Humming noise on 4H on lower speeds up to ~40

Hi all,
It has been a while since I used my 4x4. So I don’t know if this always been the case or my ocd is getting worse as I am getting older. I m hearing like a humming noise on 4H on lower speeds up to 40ish maybe. It will stay the same even when I put the car in neutral while rolling at low speed.

 

Can’t say for sure what you are hearing but it is more than likely just the forward driveline engagement below you resonating through the cab. Your front driveshaft is now spinning and bringing on a “new” vibration into the cab.

 

There is going to be some noise when 4X4 is engaged. Probably normal and you just haven't used it in a while and forgot about it. Even in neutral the front driveshaft and axle are turning, just not getting power. But then again you could have a problem. Hard to diagnose on a keyboard.

FYI, I hope you aren't driving around on pavement in 4X4. Occasionally, and for short distances, and only in a straight line you should be OK. But it isn't intended to be used at highway speeds on hard surfaces with good traction. I can't think of any place where I need to be in 4X4 where I'd be driving over 20 mph.

 

The front driveshaft doesn't spin in 2wd, only the front spider gears. The additional components that spin when you make the shift are the front ring gear, transfer case front flange and the front driveshaft. My guess is likely culprit (assuming it's not a normal hum), is a worn u-joint on the front driveshaft.

 

OP when is the last time you greased u joints on front drive shaft?

 

FYI, I hope you aren't driving around on pavement in 4X4. Occasionally, and for short distances, and only in a straight line you should be OK. But it isn't intended to be used at highway speeds on hard surfaces with good traction. I can't think of any place where I need to be in 4X4 where I'd be driving over 20 mph.[/QUOTE]

Usually on snow icy roads. The manual mentions up to 60 on 4H. I almost never go that fast on 4 high.

 

2 years ago. I was planing to do it this past summer and totally forgot.

 

Stock height, like no lift or anything?

 

Yes, the only thing non stock is the 17 inch wheels out of 4Runner.
It sounds like the engine fan when you first turn on the truck in the morning and you have to listen carefully to hear it. Or feel it I guess

 

60 is max speed to drive in 4H? I doubt that. I've driven faster. Highway speed limit is 65mph or greater depending on location.
I don't see why it would have a limit

Do you mean maximum speed to turn it on while moving?

There are probably vehicles out there with 4x4 turned on due to weather going above 60 rather than following semi's in the slow lane with their hazards on

 

manual states up to 60mph TO ENGAGE 4hi.

There is zero issue going 60+ in a straight line on dry pavement (assuming same tire size and tire wear) in 4hi.

 

I don’t have the manual at the moment but as far as I can remember you can engage 4H safely below 60mph and recommended not to exceed that speed. You should use 4H on wet slippery surfaces and yea you can take turns. 4L is a different story.

 

Usually on snow icy roads. The manual mentions up to 60 on 4H. I almost never go that fast on 4 high.[/QUOTE]

Don’t worry about MarshallR. He has a long and documented history of being afraid to use 4WD on his 4x4.

 

Well, as suggested grease them universal joints, inspect them. I like doing my own maintenance like transfercase and differential fluid changes so if I seen something suspect then I know there may be an issue. This is how I discovered it may be time to do the bushing on my wife's 2nd gen. The magnet on the plug had much more fuzz on it than expected. (Hers is lifted =increased driveline/front axle cv joint stress)
My guess is just additional normal driveline noise, which you going to have especially if snow/ice pack roads. There just going to be more noise.

 

OP I have this same annoyance and thats what it is cus Ive relubed my manual hubs, taken them apart, both cv axles are fine, changed front diff oil (oil was good), greased all the driveline, ujoints are fine. I have came to rhe conclusion after 3 years that its just normal sound cus it doesnt get used daily, but 3 years later nothing has broke.

 

Usually on snow icy roads. The manual mentions up to 60 on 4H. I almost never go that fast on 4 high.[/QUOTE]
I do it all the time, just did it a week ago Sunday. The road between St Cloud and home was snow-covered and packed like ice, with blowing snow on top of it. Was able to manage a speed of 55/60 mph. You learn to stay away or slow down for the shiny spots.

 

Don’t you have to engage it at least once per month to keep it in good working order/prevent the actuator from failing

Rally drivers start out sawing a bit on the steering wheel
to feel out the road surface to know how much available traction there is

 

2 years since greasing u joints?! Bruh, go grease your front two u joints ASAP (and the three on rear driveshaft while you are at it) and pray the needle bearings havent disintegrated into powder yet. Should grease them every oil change in future as preventative.