Hi everyone. Developed a noise last night. In any gear, driving with foot on the gas, no noise. As soon as i let off the gas i hear a good growl. Can almost feel it in the floor. When i push in the clutch or put it into neutral, the noise stops. Any ideas?

2004 rubicon
5 speed
4.0l

Thanks everyone

Different in 4wd vs 2wd? Sounds more like a potential for differential gear noise than trans. Did this gradually get louder and louder or happen all of the sudden?

no lift all stock?

Lifted 4 inches. I originally thought diff as well. Until i pushed in the clutch/neutral and it went away. Ive had several people tell me it is probably the throwout bearing, clutch grabs high so it needs to be replaced anyways. Just trying to see of any one here has had a similar problem

Although you may need a clutch job, the throw out bearing only spins if there is pressure on the clutch pedal, so a bad to bearing is not likely. I would start by checking u-joints and cv joint. You may want to pull the axle end of the front drive shaft, tape up the u-joint cups, tie it up out of the way and go for a ride. If the noise disappears, it's an issue in the front ds. If not, pull the rear ds completely and go for a ride in 4 high.

Throw out bearing would be noisy when the clutch is pressed down. It is not under load when the clutch pedal is up and driving or in neutral.
If the sound goes away under throttle, or when the clutch pedal is pressed the 'coast' side of your gears are likely the cause of the noise.
Because you hear it in all gears I don't suspect the transmission ( normally that would be noisy in 1st, 2nd and 3rd gear. But gone in 4th and 5th. as the input shaft bearing is the typical culprit).
I think you're looking at diff. Try putting it in 4wheel drive (don't do this on pavement obviously) and see if when coasting the sound is less apparent (load split between both front and rear diff) It should get quieter if its the rear diff (taking all the strain in 2wd) If this makes sense.

Also check for any "side to side" and "in and out" play on your pinion (with DL removed). A bad pinion bearing will make that growl grinding sound.

Thanks for the good responses everyone. Since I posted this on friday, I havent heard a single strange noise. The sound I heard is gone. I am watching my front diff closely tho. Rear was just rebuilt recently. Ive got new ujoints all around. The only vigrin territory are trans(which does whine in 1st, 2nd, 3rd, more of a gear whine than a bearing howl), transfer case, and front diff.

I think Ive narrowed it down to gears up front. If i spin a tire fast while its jacked up it makes the same noise, just slower/quieter.

Have you tried disconnecting the front drive shaft from the pinion? Could be centering ball or u joint on front driveshaft.

It could be your throwout bearing. I say this because I had a noise that would occasionally occur, and didn't matter whether foot was on clutch, gas, or neither. Would do it for a bit while driving, then next time I started it up, the noise would be gone for a few months, do it again and be gone again next time I started it up. I thought it "might" be the TO bearing but figured it would get worse and more persistent if it was. Never could pin it down -- until a couple weeks ago, with no warning, clutch went to floor and couldn't get it into gear at all. Turns out TO bearing had pretty much fallen to pieces--everything else looked ok. Getting entire clutch assembly replaced right now -- figured I might as well while they are in there.