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Old 01-12-2019, 07:39 PM   #1
PVNRT
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Default Do aftermarket axles sound like rod knock when you get one that vibrates?

Hello hello, just replaced both front axles on my 2004 wrx wagon with aftermarket ones. Took it for a test drive and hear a new sound around 4k rpm, its a fixed mechanical type sound goes away when engine is not under load at any RPM. Sounds like a rattle.

I hope nobody minds me making this thread here, this place moves so slowly nowadays its good to get some conversation going.

This is the first time I have heard this sound since I have owned the car. I have heard rod knock before and it sounds similar, is it possible to only make noise at certain rpms under load or is rod knock pretty consistent at all RPMs?

I have tactrix cable and will try to do some logs tomorrow, problem is my OBD port is all loose and very hard to log anything just trying to get some info before then.

Does the ecu throw CEL when it sees detonation? Even if it isn't detonation, and it's just driveline noise, I am worried ecu will think it is and pull timing.

This sound is new since axles went in today.
I know I need to make some logs and check knock count but just trying to get some info before then.


Thanks for any help it is much appreciated.
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Old 01-12-2019, 08:06 PM   #2
PVNRT
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Forgot to add, it only makes the sound under load, revving in neutral doesn't recreate the sound. I also fixed a large exhaust leak today, so the sound might have been masked before.
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Old 01-12-2019, 08:30 PM   #3
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Is it road speed dependent, or only engine speed dependent? Do certain gears sound worse that others?
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Old 01-12-2019, 08:35 PM   #4
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I just realized something, when I finally dropped the car (not all the way on ground just enough so tires have a bit of load) I only torqued the axle nuts, lug nuts are only a little more than hand tight.

My stupid monkey brain told me I need to torque something when I drop the car, torqued the axle nuts correctly but forgot to torque lug nuts, they are on a little more than hand tight.

Hopefully this is the problem, will report back tomorrow with results in case it helps somebody in the future. I am getting drunk now, long day.

Sometimes you gotta put things in writing to go through all the steps you took, thanks for letting my stream of conciousness on your forum!
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Old 01-12-2019, 08:47 PM   #5
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Quote:
Originally Posted by Blktrax View Post
Is it road speed dependent, or only engine speed dependent? Do certain gears sound worse that others?
Agreed, same road speed but a different gear (thus RPM) is the sound frequency the same?
Yes......trans output, wheel, axle issue.
No......engine or trans input issue.

Yes, loose lugnuts would be similar in the test to axle noise since they are rotating (really hopefully......) at the same rate.
So, when sober, "check your nuts".......

Report back.
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Old 01-12-2019, 08:56 PM   #6
PVNRT
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Quote:
Originally Posted by Blktrax View Post
Is it road speed dependent, or only engine speed dependent? Do certain gears sound worse that others?
Appreciate the reply, it is only over 4k RPMs, only with more than half throttle, but it happens in all gears not dependent on vehicle speed. I need to torque lug nuts tommorow and test again.

It still might be loose tolerances on new axles, I feel like chinesium axles only vibrate with load on them. We will see what happens tomorrow.

I am making 350 whp on a stock internal ej20 but have a really good tune, I think, tuner said zero knock count even at this power level. I know I am in spun bearing territory but that is caused by oil starvation, not knock, correct? I did install killer b oil pickup before it started making this kind of power.
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Old 01-12-2019, 08:56 PM   #7
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Duplicate reply, deleted so sorry.

Last edited by PVNRT; 01-12-2019 at 09:02 PM.
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Old 01-13-2019, 01:44 PM   #8
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Well its definitely not loose lug nuts or detonation or new axle sound. Popped the hood and I can hear the same rattle sound at idle, its pretty quiet though. When I rev it in neutral it goes away completely. Wouldn't rod knock be constant? The sound kind of comes and goes at idle but stops when revved.

I can duplicate the sound every time under load between 3k and 4k rpm then it goes away. Happens in all gears.

Are there degrees of rod knock? Am I in the early stages of bearing failure or do they let go all at once?

The sound seems to be coming from the throttle body area, but it could be a bearing failing on an accessory drive maybe. The car drives great and hauls ass in this 20 degree air.

I will drain oil tomorrow and look for metal. I am just gonna keep driving it if there is no metal I guess. I figure if it is rod knock it can't be repaired anyways so I might as well blow it up. I will also remove heatshields tomorrow and go for a drive. This sound is new since I replaced the axles yesterday but it happens at idle so I dont think they are to blame. My heatshields are pretty haggard but I just cant see them making a bearing type of noise but it would make sense that they only resonate at certain RPMs.

My engine mounts and trans mounts are pretty beat too, the engine moves more than it should....can that cause bad sounds like this even at idle?

Last edited by PVNRT; 01-13-2019 at 02:23 PM.
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Old 01-13-2019, 06:01 PM   #9
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Rattle was the damn boost gauge! Noticed rattle was on drivers side, checked foot well for any loose trim etc. Noticed boost gauge needle kinda bouncy. Took her for a drive and held gauge next to my ear, sure enough at 10 psi the whole gauge rattles, definitely the source.

I also changed oil after I cut open old filter to look for metal and the underhood noise is much quieter now. Maybe lifter tick?

There were tiny traces of metal like two or three tiny tiny pieces in the oil, but it might have been contaminated from cutting filter open. I also haven't changed the filter since new turbo went in it might have been from break in?

Either way I am gonna call it good for now.

Thanks for any replies.

BTW boost gauge is mechanical autometer brand. I think I will change it to an AEM digital gauge as I don't like the idea of having vacuum line in the car anyway.
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Old 01-13-2019, 07:02 PM   #10
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The AEM X-gauges are awesome, I installed Boost, A/F and, oil pressure about 6 mos ago, best gauge investment I've ever made.

If you do oil pressure be sure to order a Killer B oil pressure sensor bung for the oil pump. The sensor is NPT vs OE Metric and you'll be waiting a week for one, when you forget.

https://www.aemelectronics.com/produ...auges/x-series
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Old 01-14-2019, 04:09 PM   #11
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i have an AEM stepper motor gauge and it doesn't work super great. you have to let it fully boot up before turning the engine over or else it doesn't read right. the digital one might be better though.
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Old 01-15-2019, 10:47 AM   #12
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Thanks everybody...what a weird ass problem to have I know but that boost gauge rattle sounded too much like detonation and or rod knock, freaked me out.

Hopefully somebody 10 years from now will see this thread and it will help.
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Old 01-15-2019, 02:37 PM   #13
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my mechanical gauge bounces as well at certain RPM and boost. im running it off the port that goes to the purge valve. i think i need to move it to the main plenum volume.
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Old 01-15-2019, 04:32 PM   #14
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Quote:
Originally Posted by CarmelValleyWRX View Post
my mechanical gauge bounces as well at certain RPM and boost. im running it off the port that goes to the purge valve. i think i need to move it to the main plenum volume.
It needs to be connected to the boost recirc (blow off valve) vacuum line.
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Old 01-15-2019, 05:15 PM   #15
Charlie-III
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Quote:
Originally Posted by PVNRT View Post
Thanks everybody...what a weird ass problem to have I know but that boost gauge rattle sounded too much like detonation and or rod knock, freaked me out.

Hopefully somebody 10 years from now will see this thread and it will help.
Yes, hopefully someone searches, finds this thread, you closed it out (thank you very much, I HATE deadend threads.....) and,maybe it helps others.

As an aside, sorry if some of us asked "random questions" but that is part of diagnosis. We start with possibly thousands of issues, questions can drop that to hundreds or less. More info and questions can narrow it down to a few......hopefully.

Thanks again for closing this out.
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Old 01-15-2019, 06:43 PM   #16
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Quote:
Originally Posted by Blktrax View Post
It needs to be connected to the boost recirc (blow off valve) vacuum line.
it certainly can be connected there. but it doesn't HAVE to be connected to the BOV hose. i already have a 1/8npt hoe in my manifold for my sending unit of the AEM boost gauge. i just need to swap it out to a brass fitting for my 1/8" hose to go onto.
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Old 01-15-2019, 08:59 PM   #17
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Quote:
Originally Posted by CarmelValleyWRX View Post
It certainly can be connected there. but it doesn't HAVE to be connected to the BOV hose. I already have a 1/8npt hoe in my manifold for my sending unit of the AEM boost gauge. I just need to swap it out to a brass fitting for my 1/8" hose to go onto.
You have a hoe in your manifold?!?! Sounds like a short hoe, midget?

Nevermind.......
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Old 01-15-2019, 09:21 PM   #18
CarmelValleyWRX
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its also a tapered hoe. you can also thread in adapters to attach flexible hoes.
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Old 01-16-2019, 10:14 AM   #19
PVNRT
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Quote:
Originally Posted by CarmelValleyWRX View Post
my mechanical gauge bounces as well at certain RPM and boost. im running it off the port that goes to the purge valve. i think i need to move it to the main plenum volume.
Yeah mine is sourced there too...I actually have an overkill 3 catch can setup, one standalone for PCV and one for each head. I have 2 PCV valves and I think that rattle sound under throttlebody I heard is one of them fast cycling making a click sound. One of them is on intake manifold to prevent pressurizing the cans. I was expecting far more blowby at this power level but the cans only have a couple small drops of oil/condensation. I probably should simplify it.
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Old 01-16-2019, 10:17 AM   #20
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Quote:
Originally Posted by Charlie-III View Post
You have a hoe in your manifold?!?! Sounds like a short hoe, midget?

Nevermind.......
Maybe the hoe has a bottle of methanol and she is trained to spray when she hears ping sounds?
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Old 01-16-2019, 11:18 AM   #21
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Quote:
Originally Posted by PVNRT View Post
Maybe the hoe has a bottle of methanol and she is trained to spray when she hears ping sounds?
Quote:
Originally Posted by PVNRT View Post
Maybe the hoe has a bottle of methanol and she is trained to spray when she hears ping sounds?
Now that sounds like my kind of hoe! Hell I'll take 2.

As far as your pcv, didn't you use an 02 WRX pcv valve? Unless your car is going from vacuum to boost as fast as you hear "cycling" then it's not the pcv.
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Old 01-16-2019, 03:47 PM   #22
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my meth hoe is in my TMIC
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Old 01-16-2019, 06:32 PM   #23
Charlie-III
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Quote:
Originally Posted by CarmelValleyWRX View Post
its also a tapered hoe. you can also thread in adapters to attach flexible hoes.
Quote:
Originally Posted by PVNRT View Post
Maybe the hoe has a bottle of methanol and she is trained to spray when she hears ping sounds?
Quote:
Originally Posted by Crispy 1 View Post
Now that sounds like my kind of hoe! Hell I'll take 2.

As far as your pcv, didn't you use an 02 WRX pcv valve? Unless your car is going from vacuum to boost as fast as you hear "cycling" then it's not the pcv.
Quote:
Originally Posted by CarmelValleyWRX View Post
my meth hoe is in my TMIC
Welllll....since chatting about hoes.......

Ahhhhh.....nope, tech section, should've kept it clean, sorry to everyone for thread derail.....

Back sorta ontrack, lots of small ports on a Subaru engine are British pipe tapered threads, quite a few US based pipe fittings are a US based thread. While really close, not really close enough.
This usually means getting the proper threaded sensor, or a couple different adaptors. I went through this when trying to "T" off the front stock oil pressure switch to add in a US type oil pressure sending unit.
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