Why Does My 4WD Whine? The Shocking Reason You Can’t Ignore!
Why does my 4-Wheel Drive whine? In most cases the problem can be any of the following components:
- Front differential Gears
- Differential fluid low
- Driveshaft U-joints.
- Transfer case wear
- TC’s low oil levels
- The front Vacuum hub assembly leaking
After 20+ years of offroad experience and owning a variety of 4x4s, I can assure you I’ve had my share of strange noises. So, I can attest it’s not always a quick fix and as you can see, there are quite a few reasons why your 4×4 is emitting a whining noise when you engage 4H.
Some other reasons could be mismatched front and rear tire diameter, low transmission fluid, or worn wheel bearings. These, however, will whine and hum in 2H mode as well, so I won’t discuss them in this article.
Next, we’ll diagnose the problems further and cover the possible causes and components that could be affected.
So far we established that the humming noise is only prevalent once 4WD is engaged and not while driving in 2H. This is because 2H mode only rotates the rear driveshaft, thus excluding the front driveshaft, front differential, and transfer case. So we can safely omit those when in 2H mode.
Whining in 2H (Rear Wheel Drive)
If you are in 2H and you still hear a humming noise it’s more than likely one of the following three components:
| Vehicle Issues | Description |
|---|---|
| Rear differential low oil | Insufficient oil in the rear differential |
| Wear on the Rear differential internal gears | Damage or erosion to internal gears in the rear differential |
| Wheel bearings (Front or rear) | Deterioration or damage to front or rear wheel bearings |
| Transmission wear | Degradation or damage to transmission components |
| Low Transmission oil levels | Inadequate transmission oil levels |
These are only applicable when selecting 2H mode, which is what you will be in most of the time since it’s designed for high-traction surfaces such as tarmac, concrete, and highways.
Let’s look at the possible culprits in more detail now
Whining Noise in 4WD (Front Differential Gears)
The front differential function is to allow the transfer of power to each wheel in front. When the 4-wheel drive is engaged the front differential splits 50 percent of the power it receives between each wheel.
The power will be sent to the wheel with the least resistance and the differential achieves this using a ring gear, pinion gear, and a set of spider gears all mounted inside a carrier. These are all securely fitted inside the differential and set at micro-millimeters of an inch and perfectly balanced.
- All these components are high-stress components.
- Huge amounts of torque is transferred through them each time you engage 4WD.
- All the components inside the differential should always be surrounded by the correct level of oil to lubricate and keep operating temperatures low
- Sufficient lubrication is necessary to avoid premature failure.
- A 4-wheel drive whine is the first sign of low or old oil and should be replaced immediately.
If the oil levels are low inside the differential the high levels of torque being transferred through it place more stress on the metal resulting in the current oil heating up higher than its viscosity can handle. This results in a whining noise in 4WD or a humming noise in 4WD.
Insufficient oil levels begin to break down the oil viscosity further resulting in the metal components not being protected and lubricated sufficiently. This is the cause of metal being worn off quickly and gear teeth becoming rounded creating excessive movement inside the differential.
The combination of low oil levels and wear on differential gears results in an audible whining sound when 4WD drive is engaged.
- Begin by checking the oil levels in the diffs and for any fine metal filings in the oil.
- If possible have a professional oil analysis done
- If no metal filings are found but the oil is very thin, watery, and black, it could simply indicate the oil was not changed regularly and needs to be drained and replaced with the correct differential oil as specified by the manufacturer.
Whining Noise in 4WD (Differential Fluid)
Diff oil is a lot thicker than engine oil and is specifically designed to withstand high pressure and temperature changes.
- Check your owner’s manual for the correct specification of differential oil for your vehicle.
- Ensure the oil you use protects against all the necessary friction for most synchronizers of mechanical gearboxes.
- Remember, automatic transmission oil is different from manual transmission oil and cannot be interchanged.
Whining Noise in 4WD (Driveshaft U-Joints)
These components are wear and tear items and need to be regularly inspected. They are situated at almost the lowest part of the 4-wheel drive and are very susceptible to moisture, heat damage, and knocks when driving off-road.
Before and after each off-road trip, crawl underneath your 4-wheel drive and have a look around, or drive it to the nearest suspension and drivetrain garage. Put your 4-wheel drive on a hoist and have a professional inspect the drivetrain for any damage or leaks.
Whining Noise in 4WD (Transfer Case)
The function of the transfer case is to lock the front and rear driveshafts and send equal power to both front and rear axles via the differentials. There is an extremely high level of torque that gets transferred through this component.
Engage 4WD in the following situations:
| Off-Road Terrain | Description |
|---|---|
| Muddy tracks | Dirt paths covered in wet, muddy conditions |
| Thick Sand and dunes | Areas of shifting sand formations |
| Icy, slick roads | Frozen surfaces causing slippery conditions |
| Slippery inclines or declines | Uneven slopes with reduced traction |
Pretty much any boggy, greasy, slick, or loose surface is ideal for locking the center differential. There has to be a small level of wheel slip for it to function correctly without failure.
If the transfer case is engaged under high traction surfaces such as driving on the highway or dry pavement, you seriously risk transmission windup or drivetrain binding.
- A whining noise coming from the front of your 4-wheel drive only when 4H or 4Lo is engaged could mean possible damage inside the transfer case.
- Once drivetrain or transmission windup occurs, there are massive amounts of torque that is redirected back towards the TC.
- This places excessive wear on metal gears inside the TC, Transmission, and driveshafts, resulting in damage and giving off a winding sound.
Whining noise in 4WD (Transfer Case Low Oil)
Another reason for whining sounds only when 4WD is selected is the low level of oil inside the transfer case. Old degraded oil is also a reason for whining sounds coming from below the 4-wheel drive in 4H. This should be inspected and replaced if necessary.
Before you drain the transfer case oil first refer to your owner’s manual for specific fluid change recommendations and exact TC oil specifications. The transfer case fluid should be changed every 30,000 miles especially if you use the four-wheel-drive off-road often.
Whining noise in 4WD (Front Vacuum Hub Assembly Leak)
If you drive a 4-wheel drive with manual front hubs, you could experience a humming or whining sound coming from the front once 4WD is selected. This could be caused by a cracked or perished rubber seal inside the hub assembly.
- Inspect the rubber lines for any cracks or breaks.
- The entire wheel assembly needs to be disassembled including the lower control arm and brake calipers on certain models of 4WD’s.
- Inspect all the ball joints while everything is loose as well.
Other Front-End whining Noises
Other causes of whining and humming noise in 4WD emitting from the front end are:
- If you’ve recently replaced or rotated the front tires and they are direction-specific tires.
- Also, if the front and the rear wheels are not the same diameter.
- The difference in the rolling circumference could result in a whining noise when 4WD is activated.
REDDIT & FORUM COMMENTS
My 2013 Sierra does the same thing. Not sure if its normal though. Some are doing it and some aren’t. I just changed my diff and transfer case fluids and found no metal or anything wrong. May be poor quality control on front ring/pinion setup. In any case it’s BS to spend big bucks for a truck that sounds like a 1960’s 4×4.
https://www.silveradosierra.com/threads/whine-when-in-4-wheel-drive.481746/
Driving 4wd on bare pavement is a good way to blow up your transfer case, especially while turning a sharp 90.
Looks like you’re driving a ram, so in intermittent slippery conditions flip it to 4 auto. 4 high should only be used in constant snow packed/icy conditions, or driving off road.
ALSO, You should only use 4 LO if you know what you’re doing and what it achieves, Don’t plan on going over 10-15mph when it’s engaged as it’s geared for high torque.
https://www.reddit.com/r/ram_trucks/comments/1897g8p/any_ideas_on_this_noise_only_happens_when_driving/
Helpful Resources
- https://www.silveradosierra.com/threads/whine-when-in-4-wheel-drive.481746/
- https://www.reddit.com/r/ram_trucks/comments/1897g8p/any_ideas_on_this_noise_only_happens_when_driving/
Final Thoughts
Dry components and joints are your first point to inspect if you have a 4-wheel drive whine. Also, take into account any irreversible damage that could be caused due to mistreatment or negligence. Transfer cases and transmission boxes whining are common side effects of 4-wheel drives that have towed heavy boats, trailers, or caravans for extended periods. Unfortunately, replacing the oil might lessen the whine somewhat but not eradicate it.
