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Discussion Starter #1 (Edited)
2009 Chevy Silverado, 5.3L, 94,000 on the clock. When I'm towing and the truck down shifts, I get an intermittent vibration. It almost vibrates on like a 4 count: BRRR...pause...BRRR...pause, etc. It's not an overly violent vibration, but almost like going over a rumble strip.

I was racking my brain over this, and I'm thinking it's the transmission mount. I checked the joints on the rear driveshaft and noticed I could lift the transfer case slightly while checking them. It's the only think I can thing of. Anything turning, I think would vibrate constantly.

Anyone else have an issue like this, or experience it in a Chebby?

Thanks!
 

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It’s a continuous vibration. The on and off is harmonics on a sine wave. Remember science class in high school?

Now, why, is a different story. Those trucks love killing motor mounts, so check those. The rubber deteriorates pretty rapidly, especially the dr side. Also, if it has a carrier bearing on the driveshaft, check that too. After that, go to engine imbalance like normal tune up stuff (you have 100k on it) or even intake gaskets that can let air in and cause a vibration, are a good start.

Any other drivability issues?
 

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Discussion Starter #5 (Edited)
It’s a continuous vibration. The on and off is harmonics on a sine wave. Remember science class in high school?

Now, why, is a different story. Those trucks love killing motor mounts, so check those. The rubber deteriorates pretty rapidly, especially the dr side. Also, if it has a carrier bearing on the driveshaft, check that too. After that, go to engine imbalance like normal tune up stuff (you have 100k on it) or even intake gaskets that can let air in and cause a vibration, are a good start.

Any other drivability issues?
Science class in high school? Yeah, right.

I'll check those motor mounts as well. I don't think it has a carrier bearing...I'll check to see about that as well.

Drives great. This doubles as my DD. Has newer plugs, oil changes every 3,000 miles since I bought it with 45,000 on it, can't think of much other maintenance. This is definitely only specific to higher RPM's, so I'm trying to narrow it down that way. It's also really hard to check for a fix, since I only ever get it on highway as 99% of the time my truck never sees those RPM's unless towing or passing up a hill.
 

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They had a recall for the exhaust shields rattling on some models. The fix was a weighted hose clamp. :laughing:
 

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Probably closer 9,000-9,250 with gear, two grown adults, spare tires, tools, etc. Still heavy for a half ton in WV mountains. My truck usually weighs 5,600lbs. at the scales getting gravel, before they load me.
People gross 9k with a decent sized boat behind a Ford Explorer and they don't bitch about it. :laughing:
 

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Discussion Starter #10 (Edited)
People gross 9k with a decent sized boat behind a Ford Explorer and they don't bitch about it. :laughing:
Not bitching. Got a vibration. I never said this was a HEAVY load, but given the inclines it's a decent load on a half ton, and when passing slower semis maintaining 60-65 mph with traffic puts some load on the motor.

Why even bother...thanks, Rttoys, after searching motor mounts it seems like a very common issue on these.
 

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Discussion Starter #11
I replaced both motor mounts and the transmission mount. Vibration is gone. Original estimation was wrong, the vibration started around 4,250RPMS to 5,500 RPM's. Forgot 6,000+ is in the red. Those motor mounts are a pain to replace on a 4wd, and what the fawk is up with the heat shields on those things? I tossed them. Even if it ruins the mounts faster it's a helluva lot easier replacing them without those meat grinders shoved in there.

Really kicking around the idea of replacing U-joints, just in case. Going to try and make it down to Virginia to grab an old, rust free Cherokee and tow it home.
 
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