Tootie Pang

iTrader: (2)

SO I'm refreshing the original post to clean-up what I know to stoke more thoughts from the think tank here.

Symptoms:

1. What: Open tin soup can can with three or four 1/4" ball bearings swirling and shaking the can at the bottom back and forth (like shaking a dice cup)
2. Where: Loudest by the front driver side valve cover just behind the alternator. Seems significantly loud near the front of the other valve cover too but not as loud. I can also hear it clearly from both wheel wells, above the tire. It starts each time I roll to a stop and leave it in D but then it stops fairly quickly.
3. When: Does not occur when cold, only once warmed up. Starts making noise idling in Park or Neutral. Can last for 10-20 seconds then stops. Can go longer or shorter. Somewhat random. Stops if I shift into R or D at idle. Was worse six weeks ago when it started. Less today but still very noticeable.

I have attached an actual MP3 recording of my sound. It really kicks in midway through the video.

I also sounds a lot like this:

What I am pretty sure it is NOT:

1. It is not an accessory (belt removed)
2. It is not the cat (sound is not near it at all and rubber mallet fails to rattle cat)
3. It is not the flexplate/torque converter (it is not a ticking and is not always there)
4. It is not a loose line or bracket on the engine.

What I am suspicious of:

1. Pushrod rattle or broken valve springs (but this seems unlikely according to similar threads)
2. Harmonic damper (haven't really put my hands on it but seems tight when I push on it)
3. Transmission I don't know what could be making a the noise in there and why it would loudest up by the front valve covers but it seems tied to the selector position. Maybe an internal check valve or something. I will check the brackets and connections under there.
4. Loose torque converter bolt. Seems that it may be light-loading related. P and N and approaching a stop. Also cold trans fluid probably a bit different acting than hot trans fluid in the torque converter in rattle suppression. I need to get under there and double check.

Any further ponderings appreciated.

GeneralDisorder

iTrader: (1)

For some reason I can't open the file.

Have you checked your torque converter bolts? Make sure the flexplate isn't cracked too while you are in there.

GD

Tootie Pang

iTrader: (2)

Thanks but it isn't making any noise from that area. It's loudest top of engine passenger side near AC compressor.

RBob

iTrader: (1)

Pull the serpentine belt off and see if it still makes noise. Just don't run it for more then a minute.

RBob.

NoEmissions84TA

iTrader: (1)

You can narrow it down with a piece of vacuum tubing.
Stick one end in your ear, and use the other like a stethoscope.
This works the best for noises "in the air", not transmitting through metal.
For those, you use a regular engine stethoscope.

Tootie Pang

iTrader: (2)

I will try the belt removal tomorrow. I did use the stethoscope method and couldn't really home in on the sound.

Tootie Pang

iTrader: (2)

What a week. Updated my original post.

Tootie Pang

iTrader: (2)

LATEST: I removed the serpentine belt. The sound was still there.

It is not the accessories
It is not loose lines

It is related to trans selector position P and N and then R and D. When I put it into P or N from Drive or Reverse, the sound appears. Back to D or R, RPMs drop a little, sound goes away. Like an open tin can with some ball bearings rolling around in it. Something to do with the idle RPM and/or transmission position.

I had flushed my trans with Mobil 1 ATF and it works fine. It has worked fine for a while now.

When I flushed it, I cut one of the cooling lines for the flush. Thinking I was blowing with a little air pressure back into the return line (to clear the cooler) , I was actually blowing back into the pump for a short while. That being said, I finished the flush and everything has been fine since then so I do not suspect I messed anything up. Fluid is at proper level.

I did install a vette servo a while ago as well.

Is it possible that it is my trans filter? Maybe it has somehow come loose? I bought a AC Delco filter setup with the metal filter housing. Looked good quality. Got it seated way up in there correctly I think. Maybe it slipped down?

RBob

iTrader: (1)

As GeneralDisorder posted, it may be a cracked flexplate. Happens all of the time. Need to get under the car and remove the inspection cover. Then the three torque converter bolts.

Push convertor back toward the rear of the car. Is the flex plate solid or can it be rocked?

If the flex plate is OK then start the engine and check for the noise. Gone? Then either the converter or the trans is broken.

RBob.

Tootie Pang

iTrader: (2)

Ok thanks, I will delve in there. Appreciate the procedure details!

Tootie Pang

iTrader: (2)

I have been spending a lot of time with YouTube videos and digging up even more threads on noises on these cars.
Without inspecting the flexplate, I am almost certain it is not the issue. From the videos, it's a pretty regular ticking sound. Mine is a tin can with four or five ball bearings rolling around that comes once the car warms up.

I am also pretty sure it isn't the cat. The sound isn't coming from anywhere near it.

Tootie Pang

iTrader: (2)

TOTALLY refreshed the original post. Cleaned up- lean and mean with the latest info and ready and worthy of more thoughts.

RedLeader289

iTrader: (2)

This may be a dumb suggestion but have you tried grabbing everything under the hood and giving it a good shake?

Justing thinking through everything that is bolted down under the hood and if for some reason something is just SLIGHTLY loosened and the heat from the engine at operating temp is enough to loosen enough to rattle something.

makes sense that the sound would change or go away at lower RPMS because there's not as much vibration there vs at the higher idle in park or neutral.

Have you taken the valve covers off?

Lurbie

iTrader: (3)

My guesses would have been a belt tensioner or the flexplate. Seeing as you've eliminated the belt and confident it's not the flexplate, I'd ask about engine or transmission mounts and only because you mentioned shifting from N/P into D/R aggravates it. RedLeader has a good thought too about removing valve covers. I had a friend with a 327 in a Chevelle mushroom one of his valve stems and it made the oddest noises and only at certain times.

Tootie Pang

iTrader: (2)

Yes and I'm hoping not to do it again. I fixed a leak but I suppose I could.

I've grabbed everything I can find and it seems I can home in on the sound quite acutely up by the front valve covers but nothing seems to be there. I suppose I should yank a cover and poke around.

Tootie Pang

iTrader: (2)

Yeah, I changed all the mounts a few months ago. They look good.

redneckjoe

if you have headers, try tightening the bolts at the head. sometimes they work loose and will give a ticking sound.

Tootie Pang

iTrader: (2)

Thanks, no headers. yet.

ASE doc

Rattling sound is likely loose converter bolts. That explains why it goes away when you put a load on it. The sound will transmit through the motor and can sound like it's coming from the front. Blowing back into the trans through the cooler line not something I would do. Depending on which line you blew into, you either pushed air through the lube circuit, no big deal really, or you pushed air back through the converter and converter clutch control circuit. Shouldn't have hurt anything. The filter can't fall out. It lays against the pan normally. The little hardish rubber seal that comes with the filter can leak though and cause the pump to suck air. I replace this seal with three viton o-rings.

Tootie Pang

iTrader: (2)

Thanks. I will look but the need to warm the engine for five minutes before the sound kicks in clues me that it is not a bolt.

ASE doc

After you cut the cooler lines, did you put everything back in place securely? There is a bracket towards the front of the oil pan that the lines snap into. Are the cooler lines rattling?

TylerSteez

iTrader: (3)

Pull a valve cover and check out the rockers and springs

Tootie Pang

iTrader: (2)

I am pretty sure they are not but I do not recall securing the lines down there. I will check. Thanks!

Tootie Pang

iTrader: (2)

It was the timing chain and gears. They were original and very slack. Idle caused the cam to "resonate" within the slack chain limits relative to the crank gear causing the noise and unusual idle. New set quieted everything up and engine runs noticeably better.

joeld

Glad you got it fixed.
Curious about one thing, with the cam gear being original was it nylon coated or solid steel?

Joel

GeneralDisorder

iTrader: (1)

My 86 LB9 had the factory nylon tooth cam sprocket. Sloppy but unbroken at 150k when I swapped in a roller chain.

GD

joeld

Thanks for the reply. This is what I suspected, just wasn't sure. I've had a lot of dealings with those nylon coated gears years ago. From my experience at about 100K it starts getting close to replacement time.

Joel

Tootie Pang

iTrader: (2)

That's what I was expecting. Funny thing is mine didn't appear to have had nylon on them. Chain was just really loose.