Wierd noise after launch... help diagnose - 3000GT/Stealth International Message Center

VirginiaTechVR4 · 01-14-2008, 05:54 AM

Ok, so here is the story...

New clutch, SPEC Stage 3+, just put 750 miles on it, of which 650 were city driving... so I wanted to try a launch.. nothing crazy, just a 4K drop...

So rev up to 4k, drop the clutch, front wheels spin for a sec, just a chirp, and car takes off, and bogs... so i put the clutch in, and stop, and try again...

2nd try i ease the clutch out a little more, sort of bogs, but grabs and goes, so do a 1-2-3 shift and head home..., everything seems fine

When I get to my apartment complex and make a few stops i realized there is a grinding noise in 1st gear, def in sinc with the wheel rpm, not so much engine rpm...

I can hear it sometimes in 1st gear accel, but sometimes not... but I hear it everytime in 1st gear decel, with the accelerator in just a little or out. If engine revs are coming down, the noise is present in 1st gear. I thought i heard it once in 2nd gear, but I have not been able to get it to do it again.

The noise is best described as a whine, or metal grind with a frequency tied to wheel (driveline) rpm.

Any ideas as to what could have happened??? Car shifts/runs smooth, just this noise when i happen to be in 1st decel.

I have a gmeter in the in the car, so when it stops snowing im going to go out and do a 1-2-3 run and log power, if its under 150 I will know im in FWD and fried the VCU, though I don't think this would have happened. I also need to see if the noise goes away when I put the clutch in, I think it does, but need to verify. Could it be the clutch?

Thanks,

Tony

1viciousVR4 · 01-15-2008, 03:56 PM

mine does that also in 1st gear, no other gears, never paid attention to it, it sounds like im driving in reverse just not nearly as loud, but that kind of whine.

VirginiaTechVR4 · 01-15-2008, 04:41 PM

yea, its a similar whine, but i think on mine its more of a grind... Hopefully I will have time this weekend to do some troubleshooting and update this thread so i can figure this out...

SirLaughaloTT · 01-15-2008, 04:43 PM

Could possibly be the throw out bearing.....oooor it could be a shard of metal winding through first gear ripping up lol probably not tho.....

KORMEX · 01-17-2008, 04:49 PM

Quote:

Originally Posted by VirginiaTechVR4

Ok, so here is the story...

New clutch, SPEC Stage 3+, just put 750 miles on it, of which 650 were city driving... so I wanted to try a launch.. nothing crazy, just a 4K drop...

So rev up to 4k, drop the clutch, front wheels spin for a sec, just a chirp, and car takes off, and bogs... so i put the clutch in, and stop, and try again...

2nd try i ease the clutch out a little more, sort of bogs, but grabs and goes, so do a 1-2-3 shift and head home..., everything seems fine

When I get to my apartment complex and make a few stops i realized there is a grinding noise in 1st gear, def in sinc with the wheel rpm, not so much engine rpm...

I can hear it sometimes in 1st gear accel, but sometimes not... but I hear it everytime in 1st gear decel, with the accelerator in just a little or out. If engine revs are coming down, the noise is present in 1st gear. I thought i heard it once in 2nd gear, but I have not been able to get it to do it again.

The noise is best described as a whine, or metal grind with a frequency tied to wheel (driveline) rpm.

Any ideas as to what could have happened??? Car shifts/runs smooth, just this noise when i happen to be in 1st decel.

I have a gmeter in the in the car, so when it stops snowing im going to go out and do a 1-2-3 run and log power, if its under 150 I will know im in FWD and fried the VCU, though I don't think this would have happened. I also need to see if the noise goes away when I put the clutch in, I think it does, but need to verify. Could it be the clutch?

Thanks,

Tony

The gmeter thing doesn't make alot of sense to me , maybe i'm not following you .

BTW its almost imposible to describe a sound through text

VirginiaTechVR4 · 01-17-2008, 06:26 PM

Agreed. noise and text just dont go hand in hand... but its prob. too faint to pick up with a camera...

On the gmeter, it knows the weight of the car, and somehow it calculates acceleration (not sure how) and can display horsepower. If its in FWD I would think the car would accelerate less quickly, therefore the gmeter would pick up less horsepower (based strictly off acceleration, i know the car is still make XX HP). At least in theory this sounded like it could be a way to tell.

All in all, its just a noise... maybe I'll just drive it till it breaks, who knows... how often is anyone in 1st gear decel anyways.

Ill try a couple more things over the frigid weekend and maybe some local 3S guys can come over and listen in.

KORMEX · 01-18-2008, 05:48 AM

Having a blown VCU would make your car act like it has an "open" ctr dieeferential and not like its FWD . The gMeter has a small accelerometer to measure acceleration but it doesn't know anything about traction and other variables.

To troubleshoot your noise you need to get your car on a lift and listen from underneath

banktech78 · 06-17-2008, 08:58 AM

Did you ever determine what the issue was? Mine has that problem too from time to time and only in 1st gear....Weird.

973KGT · 06-17-2008, 09:08 AM

Personally I would never use first gear in the 6-speed to decel. It's to short and by the time your going slow enough to safely put it in 1st gear your almost at a stop anyway.

The way your launching is taking a toll on your entire drivetrain by the way. When you launch these cars or any AWD really, it is always good practice NOT to drop the clutch. You need to rev to about 5-6K then slip the clutch out until the drivetrain in loaded up. Once you get to that point you can release the clutch and go. This will also solve the "bogging" issue which is caused from you building boost in the very begining but loosing that boost through the part of first gear because the rpms drop below boost. When you slip the clutch you keep the rpms up and therefore boost.

Bret Brinkmann · 06-17-2008, 09:51 AM

Clutch noises are associated with engine speed not vehicle speed. If your VCU popped, then you would spin the front tires pretty good not just chirp them. I agree with 973KGT, your launch technique is too abusive. Dumping clutches especially above 5K rpms breaks stuff and is unnessisary for most cars. Try releaseing it "relitively" slow at first untill you can feel it start to grab, then let it out the rest of the way as fast as you can. It will take some practice, but the lower you can get your rpms on a launch the better you will be. Start off with lower rpms and work your way higher. Breaking is more embaresing than loseing. And costly. If you absolutely can not launch the car lower than 5K, then it is time for bell housing reinforcement.

As for your concern, the first question that comes to my mind, is what gear oil you are using? has the tranny been taken appart resently?

01-14-2008, 05:54 AM	#1 (permalink)
VirginiaTechVR4 DR650R-Powered; IPS-Built Join Date: Oct 2005 Location: Cincinnati, OH Drives: '95 Mariana Blue VR4 Trader Rating: (1)	Wierd noise after launch... help diagnose Ok, so here is the story... New clutch, SPEC Stage 3+, just put 750 miles on it, of which 650 were city driving... so I wanted to try a launch.. nothing crazy, just a 4K drop... So rev up to 4k, drop the clutch, front wheels spin for a sec, just a chirp, and car takes off, and bogs... so i put the clutch in, and stop, and try again... 2nd try i ease the clutch out a little more, sort of bogs, but grabs and goes, so do a 1-2-3 shift and head home..., everything seems fine When I get to my apartment complex and make a few stops i realized there is a grinding noise in 1st gear, def in sinc with the wheel rpm, not so much engine rpm... I can hear it sometimes in 1st gear accel, but sometimes not... but I hear it everytime in 1st gear decel, with the accelerator in just a little or out. If engine revs are coming down, the noise is present in 1st gear. I thought i heard it once in 2nd gear, but I have not been able to get it to do it again. The noise is best described as a whine, or metal grind with a frequency tied to wheel (driveline) rpm. Any ideas as to what could have happened??? Car shifts/runs smooth, just this noise when i happen to be in 1st decel. I have a gmeter in the in the car, so when it stops snowing im going to go out and do a 1-2-3 run and log power, if its under 150 I will know im in FWD and fried the VCU, though I don't think this would have happened. I also need to see if the noise goes away when I put the clutch in, I think it does, but need to verify. Could it be the clutch? Thanks, Tony __________________ 1995 Mariana Blue Pearl 3000GT VR-4 NG '08 - 1st Place Best 2nd Gen, 1st Place Best Exterior, 1st Place Best Interior Nov. '06 - Ride of the Month Quote from some guy: "What kind of car is this?", Me: "Mitsubishi", guy: "Brand New huh?", Me: with a big ass grin "um, its a 95." Previous Member: llushman --> 3SI Member Since Feb 2004 --> 3S Owner Since August 2002 Proud Customer of IPS Motorsports 1995 3000GT SL - Supercharged - R.I.P - Dec. 2003

01-15-2008, 03:56 PM	#2 (permalink)
1viciousVR4 Never finished Join Date: Apr 2006 Location: Toms River, NJ Drives: Nowhere Fast Trader Rating: (28)	Re: Wierd noise after launch... help diagnose mine does that also in 1st gear, no other gears, never paid attention to it, it sounds like im driving in reverse just not nearly as loud, but that kind of whine. __________________ 99 Chevy Silverado 2500 93 3000GT VR4 So far: 3sx TD05 E16g Turbo Kit, polished Greddy FMIC with IPS tdo5 extensions, AEM EMS, PTE 680cc, Poopra pump, 3sx pulley, MSD wires, NGK coppers, Maximal powdercoated valve covers, polished plenum, Tial Q bov, Hallman Pro RX MBC, Maximal solid mounts, Maximal test pipe, JIC catback, Tein s-techs, Mod-Express 8k HID, Nelson TC bracket, Fidanza flywheel, RPS Max street, Deft CF hood.

01-15-2008, 04:41 PM	#3 (permalink)
VirginiaTechVR4 DR650R-Powered; IPS-Built Join Date: Oct 2005 Location: Cincinnati, OH Drives: '95 Mariana Blue VR4 Trader Rating: (1)	Re: Wierd noise after launch... help diagnose yea, its a similar whine, but i think on mine its more of a grind... Hopefully I will have time this weekend to do some troubleshooting and update this thread so i can figure this out...

01-15-2008, 04:43 PM	#4 (permalink)
SirLaughaloTT Forum Member Join Date: Feb 2007 Location: poughkeepsie ny 1260 Trader Rating: (0)	Re: Wierd noise after launch... help diagnose Could possibly be the throw out bearing.....oooor it could be a shard of metal winding through first gear ripping up lol probably not tho..... __________________ Turbo in the blood In Loving memory of Richie Bonini It won't be long will meet again Tdo5 headers, evo III 16g's, manual boost controller, denso full pump hotwired, egr delete, soild motor mounts, 680 injects,godspeed front mount intercooler 24x12x4 with ppe piping. aeromotive Fuel pressure regulater, sx fuel filter steel braided lines, greddy ultimate,lc-1 wideband AC delete, cruise control delete..I think thats all

01-17-2008, 06:26 PM	#6 (permalink)
VirginiaTechVR4 DR650R-Powered; IPS-Built Join Date: Oct 2005 Location: Cincinnati, OH Drives: '95 Mariana Blue VR4 Trader Rating: (1)	Re: Wierd noise after launch... help diagnose Agreed. noise and text just dont go hand in hand... but its prob. too faint to pick up with a camera... On the gmeter, it knows the weight of the car, and somehow it calculates acceleration (not sure how) and can display horsepower. If its in FWD I would think the car would accelerate less quickly, therefore the gmeter would pick up less horsepower (based strictly off acceleration, i know the car is still make XX HP). At least in theory this sounded like it could be a way to tell. All in all, its just a noise... maybe I'll just drive it till it breaks, who knows... how often is anyone in 1st gear decel anyways. Ill try a couple more things over the frigid weekend and maybe some local 3S guys can come over and listen in.

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01-18-2008, 05:48 AM	#7 (permalink)
KORMEX Forum Member Join Date: Mar 2000 Location: Ontario,ca,USA Trader Rating: (11)	Re: Wierd noise after launch... help diagnose Having a blown VCU would make your car act like it has an "open" ctr dieeferential and not like its FWD . The gMeter has a small accelerometer to measure acceleration but it doesn't know anything about traction and other variables. To troubleshoot your noise you need to get your car on a lift and listen from underneath

06-17-2008, 08:58 AM	#8 (permalink)
banktech78 New User - Please be kind Join Date: Feb 2008 Location: Round Rock/Austin,TX Drives: '92 RT/TT, '95 SL Trader Rating: (0)	Re: Wierd noise after launch... help diagnose Did you ever determine what the issue was? Mine has that problem too from time to time and only in 1st gear....Weird.

06-17-2008, 09:08 AM	#9 (permalink)
973KGT Forum Member Join Date: Jul 2007 Drives: 1997 3000GT VR4 Trader Rating: (0)	Re: Wierd noise after launch... help diagnose Personally I would never use first gear in the 6-speed to decel. It's to short and by the time your going slow enough to safely put it in 1st gear your almost at a stop anyway. The way your launching is taking a toll on your entire drivetrain by the way. When you launch these cars or any AWD really, it is always good practice NOT to drop the clutch. You need to rev to about 5-6K then slip the clutch out until the drivetrain in loaded up. Once you get to that point you can release the clutch and go. This will also solve the "bogging" issue which is caused from you building boost in the very begining but loosing that boost through the part of first gear because the rpms drop below boost. When you slip the clutch you keep the rpms up and therefore boost. __________________ The 'mod bug' is like herpes - even if you get it under control, it's only a matter of time before it comes back to remind you it's still there I tend to judge people on their use of the English language

06-17-2008, 09:51 AM	#10 (permalink)
Bret Brinkmann Gear Head Join Date: Mar 2001 Location: Charlotte NC Drives: Rear wheels only... Trader Rating: (4)	Re: Wierd noise after launch... help diagnose Clutch noises are associated with engine speed not vehicle speed. If your VCU popped, then you would spin the front tires pretty good not just chirp them. I agree with 973KGT, your launch technique is too abusive. Dumping clutches especially above 5K rpms breaks stuff and is unnessisary for most cars. Try releaseing it "relitively" slow at first untill you can feel it start to grab, then let it out the rest of the way as fast as you can. It will take some practice, but the lower you can get your rpms on a launch the better you will be. Start off with lower rpms and work your way higher. Breaking is more embaresing than loseing. And costly. If you absolutely can not launch the car lower than 5K, then it is time for bell housing reinforcement. As for your concern, the first question that comes to my mind, is what gear oil you are using? has the tranny been taken appart resently? __________________ When asked what the best thing to come out of Italy is, most Italians will tell you Ferrari.... But if you ask me it was Super Mario Brothers. 250 RWHP If you want the exploded views of both 5 and 6 speeds or pics e-mail me at SavagTiger@AOL.com. 94 VR-4 Panama Green Tan Interior RPS II, gutted cats, flipped BPV, 3SX control arms, 3SX shift bushings, Red Line, Auto-Meter. Rebuilt TC, transaxle, steering rack, heads, and turbos. 360cc's blue printened with in 1%. New short block. RWD convertion and welded rear end.