Roaring noise under load (1 Viewer)

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Here's another noise thread: I've been getting a sorta roaring noise only under load, it's not a rumble, rattle, grinding, skraping, or high pitched whine. It's more like a moan or mild roar that gets louder directly proportional to road speed and only under load, it goes away as soon as I take my foot off the gas pedal. It starts out almost immediately as I accelerate away from a stop light for example and builds in tempo until around 30-40 mph, then seems to go away and comes back sounding a bit higher pitched at 50+ and just keeps getting louder the faster I go. It's not present in neutral at any road speed or when standing still and revving the engine, only under load and moving. My front driveshaft is out and the center diff is locked but the roaring noise was present before I did that and hasn't changed (I was also getting a vibration around 50mph so took out the DS to replace the U-joints). From reading other threads it sounds like it may be a bearing noise, question is which one, rear pinion maybe??
 
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Put the front DS back in and remove the rear; see if the noise disappears.
 
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CJF; thanks, that's my plan just can't get to it for a week or so. The slight under-load vibration at ~50mph did go away when I removed the front DS, those U-joints didn't look or feel loose, just a bit stiff in one direction. The front DS had yellow paint marks on it so those U-joints are probably OEM replacements. The rear driveshaft however doesn't look like it's ever been out.
 
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Sounds more like an obstructed exhaust or maybe an hole in the intake hose if up front. Gear and bearing noises aren't engine load sensitive.
 
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Really. I interpret load sensitive as being dependent on the amount of throttle rather than being going from drive to coast. Going down hill at 60 MPH is very different than going on the flats or up hill at 60 MPH in terms of the amount of throttle required. Noises that change when you go from drive coast are often gear related but they generally don't go away completely. There is a big difference in the amount of exhaust gas flow as you open the throttle.
 
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Do you have a sound clip?

I'm having a similar noise and I'm thinking wheel bearings or trunion bearings. My front axle is in desperate need of axle service. I'm waiting on CruiserOutfitters to get another shipment of parts in because they are all out right now. I added moly to the knuckles and drain/refilled the diff and not much metal came out just some fuzzy flakes but nothing big, but a whole lot of muck came out. I did a second drain/refill after driving for awhile and no more metal fuzz but some more muck. From what I saw, I don't think it is my diff. This is why I'm leaning towards wheel bearings.
 
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Roaring under load? Need more details on "load."

Things I have experienced:
Whistling of throttle body under throttle. Defenitely not a roar except for in my triple carbed 914/6.
Fast tempo growl working into roar. Failure of a rear wheel bearing and subsiquent damage to the axle. Driving on one side of the crown on the fwy will make the sound worse on the effected side.
Slower tempo growl that is felt as much as heard. U-joint failing. Neutral throttle and coasting eases up on the noise and feel. Engine braking and throttle causes more noise and feel.

Thats all I got...
 
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It's present under normal acceleration on a level road and normal acceleration up a hill, but not present say if in cruise at 70mph and going down a hill, but comes back as soon as the engine is under load going up a rise, same road, same road speed with cruise control on. It's also present under any combination of gear, 2nd, D, OD, just harder to hear due to normal engine noise, not related to engine rpm, but definitely related to road speed; the faster I go (constant acceleration not pedal to the floor), the louder it gets. Only thing I've noticed is that both the right front and right rear hubs feel somewhat warmer than the left side hubs; hard to gauge the temp difference just by feel, but maybe the front right is 10-15 degrees hotter than the left and maybe hotter than say a year ago before I serviced the front axle with new wheel bearings. So maybe I got those wheel bearings too tight?? But on the other hand, the right front hub always seemed a bit hotter than the left. The rear axle hasn't been worked on. Also, haven't noticed any difference in the noise being on a crowned road or level, and there is no associated vibration.
 
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Bad wheel bearings make a low rumbling noise with the same periodicity as the wheel and drive/coase or the load on the engine would not matter; just the wheel speed.
Pinion bearings and U joints make a higher pitched whirring noise that is about 4x the wheel speed. The noise would typically change as you go back and forth from drive and coast, but they would also be speed related and not completely go away.

If you can hold your hand on the hub, I wouldn't worry about the temp.

Try sticking your head out of the window and listening while someone else is driving or tape a hose next to the wheels, muffler and other things and listen through the other end while someone else is driving.
 
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The noise does not seem as "fast" as the wheel speed, no real rotating component, just a continuous moan or mild roar as long as the drivetrain is under load. I'm pretty sure that the rear U-joints are the originals and didn't notice any change in the noise last time I greased those. I'll have more info once I pull the rear driveshaft in a week or so. Only other thing going on is some pulsating when I brake (but no movement or pulling of the steering wheel while braking). I think that is due to my totally worn out rear brake pads, I plan to replace those tomorrow.
 

ppc

M Go Blue
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That sounds like the viscious fan clutch is failing. The fan should spin freely until it gets hot and then lock up to suck the air through the radiator. It sounds like your fan is engaged all the time.
 
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The noise gets louder with road speed not engine speed and no noise at all if revving the engine while parked or while coasting in neutral. The fan clutch spins maybe too freely when warm.
 
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Still driving it with the front driveshaft out, still have the roar. I drained the rear 3rd member, no chunks of metal and the 75W-90 Mobil 1 gear oil still looked almost new, replaced it with WallyWorld 80W-90-140 and the noise became a bit muffled. Then added two tubes of LubroMoly gear oil additive for grins, the noise got slightly less or changed in pitch after a few days of running it, but not by much. Those two "tests" IMO helped confirm the noise was coming from the 3rd. I ran the history by a differential expert who said the noise was likely from worn pinion bearings causing loss of their preload which then results in the ring gear and pinion not meshing as they should causing the noise. He said it might possibly be the carrier bearings worn which also would also cause a ring and pinion mismatch, but being that they are so beefy he said it's more likely worn pinion bearings. Either way the 3rd needs to be rebuilt or replaced.
 
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I like the way it handles without the front driveshaft, no snow to worry about, I'm lazy.
 
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I am finding a lot of different opinions on the cause of this whine, but no one has seemed to fix it, or at least posted what the problem was. I am looking at purchasing a 93 fj80 with the same problem. 150,000 miles front and rear lockers and a nice rust free under side. The previous owner was told by his mechanic that it was pinion noise and won't leave you stranded.

The whine starts at 40mph gets a little softer at 50 and stays the same from there on. Let off the gas and the noise goes away immediately!

Any help is appriciated.
 

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