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Half-Axle Replacement causes idle shudder....?


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I have a 00 OBW which just blew up the passengers cv boot. I replaced the axle with a NAPA part, and now when the tranny is in drive and my foot on the brake the engine shudders...or rattles. It is almost like there is a vacuum leak or something (I checked and found none). It runs fine at all other speeds, but makes this shudder until I take my foot on the brake. What do you think? Did I mess up something in the ABS? Subarus always idle ridiculously low...mine is 500 rpm, but before the axle replacement I never had any issues with it. Anyone have similar?

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My 97 Legacy does the same thing, if I put it in Park or Neutral, it will quit. Or if I kick the throtter up a little it will stop. I have not been able to get the answer for this problem here yet, but I think we will soon. I dont see how your problem could be related to the axle change, Have you tried putting it in Neutral and leaving your foot on the brake and seeing if it would stop?

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I know my 96 Legacy shakes in drive at idle because the half shafts are a little bit too long. It is not supposed to be a problem with the outbacks. In fact, the dealer says, to fix the shake, replace the legacy half shafts with outback half shafts. I am wondering if someone sold you the wrong part and it a tiny bit too long? That would be my first guess... to double check the part number. Other option is to instal a subaru OEM half shaft. I understand that they are not horribly expensive, but have not personally investigated this.

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I know my 96 Legacy shakes in drive at idle because the half shafts are a little bit too long. It is not supposed to be a problem with the outbacks. In fact, the dealer says, to fix the shake, replace the legacy half shafts with outback half shafts. I am wondering if someone sold you the wrong part and it a tiny bit too long? That would be my first guess... to double check the part number. Other option is to instal a subaru OEM half shaft. I understand that they are not horribly expensive, but have not personally investigated this.

 

Very interesting Midwst, I have never heard of this.

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  • 1 month later...

I figured it out, folks. The NAPA half-shafts are 1 inch too SHORT. I was told by the manager at Napa that the axles are made from subaru shafts, but this can't be true, because of the length difference and even difference in shaft thickness. Once I replaced both cheesy NAPA shafts with Subaru re-mans the shudder for the most part went away. (I must say though that the Portsmouth NH Napa was very nice and gave me a full refund for both shafts) :*) So thats it everyone...stick to Subaru parts...expensive, but it will save you a lot of frustration.

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I figured it out, folks. The NAPA half-shafts are 1 inch too SHORT. I was told by the manager at Napa that the axles are made from subaru shafts, but this can't be true, because of the length difference and even difference in shaft thickness. Once I replaced both cheesy NAPA shafts with Subaru re-mans the shudder for the most part went away. (I must say though that the Portsmouth NH Napa was very nice and gave me a full refund for both shafts) :*) So thats it everyone...stick to Subaru parts...expensive, but it will save you a lot of frustration.

 

This cant be right either. ONE INCH too short is dramatic in a car where sometning 5mm too short will self destruct. Yes i can understand the factory shafts being better (i have often said buy subaru shafts, anything else would be taking a chabce) but ONE INCH comeone is on drugs.

I can think that the shafts being too short, theyre would be no freeplay in them. No freeplay means that every little vibration from the engine is being transmitted to the chassis like having solid mototmounts.

Now that being said, i woud go to NAPA and DEMAND that that is put in writing, because that lack of slack could possibly damaged the transaxle or wheelbearings.

I would be pissed .....

 

 

nipper

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This cant be right either. ONE INCH too short is dramatic in a car where sometning 5mm too short will self destruct. Yes i can understand the factory shafts being better (i have often said buy subaru shafts, anything else would be taking a chabce) but ONE INCH comeone is on drugs.

I can think that the shafts being too short, theyre would be no freeplay in them. No freeplay means that every little vibration from the engine is being transmitted to the chassis like having solid mototmounts.

Now that being said, i woud go to NAPA and DEMAND that that is put in writing, because that lack of slack could possibly damaged the transaxle or wheelbearings.

I would be pissed .....

 

 

nipper

 

Well, I didn't take a photo, but i'm pretty sure they were about an inch too short...maybe the outer spindle was longer? Either way, one of them did blow up on me, which was the final straw for me to go get my money back. Strangely, my tranny fluid also went low (after a recent fill) about a quart. Maybe the vibration shook it out! Oh well. It's a used car. Stay away from aftermarket parts.

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thanx for reminding me to listen!

 

(though I think he's not too keen on subes)

Your right according to him we are a cult. I think I agree with him Subaru owners are a different breed. I am lucky I get to listen to Click and Clack, and Ed. each Saturday being I am in my car working.

 

Now on the topic of the axles I got mine rebuild from Litha Subaru and I still have the shudder when my car is at idle and in gear. Whats up with that?

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that is what is called getting the wrong part. You have to never trust anybody on parts and always double check that they are identical. I have even gotten the wrong part from Subaru on a couple of occasions. You have a better chance at the dealer, but some of these things are so close but different. On the Forester rear drums I checked them and they looked identical. They were in a box with the right part number. When you bolted up the wheel the wheels froze because the slot for the backing plate was a few thousanths out. Turned out to be for some model of imprezza.

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First we are going to assume all the motor mounts are in good shape.

While the car is in drive, parking brake on, someone in the car with thier foot on the brake.

Shutting down one cylinder at a time to see if there is any change in the idle condition of the engine. If you hit a cylinder that does not change the rounghness to a great degree, it may be an ignition/fuel issue on the one cylinder (plug or dirty injector). The one that has an issue will change the least.

 

nipper

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First we are going to assume all the motor mounts are in good shape.

While the car is in drive, parking brake on, someone in the car with thier foot on the brake.

Shutting down one cylinder at a time to see if there is any change in the idle condition of the engine. If you hit a cylinder that does not change the rounghness to a great degree, it may be an ignition/fuel issue on the one cylinder (plug or dirty injector). The one that has an issue will change the least.

 

nipper

Yes I did this about two months back, when I unpluged the # 3 injector it quit working altogether, I had to get a new E.C.U. to get it to work again, but now all four are working fine, but the shudder is still there. I have no ideal why the E.C.U. went out at the same time I was unpluging the injectors but it did. However I have not done a good check on the transmission mount, that I will check.

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thats really odd ... ECU shouldnt care as all it does is send a siganl to the coil or ignitor.

 

 

 

nipper

My nephew is a shop manager at a large dealership and he told me it most likely was on the verge of giving trouble and my action helped it along. I dont know if this is correct but it was better than anything I could come up with.

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