Jump to content
81 K20

81 K20 knocking/tapping metal noise

Recommended Posts

I have an 81 Chevy K20 and this issue is driving me nuts. The tapping/knocking noise only occurs when in gear and it is in tune with my rpm. In park/neutral i can floor it and no noise at all. Since this issue started the idle also has become rough. The noise seems to be coming from the driver side of the truck. I can try to attach a video to show sound if anyone thinks that would help. I would really appreciate any ideas!

 

Things I have tried:

 

- fixed all of my exhaust leaks

 

- checked flex plate, no visible cracks, made sure bolts were tight

 

- checked bolts on manifold covers and they were all tight as well.

Share this post


Link to post
Share on other sites

Is the idle rough in both park / neutral and in gear, or just when it's in gear?

Share this post


Link to post
Share on other sites

Depending on your answer to the above I'm guessing so far something transmission related.

Edited by ifixedit

Share this post


Link to post
Share on other sites

Idle stays rough in or out of gear. I keep hearing flex plate but my flexplate looks fine to me.

Share this post


Link to post
Share on other sites

A bad flex plate can be tough to determine without removing it as they crack very close to the bolt holes which is tough to see when the converter is in the way. It's possibly the flex plate but I'd more so suspect the torque converter itself. A bad converter will usually make a clunking or ticking sound when they are getting bad, it may also make a creeking or kind of a metal on metal scraping sound when you go from drive to reverse with your foot on the brake. Can you remove the tranny dust / inspection cover and let it idle in park while you take a look at the converter spinning from under the truck? If it's the converter it will be pretty obvious, you'll be able to hear it. A bad or vibrating converter could also cause the engine to feel like the idle is rough.

Edited by ifixedit

Share this post


Link to post
Share on other sites

Just had a friend come over this morning and he said it is pinging. How loud can pinging get? At full load the issue is LOUD. I tried adjusting timing both ways and when accelerating can hear noise still. It's def not the torque converter from what i can tell.

Share this post


Link to post
Share on other sites

Just did a compression test and found water in the 5th cylinder...bummer

Share this post


Link to post
Share on other sites

Just did a compression test and found water in the 5th cylinder...bummer

 

Ahhh, blown head gasket. That could definitely cause that type of noise. Had a slightly leaking head gasket on my 350 in my Camaro last summer after a rebuild, it was kind of a chirping metallic squeaking sound off and on and I could not for the life of me figure out what the issue was. Once I had the head (Dart, junk!) off you could see a dark spot on the block deck surface where the exhaust gases had been escaping under the gasket. Fortunately for me there was no coolant leak. I turned the Darts in and got a refund, put on a set of GM Vortecs and VIOLA! Runs like a champ!

Share this post


Link to post
Share on other sites

It's got more problems then that i'm noticin...i figure i'll just find another 350 and do a swap...or if i can find a good deal might make the swap to diesel if i can, thanks for your help on this!

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.