4Hi hums? Is it normal?

Probably a dumb question but I figure it wouldn't hurt to ask since I'm new to 4Runners. I bought it used over the summer and I'm already aware they have some noisy mechanisms, so I want to be sure this might be another one!

We have been using 4Hi pretty heavily on a 300 mile trip through a blizzard, it's our first time using it this season. Lots of snowdrifts and ice. Never going over 55 with 4Hi on! But turned it off when we felt safer/went faster. It engages and disengages fine, and works great! But I notice a deep (not whiny or grinding) hum when maintaining speed, and it goes away when I let off the gas. Also goes away entirely in H2. It is loudest between 30-50 MPH, almost like an aggressive exhaust. Just wondering if that's a normal 4Hi sound on 4Runners?? At 99k miles. I haven't serviced the trans, transfer case or diffs yet, I was gonna do that after 100k

 

Could be several things including tires. Our truck driveline in 4H is quiet but does have a 2H rear diff whine when decelerating.

 

I thought maybe it was tires or the sound of ice and snow on the road, I have BFG's and they make their own noise but it's definitely not them. It stops as soon as 4Hi is turned off

 

Just an FYI, you don't need to limit your speed to 55mph when in 4H. I've gone 100+ mph over the years in most of my 4WD vehicles without an issue. As well, the owners manual only states that you should shift into 4H at max speed of 50 mph.

 

Normal, every 4Wheel drive I've had does the same thing.

 

@peter2772000 the unlimited 4Hi speed is good to know!!! It never specified in the manual so I figured. Just wasn't possible to go any faster with the wind pushing us sideways on ice

 

Often people or EVEN FREAKING DEALERSHIPS forget to lube the drive shafts. I would check that first - even if its not it, you still need to lubricate the drive shafts - I THINK every 10k miles. I might be wrong on that, I just do mine every 5k oil change.

 

Not normal. A 4runner shouldnt make any more noise in 4hi than in 2wd.

 

Do you know the service history? I’d start by inspecting and servicing the front driveshaft. Could be the source of the noise, since it’s turning in 4hi, and not not turning in 2wd. So something could be up with that. As mentioned, those ujoints could be dry as a bone.

There is a slip yoke on that shaft as well that could be a problem. Maybe if it’s seized, it transmits the vibration as the drivetrain torques back and forth with throttle application. That slip yoke is probably only there to allow for the movements of the engine/transmission under different loads.

If greasing it isnt enough, I might even try to remove it to actually verify the slip yoke moves.

Next to check is the condition of the Front diff oil.



Or there could be a garbage bag wrapped around the shaft…you never know lol.

 

Normal.

You have more gears engaged and spinning in 4H.

It's bound to make more noise than just 2wd.

 

Really? Anybody else here running a noisy 4wd? Mine is quiet as a mouse. Do you ever notice if it’s quieter after greasing the u-joints and yoke?

 

Agree, the only way I know I’m in 4H is the light on the dash and a slight difference in the “feel” of the truck. No additional sounds.

 

I have no noise. Like i previously said. I make sure every bit of maintenance is done by doing it myself. I’m new to Toyotas but I did read the owners manual and the importance of making sure your drive shaft is greased.

 

My friend the noise on 4wd hi is normal , you must need to replace oil of transfer case and rear/front diff according to the Toyota specifications , 4runner or body on frame vehicles require too much maintenance if yo careless this will not last long .
4wi is good thing to use and this will save you from accident in rain and snow if you drive in a straight line , because front diff is different then rear its open but they are kind of lock with each other ,will eat your tires .
Part time 4wd , front and rear diff turn different speeds they do not communicate with each other only use in rain or snow or sand or applies condition do not use in normal conditions , 4runner limited is all time 4wd and have center diff but part time 4wd is different .
short answer , ,chill , noise is normal .

 

Not particularly.

I notice a mild hum when I engage 4wd and exercise it on the street (I’m talking 4H around 50-60mph).

I don’t notice it if I’m in 4H on a dirt road going 30mph.

 

I have to wonder if that slip yoke has something to do with transmitting sound. The rear slip yoke can be tricky greasing just right. And even though I hit them frequently with grease, I know my rear one sticks it if it’s under-greased (it thunks/kicks when you come to a stop).

The front slip yoke hardly has to do anything compared to the rear, since the driveshaft connects to a hard-mounted diff. But, I imagine it has a slide yoke there to accommodate torquing movements of the TC anc Diff in their rubber mounts. If the slide yoke is stuck, I bet it transmits more vibes/noise.

When it gets warmer out, I plan to figure out how to grease these yokes properly, since I’ve been shy with the grease in order to avoid blowing out the seal. Judging from the kick/thump in the rear, I’m pretty sure I’ve been under-greasing them.

 

I’ve greased the yokes many times. Starting with about 6 full pumps the first time. Then 2 or 3 pumps at each ~5000 mile oil change. I wipe all excess grease off before re-greasing and I can see where it’s oozed out a little along the yoke at the next service.

 

Here is the question I have to those driving 50-60 mph in 4WD. Why? If you’re going that fast then I doubt you need 4WD.

 

THIS.

 

I’ve never got grease to come out of the seal on the slip yoke…so yeah, probably undergreasing mine. If yours are well maintained, then my theory is out the window lol

 

If I'm going to work on a completely snow covered highway and the traffic is moving 50-60 I lock it in. Might not need it but if you do it's already in, If you don't have it locked and need it,
hard telling how long it will take to lock up. Not like the good old days with the straight axle you could run with the hubs locked, let off the gas, yank the lever back and have instant 4 wheel drive.
Or you could just run 30 miles an hour and be the biggest hazard on the road.
I ran it over 400 miles straight in 4 wheel last deer season coming back from the Upper Peninsula.
Bought it to use it. Always done the same with my Chevy and Ford trucks, never a problem.
Hopefully Toyota isn't any different.

 

Mine isn't "loud", but it certainly has its own sound when 4H is engaged.

 

Because it's safer in sketchy conditions. 1:45 to 4:30 below.

 

I agree that mine seems to have its own little rumble.

 

One of my Toyota Service Managers frustrations is new 4Runner owners who expect Lexus quiet when 4WD is engaged. 4Runners are factory equipped with a robust 4WD system. When you factor in some of the other traction components that have to work with that system, it’s a tribute to the engineers that a 4Runner is as quiet as it is.

 

It's recommended that you "exercise" the 4wd system for roughly 10 minutes once a month.

So if I'm not making it to the trails frequently enough, I'll put it in 4H on a straight highway and switch into 4L in my driveway.

 

I have a 2022 and in 4H it definitely has a louder noise or maybe different is the right word. It is almost as if the engine idles different but doesn't show a difference on the tach.

 

This truck on pavement in 4H sounds the same as 2H, there is a difference in steering feel which is slightly heavier or more controled. Often wondered if some years of 5th gen had tighter spec components, this 2014 at 130k miles drives and feels like a new vehicle.

 

Mine sounds no different in 4H than in 2H