

From what I've read on other threads, it looks like i did adjust the backlash adjustment. It seems like this may have been a bad move... But would three notches be enough to cause a problem?


Oh yes, it can tear the bearings and gears right up. The differential gets hot. It does a lot of work. That three notch rule is right out of the FSM.

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#8 meddler

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Posted 22 March 2008 - 07:35 PM

I've driven 60 miles after making the adjustment without any problem. I'm hoping that because there is presumably some wear due to the car's mileage, my minor adjustment will only have compensated for that.

#9 nipper

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Posted 22 March 2008 - 07:43 PM

I've driven 60 miles after making the adjustment without any problem. I'm hoping that because there is presumably some wear due to the car's mileage, my minor adjustment will only have compensated for that.


How can you tell? It doesnt happen instantly, its a slow process. One day on a 300 mile drive (60 is nothing) youll notice a whine.

But as i always say, its your car to ruin a differnetial on. Its just been a standard practice as long as they have been making differentials, and something that subaru calls out specifically.

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#10 tcspeer

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Posted 22 March 2008 - 11:36 PM

You most likly have not hurt it yet, I would put it back where it was until you get the reseach you need to decide if you want to tighten it. Are you sure that play is not in the joints of the C.V.? Did you check it with the other side?
I took the the adj. ring off of a Subaru transmission that was out of my car and no good. It did not look like it had any control on any adj. to me, but I have seen where someone here posted the information out of the F.S.M. and it did say it had to be set right as Nipper says.

#11 GeneralDisorder

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Posted 23 March 2008 - 02:05 AM

It's not just the bearings - it's the front differential gear backlash that is set by those adjustment rings. If one side seems loose, you cannot just adjust the one side. You have to adjust both sides - they move the gears, and they set the bearing load. If you move one side, you'll cause the gears to mesh poorly - the contact patch will be reduced and this causes excessive heat, wear, and eventual failure.

You NEVER touch the backlash adjusters. If the bearings fail behind the adjusters then you need a new transmission or it needs to be rebuilt. At the very least the bearings must be replaced, and the backlash reset. The procedure requires splitting the transmission though.

GD

#12 98obster

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Posted 30 December 2009 - 09:54 PM

Better to search and revive an old thread than start a new one?

I seem to have the same problem on the front driver side axle stub. I've replace the axle twice thinking it was just a bad doj. I don't think there would be any noise if the baffle plate on the doj side wasn't there. the seal seems okay since there is no leaking. the axle stub wobble seems to dimish when I make right turns.

I'm thinking of turning clockwise (inward) just 1 notch on the retainer to see if thats "stabilizes" the axle stub somewhat. Otherwise I might later (when it gets warmer) replace the seal and bearing (can I do that on the car?).

I could always remove the baffle plate that is making the noise but then the axle and stub would be allowed to wobble in a larger radius.

the axle stub shaft doesn't pull out or anything and I wish it were just a matter of tapping on it to make it click it tighter or something.

no other tranny noises or whines. fluid is new cause I recently pulled 1.5 qts of ATF out (double lip oil seal seems fin) but I'm wondering if something might have been damaged or worn to affect backlash?

#13 Fairtax4me

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Posted 30 December 2009 - 10:49 PM

Backlash is not your issue, and adjusting it will not help.
"Backlash" refers to the amount of play in a gear set. It is the amount of space between the teeth on the ring gear and pinion gear. It has to be set at a very specific margin for proper wear, heat production/dissipation, and overall longevity of the gears.

Trying to correct the "wiggle" of the stub by adjusting the bearing retainer has no effect on the stub and will do nothing but cause damage to the differential.
There is no adjustment for the axle stub. All it does is slide into the side gear and is then held in the differential by a snap ring. If the stub is loose, you deal with it. Replacement means you have to split the case and remove the differential. More of a PITA than it's worth.


Here's an exploded view of the front diff so you can see what I'm talking about.
http://opposedforces...illustration_1/

#14 98obster

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Posted 30 December 2009 - 11:17 PM

thanks. I see the diagram, any idea what has failed or worn? I would suspect that the 4eat has a certain amount of wobble so it doesn't bind. couldn't it be just a worn out o-ring (3) or roller bearing (17) that can be replaced on the car making sure to return the retainer to the exact position? Otherwise I'm just going to remove the baffle plate and save up for a tranny swap.:-\

#15 Fairtax4me

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Posted 31 December 2009 - 11:45 AM

That O ring is only a seal for the bearing retainer. The bearing doesn't touch the axle stub so replacing that will have no effect.

The bearing is pressed onto the differential carrier as seen in this pic: http://i209.photobuc...le/DSCF0039.jpg
not very clear but its the best I could come up with right away.
The stub sticks through the differential carrier but the carrier is between the stub and the bearing.
If there were anything that could be replaced to help "cure" the problem it would be the stub itself and the shim washer behind the side gear. But even then it may not fix the problem entirely because the carrier itself will also be worn where the stub makes contact.
There is play in that stub because of the design. It may be less when the differential is brand new, but there is still play.

So I suppose if you really wanted to "fix it" or make the play as little as possible, the easiest (and probably cheapest unless you have the proper tools) way would be to buy a new transmission.

#16 uniberp

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Posted 31 December 2009 - 02:12 PM

I thought those adjusters were always really difficult to rotate, being a large diameter. If they were loose enough to turn easily, would that indicate something having come loose and out of adjustment? It seems unlikely that wear alone could cause that much movement.

#17 Fairtax4me

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Posted 31 December 2009 - 05:01 PM

If they feel "loose" its probably because the O ring seals are dried out. They should not be extremely difficult to turn though.

#18 98obster

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Posted 01 January 2010 - 05:29 PM

I removed the inner baffle plate off the axle-same noise so that wasn't the problem. didn't touch the retainer mostly because I don't want to try something without the right tool.

Anyway, I drained the gear oil (valvoline) and and refilled with Lucas, 80-90 of course. It now seems the gear chatter (that's the only thing I can think it could be at this point) has disappeared.

I don't know if I increased the viscosity a little more by removing any last remaining ATF from my last gear oil change about 2 weeks ago or if there are significant differences in gear oils. If this solves most of the issue I would think Lucas an excellent choice for high mileage 4eats.

anyone use a heavier oil than 80-90 for older diffs?




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