Wierd intermittent growl - only when warm

[smithman]

Please listen to the attached audio. No known correlation to anything. With windows up, it sounds like it's coming from the transmission. With windows down it sounds like it's from all around. Gear does not matter - i've heard it in 3rd, 4th, 5th gears. Clutch in/out does not matter. The truck must be warm...after 15 minutes of driving minimum, and it happens more often on hot days. It does not affect vehicle performance, and does not cause any fluctuations in gauges. Last night I drove it for 45 minutes, and it happened once, for 1 second. The day before when it was hot, it was happening intermittently every minute or so. Any ideas?

Recent work that was done:
Driveshaft: new center bearing and u-joints, professionally balanced
BW1356: self-rebuilt, new oil pump
ZF-5: self-rebuilt with full mainshaft teardown, shifts great
Clutch: New LUK SMF, 12.25"
Engine: professionally rebuilt Heads
Fuel: Baby moose, rebuilt injectors

 

[snicklas]

I'm not 100% sure, but it sounds like a bearing to me..... One that is allowing something to spin, like a throw-out bearing, or something "inside" something.

My truck just made a similar sound, (It is an 03 Excursion) but one of the bearings in the unit hub started to fail. Not one of the main "wheel bearings" but the bearing that holds the stub shaft inside the hub. It only did it once, but I was able to figure out what it was by the heat in the hub....... Once I got the hub out, I could see this bearings needles were dry and starting to rust......

So I would iik at the throwout, bearing in the front of the transmission.... maybe something like that. Something not supporting a lot of weight, but needs to allow something to spin.......

 

[Wvdirtroad]

This doesn't help much but it has to be something in a rotating assembley. I agree with snicklas..kind of sounds like a clutch related issue.

 

[smithman]

Update...last night it did it alot when driving. I found I can put my ear against the shifter and feel the vibrations.
Thanks, I agree that throwout bearing is a likely candidate. I removed inspection cover and noticed some particles inside the bellhousing near the throwout bearing but it wasn't clear where they came from.
I'm going to drain the tranny over lunch and see if there's metal particles floating around as a 1st step, and eliminate that...as pulling the tranny for the throwout bearing will take me a bit longer.

 

[smithman]

Update....I hate lost threads.
Removed 1356 Transfer case after fluid showed too many metal particles for the few number of miles on it.
Decased and found lots of metal particles sitting in the bottom of the case.
Pump was absolutely destroyed (case slot OK). All 4 bolts were loose, retainer arm bent, and the front/rear of the pump had extreme levels of wear and were cocked on the shaft.

Shaft and drive gear are scored badly enough to warrant replacing. Everything else OK.