Who wants to debug a drive train noise?

[dubya_rx]

Jeez there's a lot of stickied posts in this forum. Anyway...

Trying to debug a noise in the drive train again.
It's a mechanical "knock knock knock" noise. Most apparent when making right turns under power. If power is not applied (coasting) the noise goes away. Left turns, no noise. I can sometimes make the noise under straight line acceleration from a standing start but engine noise usually drowns it out. Unless the road is a bit slick, and then it comes on quicker and is easier to hear.

I don't feel anything through the steering. The noise seems louder inside the car... ie rolling down the windows does not make it easier to hear.

Things that have been swapped or replaced with no difference to the noise:
Left side complete knuckle (including bearing)
Left side axle
Front control arms
Struts all around (switched summer to winter mode)
Front sway bar is off the car
Front U sub brace is off the car

I'm thinking my centre or front diff is toast. But I don't want to influence anyone's opinion.

Maybe I should make a poll and go with the popular choice.

[valheru]

Sounds like a diff, but which one?

[Cavemanrjc]

I would think if it was a center diff you would feel it in the tunnel
hows the condition of the fluid? clear or metallic bits in it?
is there any fragments on the magnetic fill and drain plugs?
you said its easier on slick road
is it accompanied by front or rear wheel spin if its with fronts and one side has better trac You will have front wheel speed differences same as turning
Where do you hear it front of the tunnel mid rear?
dose it do it under light load

did you look for a walnut on top of trans yet?
they make a nasty noise

mounts and alignment of Engine and trans good?

[dubya_rx]

I have not looked at the fluid, but that would be a good thing to do.

I don't need wheel spin as it only requires loading of the gears to make a noise. When turning if I let off the gas then the noise goes away.

I feels like its in the front of the car.

I have found a walnut on the top of a strut before... little buggers.

The engine mounts look ok, but the trans mounts might be getting old. Harder to see.

[westwind999]

My Legacy made a knock knock knock sound on Right Turns too. I replaced the RIGHT CV shaft and all is well now. (I see you only replaced the Left shaft)

[dubya_rx]

Right front axle was replaced last year.

Oil drained... looks pretty dark. Here is the drain plug, with and without all the shavings. Not looking good IMHO.

[Cavemanrjc]

Those bits dont look good.
usaly youl get black very fine meterial could be thick on plug but still fine

that looks a littel corser then the norm

Did not ask one question auto or manual trans?
if manual is it in all gears?

the bits almost look like the case hardening is starting to come off one or more gears.
I would suspect spider gear in the diff
but have all looked at closely for pitting

Its just telling you that its time for a 6spd :)

[STeveD]

Like Rob mentioned, I have only ever found fine grey powder on my transmission and diff plug magnets.

[nevermind the folowing... just re-read to see that you changed the LF already. But, that was going to be my next step]

When were the front wheel bearings done? I remember chaning out some marginal CV joints because of clicking on my front axles once things were hot, and it didn't help. Turned out to be front bearing carnage. They felt snug at first on a tire tug test, but the bearings had self-destructed internally once things were disassembled.

If you confirm this to be the cause, consider the 6gunracing kit. It saves you money in the long run. Else, at least repack the OE bearings with synthetic grease. Amsoil 2000 Racing grease, or Lucas Synthetic Wheel Bearing grease are proven choices.

[Navigator]

Walter a couple questions and then maybe I can give you an opinion.

How many KM on the tranny and diff. How many times did you change the fluids and ummm how many events lapping/solosprints/autocrosses have you done?

[dubya_rx]

Good question about which gears it happens in. It doesn't seem to be gear dependent. At least I've noticed it in 1st, 2nd, and 3rd.

240K on the transmission. Is that a lot? *wink*

Last fluid change was at 215K with Motul and Redline (I think... I'll have to check my receipts).

I've done a few lapping/solosprints on the car. *grin* No autocrosses though. Although I did load launch control into the ECU last summer. Maybe that did it.

Six speed would be nice but not sure if it's worth putting too much more money into this.

Thanks!

[AndrewR]

STI STI STI STI

[JoeT]

AndrewR wrote:
STI STI STI STI

Hey, where did you learn to swear in french? LOL

http://yelims5.free.fr/VroumVroum/VroumVroum16.gif

[Navigator]

An 02 gear box with 40+? days at the track and 240k .... ummm I think thats a miracle. Were these not the "glass" transmissions. Keep driving it till it gets worse or you blow it up, whatever comes first.

I have a 6 speed if you want to go that route, and if your looking for a rebuild can get you some good gears for it.

The one in the rally car lasted almost 270km but Nuwan drives slow
:-P ;-)

[dubya_rx]

My 240K transmission lives on!

With Dan's help we determined it to be the new axle on the passenger side I replaced last year. The outer CV joint has a lot of play. Replaced with the original 240K km driver's side axle and the noise is gone.

Looks like westwind999 wins the prize!!

[Cavemanrjc]

good to hear hope it still had waranty
Defective parts suck

[westwind999]

Thanks

Glad you found it. It's not the first time a replacement CV Shaft failed early.