Knock sound in gear?
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Knock sound in gear? Hello,
I have a 98 z28 with 81k miles a4 stock. Pretty much out of the blue I have a some what intermittent metallic knocking type noise ONLY in drive or reverse when warm.. Engine sounds perfect in park or netural. The car runs great outside of this issue. I have had the car since 20k miles and have been meticulous with maintenance.
I've checked for loose torque converter bolts, they were tight. Changed starter thinking it could be weak on retraction since it was original. Changed oil and filter, and trans fluid is clear and like new, changed filter 15k mi ago and did dump and fills. Oil pressure seems in acceptable range and is quick to rise with throttle, Oil psi cold start 60~ warm idle 40~ hot idle in gear 20~ hot idle park 35~ 55mph 40~ full throttle 60~psi Car isn't raced or abused, rare wot..
Is it possibly the flexplate? I was reading, the 98s generally don't encounter cracked flexplates?
Any help is so appreciated
I have a 98 z28 with 81k miles a4 stock. Pretty much out of the blue I have a some what intermittent metallic knocking type noise ONLY in drive or reverse when warm.. Engine sounds perfect in park or netural. The car runs great outside of this issue. I have had the car since 20k miles and have been meticulous with maintenance.
I've checked for loose torque converter bolts, they were tight. Changed starter thinking it could be weak on retraction since it was original. Changed oil and filter, and trans fluid is clear and like new, changed filter 15k mi ago and did dump and fills. Oil pressure seems in acceptable range and is quick to rise with throttle, Oil psi cold start 60~ warm idle 40~ hot idle in gear 20~ hot idle park 35~ 55mph 40~ full throttle 60~psi Car isn't raced or abused, rare wot..
Is it possibly the flexplate? I was reading, the 98s generally don't encounter cracked flexplates?
Any help is so appreciated
Last edited by Camaro223; Dec 5, 2022 at 08:45 AM.
Joined: Nov 2001
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From: Schiller Park, ILL Member: #317
Cracked flexplate is much less likely with an early car like yours vs. the weaker later design but, of course, it's still not impossible.
The other thing to consider is the fact that your idle speed is lower in drive/reverse than in park/neutral, so if the noise is originating in/on the engine it might be brought on by load or lower rpms (such as in gear). You could test this by power braking the car to bring the rpms up just a bit while the car is stationary in gear, see if the noise is still present.
Or am I misunderstanding? Is the noise present above idle speed, like when cruising? But then goes away when you shift to neutral (while still moving)?
Also, what gears does the car have - 2.73 (GU2) or 3.23 (GU5)? I ask because, if it came with 3.23s then it would have the aluminum driveshaft and these were known to sometimes have issues with "tinking" (or metallic clicking type noise), but usually only at the moment of being shifted into gear and/or while the car was automatically upshifting while driving (not really just sitting there at idle in gear). My '99 had this problem horribly, and my '00 had it to a smaller degree. The steel driveshaft cars don't have this condition.
The other thing to consider is the fact that your idle speed is lower in drive/reverse than in park/neutral, so if the noise is originating in/on the engine it might be brought on by load or lower rpms (such as in gear). You could test this by power braking the car to bring the rpms up just a bit while the car is stationary in gear, see if the noise is still present.
Or am I misunderstanding? Is the noise present above idle speed, like when cruising? But then goes away when you shift to neutral (while still moving)?
Also, what gears does the car have - 2.73 (GU2) or 3.23 (GU5)? I ask because, if it came with 3.23s then it would have the aluminum driveshaft and these were known to sometimes have issues with "tinking" (or metallic clicking type noise), but usually only at the moment of being shifted into gear and/or while the car was automatically upshifting while driving (not really just sitting there at idle in gear). My '99 had this problem horribly, and my '00 had it to a smaller degree. The steel driveshaft cars don't have this condition.
Thread Starter
Teching In
Joined: Jul 2018
Posts: 49
Likes: 1
Cracked flexplate is much less likely with an early car like yours vs. the weaker later design but, of course, it's still not impossible.
The other thing to consider is the fact that your idle speed is lower in drive/reverse than in park/neutral, so if the noise is originating in/on the engine it might be brought on by load or lower rpms (such as in gear). You could test this by power braking the car to bring the rpms up just a bit while the car is stationary in gear, see if the noise is still present.
Or am I misunderstanding? Is the noise present above idle speed, like when cruising? But then goes away when you shift to neutral (while still moving)?
Also, what gears does the car have - 2.73 (GU2) or 3.23 (GU5)? I ask because, if it came with 3.23s then it would have the aluminum driveshaft and these were known to sometimes have issues with "tinking" (or metallic clicking type noise), but usually only at the moment of being shifted into gear and/or while the car was automatically upshifting while driving (not really just sitting there at idle in gear). My '99 had this problem horribly, and my '00 had it to a smaller degree. The steel driveshaft cars don't have this condition.
The other thing to consider is the fact that your idle speed is lower in drive/reverse than in park/neutral, so if the noise is originating in/on the engine it might be brought on by load or lower rpms (such as in gear). You could test this by power braking the car to bring the rpms up just a bit while the car is stationary in gear, see if the noise is still present.
Or am I misunderstanding? Is the noise present above idle speed, like when cruising? But then goes away when you shift to neutral (while still moving)?
Also, what gears does the car have - 2.73 (GU2) or 3.23 (GU5)? I ask because, if it came with 3.23s then it would have the aluminum driveshaft and these were known to sometimes have issues with "tinking" (or metallic clicking type noise), but usually only at the moment of being shifted into gear and/or while the car was automatically upshifting while driving (not really just sitting there at idle in gear). My '99 had this problem horribly, and my '00 had it to a smaller degree. The steel driveshaft cars don't have this condition.
Its a 2.73 car. I've not noticed any sounds when driving, just at quiet stop lights or a drive through in gear. Any time load/throttle is applied the sound seems to stop. I have tried to do a small power braking and it seemed to have stop the sound also.
In gear the rpm via scan tool is 680~ rpm in park/netural .. I can't recall in gear perfectly but I think its 450-550~ rpm
Last edited by Camaro223; Dec 5, 2022 at 06:55 PM.
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From: Knappa, Oregon
Are you sure of the integrity of your exhaust system? A broken exhaust can sound just fine if the break is small and held together in the same position while idleing. Take a close look at the exhaust.
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I did a quick look over of the exhaust, I couldn't see anything out of the ordinary, nothing looked to be making contact or anything. However i didnt look too in depth. The knocking can be felt in the gear shifter when its occurring.
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I have not however there is no clunking when going into gear and no middle console thud. I did replace it along with u joints as general up keep some where in the neighborhood of about 30k miles ago
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Almost a year later and 3k miles I still have this issue I've done numerous things to try and remedy the issue .. Car runs great and has zero noise unless foot is on brake in R or D. In park engine running is smooth and normal throughout rpms and during driving.
Anyone since encounter anything like this?
Anyone since encounter anything like this?
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