Help! klunking noise at idle

[looney1316]

1990 6sp. when warm i get a klunking or knocking noise under the car,can't tell if it is engine or trans.its alittle less with clutch in and it seams to only start to do it at idle like at a light or that is just the only time i hear it.had car for less than a year runs greats.last owner had a new clutch put in i have the paper work.thanks for any help.

 

[OldCorvetteFan]

1990 6sp. when warm i get a klunking or knocking noise under the car,can't tell if it is engine or trans.its alittle less with clutch in and it seams to only start to do it at idle like at a light or that is just the only time i hear it.had car for less than a year runs greats.last owner had a new clutch put in i have the paper work.thanks for any help.

Does the noise change with RPM? What about with the clutch in or out (tranny in neutral)?

How hot is the engine (coolant and oil) when the noise starts? Does it gradually start as temperature increases, or is it more sudden as soon as the engine comes to a particular temperature?

Is there any noticeable change in engine sound? What about vibration?

Can you describe the noise? Is it a low frequency or high? A single noise, or like a double knock? The more specific here the better!

Steven

 

[looney1316]

just got back from shop noise is fly wheel we think any idea how much to replace

 

[G Winter]

You mentioned that a clutch was installed before you bought the car. Do you know if the flywheel was replaced and was it replaced with a dual mass or a standard flywheel.In the 90 if you don't have the dual mass you can get noises from the transmission. Attempt to find out if the correct clutch was installed. I purchased my new flywheel and clutch kit from
http://www.carolinaclutch.com/

Flywheel just under $700 clutch kit just under $300
shipping about $34

Be sure that whoever installs it understands what they are doing.
Glenn

 

[looney1316]

the receit shows it was resurfaced

 

[G Winter]

I had a conversation with a tech at Carolina Clutch and he didn't feel resurfacing the dual mass from a corvette was a good idea because the grindings get into the inside and it can not be disassembled to clean it out. Also he stated the there is a facing and springs inside that wear out. Based on this I installed a new flywheel in mine.

Glenn

BTW how many miles are on the car and how many of those did you put on ?

 

[looney1316]

105500miles i put on 500

 

[JohnGrawcock]

Check the easiest thing first.

Have the bolts worked loose? They should have been installed with thread lock but people forget now and then.

 

[looney1316]

hopfully i can check it out this weekend

 

[looney1316]

just had it looked at by a vett guy, he said it is the flywheel

 

[G Winter]

Is the plan of action to replace the flywheel and clutch?
I would recommend staying with the OEM setup. Unless you really hammer on it a lot .


Glenn

 

[JimBobC4]

Is the plan of action to replace the flywheel and clutch?
I would recommend staying with the OEM setup. Unless you really hammer on it a lot .


Glenn

Why ? Due to clutch slippage to spair the drivetrain ? or wear and tear on components from the added stress ?

I know my clutch will wear out eventually, and I've been scouting for alternatives.

 

[looney1316]

clutch was replaced 2 yr ago before i got the car , but seeing that i have paper work that this was i'm thinking an fool did the work because he mach. the flywheel and now it is bad again the smart thing is yo do it all again the right way don't you think

 

[G Winter]

clutch was replaced 2 yr ago before i got the car , but seeing that i have paper work that this was i'm thinking an fool did the work because he mach. the flywheel and now it is bad again the smart thing is yo do it all again the right way don't you think

Yes do it right. I considered having my flywheel refaced but after my conversation with Carolina Clutch I decided it wasn't worth the risk.Here is a link to a post I made that covers most of what they told me.
http://www.corvettevalley.com/showthread.php?t=11073&highlight=conversation

Glenn

 

[G Winter]

Why ? Due to clutch slippage to spair the drivetrain ? or wear and tear on components from the added stress ?

I know my clutch will wear out eventually, and I've been scouting for alternatives.

From my research I found that the dual mass flywheel setup's purpose is to dampen engine pulses to eliminate transmission noise at idle.
If you plan on abusing the clutch and don't mind the transmission noise then a performance type of clutch with the solid flywheel might be a better option. There have been cases where eliminated the dual mass flywheel has NOT resulted in excessive transmission noise.
For normal street use I felt staying with the dual mass was the way to go, I don't like drive line noises.

Glenn