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Unread 09-04-2013, 11:43 AM   #1
roscopcoltrane
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Would like to ID a transmission "rattle"...

Sounds like a can of marbles when accelerating. It's amplified when you've slowed down and should have down shifted from, say, 4th to 3rd as you're exiting a corner at speed. But you've left it in 4th and now you're accelerating in the wrong gear. The problem isn't restricted to this scenario though. It does only occur under slightly heavier acceleration.

Man, I'm bad at explaining things like this. I believe it to be very common though. I've heard it on many manual trans vehicles over the years and I'm simply curious as to what it is. It seems to be getting worse on the Jeep. That or I'm intently listening for it now. I'm a bit of a hypochondriac when it comes to abnormal noises. Anyway, thanks in advance!

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Unread 09-04-2013, 12:16 PM   #2
LumpyGrits
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Ign 'knock' maybe?
Try a tank of prem. gas.
LG
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Unread 09-04-2013, 01:11 PM   #3
walkerhoundvm
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^^Or your timing is off^^

Also check your exhaust integrity. A couple loose bolts connecting the manifold to the downpipe or widening cracks in the pipe and that's exactly what it'll sound like: a bunch of rocks in a tin can.
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Unread 09-04-2013, 02:11 PM   #4
roscopcoltrane
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I've burned 93 octane with no effect.

My timing isn't staying put after setting it. It's good for a week or two before getting all wonky, running on, etc. I imagine the chain is stretched out. Can you explain what I'm hearing if it is a timing issue?

Will check exhaust tonight. Replaced the entire thing a month ago so it would make sense if a bolt backed out since they were seeing action for the first time in who know how long.

Thanks for the leads!
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Unread 09-04-2013, 02:15 PM   #5
LumpyGrits
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When was the last time the 'cat' was replaced?
When was the last time you put a few drops of oil on the dizzy shaft under where the rotor sits?
Can you move the dizzy by hand after you tighten the clamp bolt??

LG
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Unread 09-04-2013, 02:29 PM   #6
roscopcoltrane
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Quote:
Originally Posted by LumpyGrits View Post
When was the last time the 'cat' was replaced?
When was the last time you put a few drops of oil on the dizzy shaft under where the rotor sits?
Can you move the dizzy by hand after you tighten the clamp bolt??

LG
I just bought her a month ago. Ran a couple thousand miles over the previous 2-3 years but it wasn't seeing much action. I put it directly into daily service upon receipt, after replacing the exhaust. It didn't have a cat on it and I put one on.

I haven't oiled the distributor shaft, but will. It won't budge after tightening.
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Unread 09-04-2013, 02:33 PM   #7
LumpyGrits
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When a 'cat' comes apart internally, it can sound like a bunch of marbles, pretty loud too. The pellets can also plug the muffler up.

LG
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Unread 09-04-2013, 02:44 PM   #8
walkerhoundvm
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Check all your exhaust bolts. It's safe insurance. I put a new mani on a couple of years ago, and a month later had that same sound going on, and it got worse. Checked my manifold to downpipe bolts, and they were loose.

Long story, but it ended up being crap gaskets made by Clifford (just one of many crap Clifford products, don't get me started). The gaskets failed, the blots were "loose," and had that marbles in a tin can sound. Replaced the gaskets, tightened the bolts, and all gone
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Unread 09-04-2013, 02:58 PM   #9
OleBlue73
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I experience that knock sound as well in my 304 in driving conditions like you explain. Mine is most notable when pulling a grade in high gear. It's more like lifter chatter or ignition knock as previously mentioned. Running 93 helps me some.
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Unread 09-04-2013, 03:34 PM   #10
Matt1981CJ7
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Quote:
Originally Posted by roscopcoltrane View Post
I've burned 93 octane with no effect.

My timing isn't staying put after setting it. It's good for a week or two before getting all wonky, running on, etc. I imagine the chain is stretched out. Can you explain what I'm hearing if it is a timing issue?

Thanks for the leads!
If it's timing related, which I'm leaning towards, it's a condition called detonation. Most likely you have too much spark advance, which causes increased cylinder pressure and unburned end gases will spontaneously ignite.

The pressure spike this creates causes the engine to resonate, as if you struck it with a hammer. It can be very destructive to rings, pistons, and can cause overheating.

I'd order up a new timing set (chain and gears), if I were you.

Matt
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Unread 09-04-2013, 07:34 PM   #11
OleBlue73
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In my case, my initial timing must be spot on because my engine starts and idles perfectly. If I have too much timing advance, how do I back it off? Original Delco remy distributor
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Unread 09-04-2013, 07:58 PM   #12
Matt1981CJ7
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Quote:
Originally Posted by OleBlue73 View Post
In my case, my initial timing must be spot on because my engine starts and idles perfectly. If I have too much timing advance, how do I back it off? Original Delco remy distributor
What is your initial timing, and how quickly does your mechanical come in, and how much?

These engines will start and idle fine with 20+ degrees of advance. In fact, that's how they run best at idle. But, if all of that advance is coming from initial, not a combo of initial and vacuum, then it will most likely rattle like a can of marbles with a load on it.

Matt
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Unread 09-04-2013, 08:43 PM   #13
OleBlue73
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Quote:
Originally Posted by Matt1981CJ7

What is your initial timing, and how quickly does your mechanical come in, and how much?

These engines will start and idle fine with 20+ degrees of advance. In fact, that's how they run best at idle. But, if all of that advance is coming from initial, not a combo of initial and vacuum, then it will most likely rattle like a can of marbles with a load on it.

Matt
Something I'll need to research. Thanks
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Unread 09-05-2013, 11:09 AM   #14
roscopcoltrane
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Ran out of time last night but I did put a wrench on the manifold bolts and I was able to give each a 1/4 turn with only two fingers. Is that normal? Don't they get torqued to 25 ft/lb? I'm not fooling with it anymore until I get my torque wrench back.

That said, the marbles-in-a-can noise seemed to be greatly reduced this morning. Hoping I'm on to something here. This place is invaluable.
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Unread 09-05-2013, 11:25 AM   #15
walkerhoundvm
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Not normal. And I'm not sure what the torque is but I tend to torque them the best I can given the space constraints.
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