rattle rattle thunder clatter boom boom boom...

[05crewcab]

Strange thing started happening this week...

When my truck is moving and under load, (accelerating, driving up a hill, etc.) I have this rather loud clattering noise coming from someplace in or near the engine bay. It doesn't happen if I don't have my foot in it, and won't make the noise in Park.

I crawled under the truck tonight and checked everywhere for things touching the drivetrain...exhaust hangers, trans cooler lines, kickdown cable, speedo cable, PS lines, loose brackets, starter, etc. I also checked and greased my u-joints and the carrier bearing is in good shape.

Anyone have any ideas on what to check next? The motor sounds fine when revving in Park, and doesn't make this noise at idle or over 3000 RPM... I'm stumped.

[oldschool18]

does it seem to be missing when its doing this

[05crewcab]

I don't think it is missing/stumbling, etc. the power seems normal as near as i can tell.

[steves1967]

Detonation?? What's the engine timing?

[oldschool18]

mine was doing that then it started to miss and it was a bad plug wire, and mine only did it when it was under a load....going up hill.....accelerating quick

[05crewcab]

No idea what the timing is unfortunately...I haven't touched it since I bought it two years ago.

[05crewcab]

Originally Posted by oldschool18

mine was doing that then it started to miss and it was a bad plug wire, and mine only did it when it was under a load....going up hill.....accelerating quick

That's intersting. I'll have to check the plug wires...I didn't think such a loud noise could be a bad wire. it literally sounds like something is banging off the fan.

[hotrod100]

Check for a broken flex plate. I just got done replacing one in a Suburban that was doing the exact same thing. It ended up having two small cracks around the mounting bolts and wouldn't make any noise until you got on it a bit then it would start snapping and popping. We really heard it when we were towing the boat! Unfortunately you may not be able to visually find the cracks until you pull the trans. I even used my borescope and couldn't see it. On a more positive note though, the parts are fairly cheap.

[MikeyMan]

Maybe a bad motor mount? Inspect the fan shroud to see if the fan has rubbed it.

[Nova_Cobra64]

I've experienced something similar in the past, turned out to be loose torque converter bolts.
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[jocko]

is it getting louder as time goes by? (hate to suggest a rod bearing...) Hopefully not.

[Lee H]

U Joints?

[RexDodge]

Originally Posted by MikeyMan

Maybe a bad motor mount? Inspect the fan shroud to see if the fan has rubbed it.

I think Mikey got it! I'd have to vote motor mounts too...

[sanford66]

Originally Posted by hotrod100

Check for a broken flex plate. I just got done replacing one in a Suburban that was doing the exact same thing. It ended up having two small cracks around the mounting bolts and wouldn't make any noise until you got on it a bit then it would start snapping and popping. We really heard it when we were towing the boat! Unfortunately you may not be able to visually find the cracks until you pull the trans. I even used my borescope and couldn't see it. On a more positive note though, the parts are fairly cheap.

X2 on this theory. When the flexplate is cracked it will make a lot of clatter and racket sometimes. Also the sounds can change with the RPM. Joseph

[Critter]

I'm in the broken flex plate crowd, had them do weird things before. Also the torque converter bolts as mentioned, either way still need to look at the same area of the truck.

[05crewcab]

Flexplate might make sense. I took the fan shroud out to make sure and it still does it. Here is a quick video I took this afternoon. (sorry for the poor camera skills)

http://youtu.be/n4gX-dlJxVk?t=1m

[FLEET72]

Tried to look but all I got was:

This video is unavailable
This video is private.
Sorry about that.

[05crewcab]

whoops... here is the correct link:

Old Truck Clatterin down the road. - YouTube

[old Chevy guy]

Sounds rough,whats the oil preasure look like when it does that? Is the presure good overall? Seems like mostly under a load,is that right? Does it get worse as it gets hotter?

[05crewcab]

Overall oil pressure seems fine, and I have only driven it far enough to get to operating temp, but i would say it does get more consistent as the truck warms.

[jsbgump]

You have a broken flywheel or loose torque converter bolts. I have had this problem serveral times on my 68 and that was the problem. You probably can't tell the flexplate is broken until it's unbolted

[oldschool18]

Thats nothing like I thought you were talking about, i would go with the above and say flywheel-flex plate..........had a 76 camaro sounded kinda like that, missing one fly wheel bolt and the other two were loose

[FLEET72]

I concur, the flexplate is where I would start looking.

[05crewcab]

I got real curious tonight after hearing a couple more yeh's for flywheel so I crawled under took a look. From the surface the flywheel looks pristine, so i checked the torque converter bolts. two were really tight, and the third i could turn maybe a 1/2 turn. I'll take the truck out tomorrow and see if this was the smoking gun. If not, I guess the flywheel comes out...

[shawno72]

I got the same sound right now and I believe it to be the flex plate to.
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