Something knocking under the floor
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Joined: Mar 2009
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From: Killarny MB
Something knocking under the floor
For example, at part throttle 4th gear, 25 mph, it feels like something is lightly knocking on the floor of the Vette at about 4 times a second. It's not loud, but I can feel it through the gas pedal, and maybe a bit from my left foot on the floor. The car is still smooth on the highway, no vibration, no noise, just at part throttle when I am in the city, I can fell a rhythmic tapping in the floor/gas pedal. Any suggestions?
Thanks! 2000 MN6 Coupe.
Thanks! 2000 MN6 Coupe.
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Joined: Mar 2009
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From: Killarny MB
Heck ya! Go skip shift....actually it is deactivated, but I shift directly into 4th from first when the light on the dash goes on just because it saves fuel and I am usually not in a hurry to go anywhere...(edit) Just looked in the owner's manual...must have read it wrong last year as it shows 4th at 40mph (2-29)... The funny thing is that the light on the dash that recommended shifting from 1st to 4th turns on when going between 15-19 mph (as stated in the manual 2-30)...weird. I always went by the light and figured 25 mph was just dandy for the car....hmmm seem like it says two different things.
The range of speed that the knocking happens is actually 25-30mph, but always at part throttle when just maintaining speed. It does not happen on the highway.
I haven't seen what rpm the engine is at in 5th at 25mph, but I am not a fan of lugging the motor. Part throttle to maintain speed, not too big of an issue, flooring in high gear at that low of an rpm is not really something I would like to do. The higher the gear I am in, the higher the rpm has to be before I feel comfortable going full throttle on the engine.
The range of speed that the knocking happens is actually 25-30mph, but always at part throttle when just maintaining speed. It does not happen on the highway.
I haven't seen what rpm the engine is at in 5th at 25mph, but I am not a fan of lugging the motor. Part throttle to maintain speed, not too big of an issue, flooring in high gear at that low of an rpm is not really something I would like to do. The higher the gear I am in, the higher the rpm has to be before I feel comfortable going full throttle on the engine.
Last edited by ChromeC5; Jun 22, 2009 at 01:41 PM.
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Burning Brakes
Joined: Apr 2009
Posts: 1,163
Likes: 4
From: Concord California
Yea, me too, I had a knocking and what sounded like screaming and yelling, I found out it was a 2005 Mustang I ran over at the stop sign...I thought it was a Pinto. Just joking guys, my Sgt. has a Mustang and is trying to always compare spec. with my vette, we run each other down all the time. He trys to tell me his car is a muscle car, I tell him the Vette is the True American Sports Car, Mustang is a family sedan with vette dreams of becoming a two seater one day..... He don't like me no more.. He makes me do all of the reports when we patrol.. But I still smile because we know the truth... Vettes are the best...
Instructor
Joined: Jun 2008
Posts: 203
Likes: 0
From: Camp Hill PA
Do you have an aftermarket exhaust? The Pypes kit I bought was bent wrong from the factory and used to bounce off my rear sway bar making a knocking that drove me crazy. I finally pulled it off and re-welded the over the axle pipes correctly to fix it.
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Joined: Mar 2009
Posts: 605
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From: Killarny MB
ahh, crap, I didn't want to bring this up, but my friend has a 98 automatic and in third at 30mph, his tack reads just over 1000 rpm and in drive, it is around 900. At 25 mph, in third it is about 1000 rpm and in drive it is cruising at 800rpm. What gives? Are people with automatics suppose to drive in second? If third is fine, why am I getting flack for driving in fourth with a manual(like third in an auto) when going 25mph and the engine is turning over 1100 rpm. The car doesn't seem to car, the engine is not knocking, pinging or anything. Let me stress that this is part throttle, just to maintain speed. Are manuals different that autos? I never put it to full throttle at this low of an rpm. This is a 350 ci engine (I know 346) that is by no means high strung (1 hp/ci which Chevy has been doing since the 60's) or technologically advanced when compared to what is out there. Is it that bad to cruise at this low of an rpm? Please set me straight...and not what you think is right, I would like someone that knows these cars and engines to properly inform me. Thanks!!!!!!
PS, sorry that this thread will not just go away and die. And,thanks for the input.
PS, sorry that this thread will not just go away and die. And,thanks for the input.
Last edited by ChromeC5; Jun 26, 2009 at 02:16 AM.
