Noise/vibration at 1100 rpm

[swald]

Just returned from a 2400 mile round trip trek.
The first half spent towing an empty home made trailer and the last half had the trailer carrying a 4runner...so an extra ~7K between what was in the bed and what was towed.

About 300 miles from home on the return leg I noticed a noise coming from what sounds like the back of the engine/transmission area just right of center (passenger side). It starts at about 1100 rpm and disappears soon after. I hear it momentarily (again at 1100) on the way back down to idle. And it's there whether or not the clutch is engaged. There's no loss of power or slipping that I can detect - yet.

This is a 92 with a 7.3 and a zf5.

Any ideas on what this may be?

 

[ihc1470]

To clear things up some is the truck moving when you notice this and is still there if you push in on the clutch or out it makes no difference, or are you sitting still and have this issue?

 

[KansasIDI]

Just returned from a 2400 mile round trip trek.
The first half spent towing an empty home made trailer and the last half had the trailer carrying a 4runner...so an extra ~7K between what was in the bed and what was towed.

About 300 miles from home on the return leg I noticed a noise coming from what sounds like the back of the engine/transmission area just right of center (passenger side). It starts at about 1100 rpm and disappears soon after. I hear it momentarily (again at 1100) on the way back down to idle. And it's there whether or not the clutch is engaged. There's no loss of power or slipping that I can detect - yet.

This is a 92 with a 7.3 and a zf5.

Any ideas on what this may be?

Which flywheel do you have? Single mass or dual? The single mass do make a noise, but in my experience that usually occurs at a lower RPM in lower gears. Which gears do you hear the noise in? Does it make it in neutral?

 

[swald]

To clear things up some is the truck moving when you notice this and is still there if you push in on the clutch or out it makes no difference, or are you sitting still and have this issue?

Good thought. I haven't tried just revving the engine while not in gear.
I'll have to do that and report back.
So far, the truck has always been moving. I can confirm that I hear it when the clutch pedal is in both positions (released and depressed).

 

[swald]

Which flywheel do you have? Single mass or dual? The single mass do make a noise, but in my experience that usually occurs at a lower RPM in lower gears. Which gears do you hear the noise in? Does it make it in neutral?

Not sure but this was done less than 20K miles ago (before I had the truck):

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[Black dawg]

Make sure a/c lines are not touching any of the body, or wiper motor.

 

[swald]

Thanks @Black dawg I'll check that.

 

[swald]

I have confirmed the vibration exists at that rpm regardless of whether or not the clutch pedal is depressed or whether or not the tranny is in neutral.

 

[Nero]

Then its definitely something in the engine. Maybe blown exhaust gasket? If it happens at engine speed but not vehicle motion, Something in the engine, maybe double check the transmission bolt torque?

 

[swald]

Thanks @Nero I'll poke around those and look for something out of place.