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I've got a metallic noise which sounds like a dry bearing. I have no idea exactly where it's coming from but i'll try to explain the conditions in which i can hear it. Basically it can be heard in between gears at high rpm (above say 4500ish), and while slowing down in gear. The noise starts off higher pitched and winds down over the space of about a second while in between gears, or winds down with the rpm while slowing in gear (so for example if decelerating from 6000rpm i'll hear it till the noise fades away at about 4500rpm). I can't hear it at all while accelerating. Its alot louder when the passenger window is open, so i'm guessing it's coming from that side somewhere. I showed a mechanic and he said its the blow off valve (trust me, it isn't), and i've never heard it on any other car. It might be my imagination but i'm pretty sure it's worse on hot days. Sometimes it's really noticeable and sometimes I can't hear it at all. The only thing I can think of (which is a stab in the dark and probably wrong) is the transfer case, which whines quite bad at 100kph but otherwise seems fine. Has anyone got any ideas?

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1990 C83A 4WD 4G63T powered hatch - [PSIBRG]
1992 JZX91 2JZ powered Toyota Mark II

Vacuum/boost leak possibly. Have you tried a boost leak test?

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go fast- break stuff- repair- repeat

Hmm, it's not really an air sort of sound, more metallic. I don't know if you've ever seen/heard a crusty old skateboard wheel bearing, when you spin it it makes a dry kinda noise. That's what it sounds like (closest comparison I could come up with ) It doesn't seem to affect how the car drives, and has actually been doing it to some extent for as long as I can remember (although it seems to slooowly be getting worse). It's just something that i've kinda gotten used to and never thought much of, but now it's bugging me.

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1990 C83A 4WD 4G63T powered hatch - [PSIBRG]
1992 JZX91 2JZ powered Toyota Mark II

I'd check the fluid in the tranny and tcase -- from the drain plugs. See what you find in there.

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'18 X5
'19 M5 Comp
'07 997 Turbo, 1144WHP/1001WTQ
'17 Fiesta ST

Throw out bearing?

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1993 single turbo supra
2000 Lexus sc300
2016 ram 1500

Check out the carrier bearings for the driveshaft. I recently had to replace both them on my Galant because they were almost 100% torn through. They were so sloppy from being so torn the driveshaft had lots of room to wiggle and vibrate. It definitely made the noise a lot worse on deceleration.

Yeah I think it's drivetrain related. The closest thing to the passenger side window which is driveline related would be the transfer case I guess (don't forget i'm RHD), the noise isn't as loud with the passenger window up and driver window down.
I'll give this a look. The gearbox oil is about a year old, and transfer case oil is about 2 years old. I've only done 4000km in the last 2 years because the car has been off the road a few times, but i'm wanting to try a different oil in the gearbox to see if I can get it to shift better anyway. Might do it this week and see how it goes.
I've always thought when a throw out bearing goes bad, the noise it makes goes away when you push the clutch pedal in? With my problem it doesn't seem to matter whether the clutch is engaged or not. The clutch is about 2 years/4000km old.
Yup I know this noise. Used to make the whole car vibrate, definitely different to what i've got now though. I replaced the driveshaft carrier bearings about 3 years ago, they're still fine.

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1990 C83A 4WD 4G63T powered hatch - [PSIBRG]
1992 JZX91 2JZ powered Toyota Mark II

have you check over the car as far as wheel bearings and stuff? maybe it's in the brakes like a dust shield? input shaft bearing on the transmission? water pump? change your fluids lol. Maybe it's a timing component? does it do it under a load or just at light throttle?

Yup wheel bearings are reasonably new, about a year old. Things like that are checked over during our 6 monthly safety checks. It doesn't do it under load at all... or not that i've noticed anyway. If i'm decelerating and I can hear the noise, it goes away as soon as I apply load. I might go test that to be sure. Water pump was done in Feb, as well as timing belt, tensioner/idlers, balance shaft removal etc etc etc. I'll change the fluids this week!

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1990 C83A 4WD 4G63T powered hatch - [PSIBRG]
1992 JZX91 2JZ powered Toyota Mark II

Yea sounds like it's in the transmission or the t-case.

Or you can ride it till it dies, then you'll find out what it is....j/k

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4g61t.org
4g61t.com

Haha, that's pretty much how we roll here in NZ (and in all honesty, if a fluid change doesn't help, that's probably what i'm gonna do )
I had a better listen today, and it seems it does make the noise on acceleration, it's just generally drowned out by the sound of exhaust/turbo spool.

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1990 C83A 4WD 4G63T powered hatch - [PSIBRG]
1992 JZX91 2JZ powered Toyota Mark II

Hey i had simmilar sounds now and also before..Before the sound was my trannsmission , the throwout bearing went bad and had the same kinda sound like your talking about. Turned out we took off clutch and preasure plate and saw the throwout bearings were missing and were crunching around in there. We replaced it and clutch and everything seemed better and good except now my clutch doesnt have alot of play it just engages the last little part at the bottom. But now months later ive got another crunching sound wich sounds like is coming from eighther the alternator or ac compressor. So im going to cut my ac belt once i find out if that will effect my drivabillity or anything to see if this is the problem or not. Anyways did you ever fix your problem or figure it out? Charleyturbo....

Hey man, nah I haven't fixed/found the problem. Changed all my fluids etc, hasn't made a difference. I notice that the noise SEEMS more noticeable in 2nd gear, or it might just be easier to create the conditions in which it occurs while in 2nd, I don't know. I was trying to show a friend a few weeks ago, he couldn't hear it, so I downshifted to 2nd at about 60kph and held the throttle open just enough to maintain the current speed/rpm so the noise would be at it's loudest and most noticeable. He definitely heard it after that, but unfortunately has no idea what it could be haha. I have no air con, didn't think of the alternator, that could be something to look into.

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1990 C83A 4WD 4G63T powered hatch - [PSIBRG]
1992 JZX91 2JZ powered Toyota Mark II

Hey dude, cool glad you responded back. It seems like you have only had this problem or noise when your in second. Mine is always even at idle and then gets faster and louder as i rev. Anyways ive had similar sounds when my throwout bearing was bad recently and also when my hydrolic tensioner went out it was a waaaaaa waaaa sound. Anyways i have this crunching sound when the throwout went bad and also same or similar but different spot over bye my alternator from junk yard i just changed or the ac compressor. Anyways i need to cut my ac belt but still not possitive it wont affect anything later. I think you need to figure out where your sounds coming from. You could idle car and put it on a jack and jack stands and blocks behind tires and go under the car while it idles and listen and have a friend rev the car a bit and listen. You could even keep the car on stands and jack and put the car into gear and stand too the side and have him duplicate the rev you said you hear sounds and see if you can pinpoint sound giving you the best idea where its coming from. Also you could video tape this and sounds and put on here for us to help you. Ive never put a video but doesnt seem too hard. That would probably get a answer fast, and if it's vital for your car like a tentioner or a water pump or something then that would help you alot to save your car for the future...charleyturbo.