Sound On Deceleration HELP WANTED
Thread Starter
Teching In
Joined: Feb 2008
Posts: 15
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From: Palo Alto, CA
Sound On Deceleration HELP WANTED My question for you guys is regarding a weird sound when I let of the gas. Its like a chatter/clapping/tick/slapping or like a really messed up blowoff valve( I cant really explain it) when I switch gears or just release gas at a higher RPM. When just revving in neutral the sound still proceeds. The sound happens regardless of in gear or clutch engaged which to me eliminates the possibility of drive-line. Also happens when moving or at a stop. Background on the car. Just purchased from a female driver (Ouch) It has full exhaust, 4.10, intake, minor stuff. I just rebuilt my T-56 and put in an LS7 clutch pressure plate assembly including flywheel, throw-out bearing, slave-cylinder and pilot bearing. The sound was there before and after repair. My SES codes are for MAF and Generator circuit. The sound is pretty annoying and I really would like to get rid of it, so I am here asking the experts. If you guys have any advice or previous experience with this type of noise let me know please. I am a broke auto-tech student who really cant afford a mechanic. I do my own work so let me know what you guys think.
Thread Starter
Teching In
Joined: Feb 2008
Posts: 15
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From: Palo Alto, CA
It doesn't sound like an air leak. Sounds mechanical. Sounds like if your pouring out a large bag of coins. It seems like its a Spinning sound thats slowing down. Its really hard to explain. I will see if I can get a recording of it and post it as a sound clip
Thread Starter
Teching In
Joined: Feb 2008
Posts: 15
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From: Palo Alto, CA
Just rebuilt transmission. Plus it makes sound when not in gear or regardless of clutch position. That means the transmission output shaft is not spinning so the U-joint will not be spinning either so it cant be making the noise. My motor mounts are fairly new, and looked good while I was pulling the transmission less than a month ago. Can it be a pulley or some kind of bad bearing or valve? This sound will be the death of me.
TECH Enthusiast
Joined: Feb 2009
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Is your car moving when it makes the sound. If it is moving then your driveshaft will be turning cause your wheels are turning. I would say with the 4.10's it could be your rearend possibly gear backlash or maybe your pinion spacing isn't set just right...Trust my rearend was making a noise after I put new gears in it turns out that my pinion was .002 off and it led to a rebuild after less than 1000 miles so I might check that hope this helps.
Thread Starter
Teching In
Joined: Feb 2008
Posts: 15
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From: Palo Alto, CA
Thanks Big Bird appreciate the help. But unfortunately it happens when car is stopped as well and with clutch engaged, so nothing behind transmission is spinning. I think my backlash is off but there is a separate sound from that problem. This one is way more annoying. Even when at a light revving, on the deccel. it makes the noise. I am leaning toward valves out of adjustment.
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TECH Enthusiast
Joined: Feb 2009
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It may very well be your valves or bent/broke pushrod I sure hope it isn't but anything is possible if your drivetrain isn't rotating at all and the noise is still there then it has to be engine related...but could it be an exhaust leak maybe from your exhast manifolds or do you have headers it also could be your exhaust pipe vibrating or something. I would have your car running and take a long screwdriver or dowel rod and place it on your valve covers and see if it comes from there if not check each exhaust connection using same method when you find it you will know it then go from there good luck dude.
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Thread Starter
Teching In
Joined: Feb 2008
Posts: 15
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From: Palo Alto, CA
Thanks BigBird, I will check that out later today. I do have Long tubes that I will check out. Cross your fingers for me that its not a valve because that would really suck. And for the post below, its a new PCV but thanks for any help you can offer.
Thread Starter
Teching In
Joined: Feb 2008
Posts: 15
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From: Palo Alto, CA
I found paperwork from the previous owner. It says the car has after-market push-rods. Not sure why just the push-rods where changed, but do you think it could have something to do with the sound?
Teching In
Joined: Mar 2010
Posts: 14
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From: Bridgeport, TX
This is the sound it is making. This isn't my car, I have the magnaflow catback but the exact same sound.
http://www.ls1sounds.com/SLPloudmout...r_stockWS6.wav
http://www.ls1sounds.com/SLPloudmout...r_stockWS6.wav
Teching In
Joined: Mar 2010
Posts: 14
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From: Bridgeport, TX
Its only a sound clip but I wouldn't think exhaust rasp. It only does it when off the gas and it sounds like it is coming from under the car. I gutted my cats awhile back and thought that maybe something got stuck in the crushed y-pipe but haven't taken it down to look.
Well from what the majority of this thread is describing it sounds like Rasp..lol.
I saw it mentioned up there..there really is no way to get the Valves "out of adjustment" on a LS1.
If it is rasp then this has to be the longest thread on it..lol
Here's how you get rid of it..
I saw it mentioned up there..there really is no way to get the Valves "out of adjustment" on a LS1.
If it is rasp then this has to be the longest thread on it..lol
Here's how you get rid of it..
