Jeep Grand Cherokee Humming Noise When Accelerating: 7 Causes & Fixes

If your Jeep Grand Cherokee has started making an annoying humming or droning noise when accelerating, you may be wondering: What’s causing this humming noise and how can I fix it? A humming or droning noise that gets louder as you press down on the accelerator is usually caused by an issue with a drivetrain component like the wheel bearings, differential, drive shaft, U-joints, axle shafts, transfer case or transmission. Identifying the specific circumstances around the noise and when exactly it happens as you drive is the key to properly diagnosing and resolving the problem.

In this detailed guide, we will explore the 7 most common causes of a humming or droning type noise from the drivetrain when accelerating in a Jeep Grand Cherokee. We will also discuss how you can accurately diagnose the source of the humming noise based on specific audible clues and when the sound occurs. Finally, you’ll find a breakdown of the steps needed to fix the issues causing humming noises when accelerating and tips to help prevent the problem in the future through proactive maintenance.

What Does a Humming or Droning Noise Indicate in a Drivetrain?

First, let’s cover the basic meaning behind hearing a droning or humming type noise that progressively gets louder as you press down on the accelerator.

This type of noise indicates that a component or components in your Jeep Grand Cherokee’s drivetrain are worn out or faulty. The drivetrain includes all the parts that transfer power from the engine to the wheels, such as the transmission, drive shaft, differentials, axles, transfer case, U-joints and wheel hubs.

A worn or damaged component in the drivetrain will often produce a humming or droning noise because it is rotating at high speeds. But the specific culprit is difficult to identify without a proper diagnostic process.

The noise gets louder as acceleration increases because the dysfunctional component is forced to spin faster. The higher rate of rotation causes more friction and vibration, intensifying the noise.

It’s important to pinpoint the precise circumstances when the humming occurs in order to narrow down the culprit. Pay attention to whether the noise is present at lower speeds or only when accelerating hard above 50 mph. This insight provides vital clues for your mechanic.

Now let’s dive into the 7 most common sources of a humming or droning noise from the drivetrain when accelerating in the Jeep Grand Cherokee:

1. Worn Out or Damaged Wheel Bearings

One of the most common causes of humming or droning noises that get louder with acceleration is worn out or damaged wheel bearings.

Wheel bearings are located inside the wheel hubs and they allow the wheels to spin freely around the axle shafts. There are two sets of wheel bearings per axle – one on the inner side and one on the outer end of each hub.

These robust bearings must withstand a lot of force and friction. Over many miles of driving, the amount of lubricant inside the bearings decreases and the internal components gradually wear down. Eventually, the worn bearings start to make noise when spinning at higher speeds during acceleration.

The hum or drone caused by worn wheel bearings often sounds like a faint rumble or growl. It may be heard when coasting but gets louder and higher pitched as you speed up. This tells you the sound is wheel bearing related rather than coming from the differential or transmission, which would be more noticeable at lower speeds or gear changes.

Damaged or worn out wheel bearings require replacement to permanently resolve the noise issue. In severe cases, a damaged bearing can overheat and seize up while driving, potentially causing a wheel to lock up. So it’s critical to have faulty bearings replaced before complete failure occurs.

2. Faulty Components Inside the Differential

The differentials transfer power from the driveshaft to the axles while allowing the wheels to rotate at different speeds when going around turns. There is a front and rear differential in 4-wheel drive Jeep Grand Cherokees.

Issues with the internal components of one differential or both can also produce droning or humming noises when accelerating. The most common problems include:

• Worn or chipped ring/pinion gears – These two gears mesh together to provide the final reduction of speed between the driveshaft and axles. If their teeth become chipped or excessively worn due to lack of lubrication, they will make noise when accelerating.
• Bad side bearings – There are two sets of bearings on either side of the ring/pinion gears that facilitate smooth rotation. Worn or pitted bearings cause clicking or humming acceleration noises.
• Metal debris inside – Small fragments of metal from damaged components circulating in the differential fluid can cause faint humming or grinding noises.

Repairing the differential requires precisely determining which internal parts are faulty and rebuilding/replacing those components. This may involve installing a new ring/pinion gear set, bearings, using high quality friction modifier additives in the gear oil and inspecting all gears for damage. In severe cases, replacing the entire differential may be required.

3. Worn or Damaged U-Joints and Drive Shaft

The drive shaft delivers power from the transmission to the differentials through a rotating shaft. The drive shaft is connected to the transmission and differentials via U-joints (short for universal joints).

These U-joints allow drive shafts to operate smoothly even when rotating at steep angles when the suspension moves. The joints must be kept well lubricated to prevent excessive wear. Seals on the ends help retain grease inside.

Over time, the U-joints and drive shaft components can wear down, causing looseness or play in the drivetrain. This looseness results in vibration and humming type drivetrain noises when accelerating. Here are some specific issues that can arise:

• Worn U-joint bearings – The needle bearings inside the U-joints gradually deteriorate with age and mileage. Excessive play allows the driveshaft to wobble, creating a dull humming or whirring noise.
• Dry, under-lubricated U-joints – Lack of grease causes accelerated wear and clicking or humming sounds during acceleration as the joints rotate at higher speeds.
• Damaged or bent drive shaft – If the driveshaft is dented or bent out of alignment, the imbalance creates rotational vibrations that get louder with speed, causing humming noises.
• Bad center support bearing – This bearing supports the weight of long drive shafts. If it wears out, the added play causes drive shaft vibration and noise.

The fix involves determining which U-joints or drive shaft components are worn or damaged. Lubricating dry joints or replacing seriously worn ones will eliminate the droning, whirring and clicking noises during acceleration. A bent driveshaft requires replacement to balance the drivetrain again.

4. Worn or Damaged CV Axle Shafts

The CV axle shafts transfer power from the transaxle differential to the front wheels on Jeep Grand Cherokees. At the outer ends, CV joints (Constant Velocity joints) allow the wheels to move up and down while preventing vibrations from damaging the drivetrain.

After many miles, the CV joints wear down and begin to click or hum during acceleration:

• Torn CV boots – The rubber boots seal in lubrication. Once torn or cracked, dirt enters and accelerates wear of the joints, causing humming acceleration noises.
• Worn CV joint bearings – The internal ball bearings and races inside the CV joints deteriorate over time, especially if lubrication is compromised. The resulting looseness creates faint humming or whining noises as the axles rotate faster.
• Joint separation – Extreme wear can cause the outer and inner CV joint components to separate partially. This results in loud clicking and acceleration humming sounds as the axle spins.

Replacing the damaged CV axle shafts is the best repair option. For minor boot tears, a mechanic may replace just the boot if the joint is not too worn. But worn or clicking joints require a full axle shaft replacement to permanently fix the noise issue.

5. Transfer Case Problems

4-wheel drive Jeep Grand Cherokees have a transfer case mounted behind the transmission. This mechanical device sends power to the front and rear differentials and allows shifting between 2WD and 4WD modes.

Like other drivetrain components, the transfer case contains several bearings and gears. Faulty bearings or gears inside the transfer case will produce humming or whining noises when accelerating, especially when in 4WD:

• Worn transfer case input/output shaft bearings – As these bearings deteriorate, it creates excess play and drivetrain vibration, causing humming acceleration noise.
• Damaged planetary gears – Cracked, pitted or misaligned gears inside the transfer case make whining or grinding noises when accelerating.
• Low oil level – Running the transfer case low on lubricant accelerates internal wear and noise.

The only ways to fix humming and whining transfer case noises are to rebuild the transfer case or replace it entirely. A rebuild involves inspecting all gears and bearings, replacing damaged components, and properly re-lubricating the transfer case.

6. Transmission Problems

Issues with the automatic transmission or manual transmission can also produce humming and whining noises, especially when accelerating at lower speeds:

• Worn bearings – The transmission contains many bearings that support rotating shafts and gears. Excessive bearing wear allows gears or shafts to move around in the housing, creating a faint hum or whine during acceleration.
• Low transmission fluid level – Running low on transmission fluid allows gears to lose proper alignment and contact, resulting in whining acceleration noises.
• Damaged planetary gears – Cracked, broken, or worn teeth on planetary gears inside the automatic transmission will create hums and whines when accelerating.
• Bad clutch components – Worn release bearing or other clutch components in a manual transmission cause whining and grinding noises.

Repairing transmission humming noises requires a professional transmission inspection and rebuild or replacement of the transmission may be needed in severe cases of gear damage or bearing wear.

7. Drivetrain Misalignment

The final cause of humming or droning noises from the drivetrain when accelerating in Jeep Grand Cherokees is subtle misalignment.

If the drive shaft is slightly out of alignment with the differential or transmission, it can result in excess vibration and noise, especially as rotational speeds increase while accelerating. Misalignment problems include:

• Improper drivetrain angles – This causes the drive shaft to rotate at an angle rather than straight on, increasing vibration and noise.
• Unbalanced drive shaft – Heavy spots on the driveshaft produce excess rotational vibrations and noise.
• Bent or damaged components – A bent driveshaft, damaged suspension parts, or subframe damage can throw off drivetrain angles.
• Loose drivetrain mounts – Engine, transmission, transfer case and differential mounts settle over time. Loose mounts allow components to misalign.

It takes an experienced mechanic to properly diagnose drivetrain misalignment issues. They will inspect for bent components, faulty mounts, improper angles, unbalanced shafts, and damage to suspension parts. Adjusting and aligning components or replacing damaged parts will stop the acceleration humming or droning noises.

How to Diagnose the Specific Source of a Humming Noise When Accelerating?

As you can see, there are a number of potential culprits within the drivetrain that can produce humming or droning noises when accelerating your Jeep Grand Cherokee. To have the best chance of a correct diagnosis, follow these general guidelines:

• Pay close attention to the exact sound of the noise – Listen for clicking, growling, buzzing, humming or whining sounds. Also note any oscillations in the noise pitch – this often indicates rotational looseness. Distinguishing these auditory clues will help your mechanic identify faulty components.
• Pinpoint when the noise occurs – Does it happen only when accelerating at low speeds in 1st and 2nd gear? This points totransmission issues. Is the hum loudest at highway speeds and less noticeable at low speeds? This indicates worn wheel bearings or other rotational components.
• Test accelerate at different speeds – Accelerating hard from 0 to 30 mph then letting off may reveal transmission problems. Speeding up rapidly from 50 to 80 mph will accentuate bad wheel bearings and other worn drivetrain component noises.
• Inspect the U-joints, axle shaft boots, and wheel bearings for excessive wear by hand and visually. Look for any signs of fluid leaks from differentials, the transfer case, or transmission as leaks indicate internal component wear.
• Have your mechanic place the Jeep on a lift – They can check for obvious looseness or play in drivetrain components. If possible, take them for a test drive to experience the humming for themselves.

Following this methodical troubleshooting process helps isolate the root cause of those annoying humming acceleration noises. Parts can then be repaired or replaced to resolve the problem permanently.

How to Help Prevent Humming Noises When Accelerating?

While drivetrain problems that cause acceleration humming cannot be avoided forever – especially once your Jeep Grand Cherokee has over 100k miles – keeping up on maintenance is key to maximize longevity:

• Change differential fluid every 25,000 to 30,000 miles – Keeping the gear oil fresh with friction modifiers ensures proper lubrication inside the differentials to reduce wear-related noises.
• Inspect U-joint boots and axle shaft boots whenever changing oil – Replace any damaged or torn boots immediately to prevent gritty contamination of joints. Re-grease U-joints frequently.
• Check for any play in wheel bearings during tire rotations or brake work – Ifdetected early, bearings can be replaced before total failure and major noise occurs.
• Address any minor drivetrain fluid leaks right away – Don’t delay repairs of oil leaks from differentials, the transfer case, or transmission. Lost lubrication accelerates internal wear and noise.
• Use high-quality drivetrain lubricants – Premium differential oils, quality grease for U-joints, and transmission fluid helps protect internal components. Consult your owner’s manual for proper specifications.

By combining diligent preventive maintenance with attentive driving to detect any new noises early on, you can prolong the smooth, quiet operation of your Jeep Grand Cherokee’s drivetrain. But when those pesky humming sounds on acceleration do arise, use the diagnostic tips outlined here to help your mechanic get to the root cause quickly.

Conclusion

Humming and droning noises that increase with acceleration are usually signs of worn drivetrain components in your Jeep Grand Cherokee. But identifying the specific faulty part is essential to making the proper repair. Hopefully this detailed guide has equipped you to diagnose wheel bearing issues, worn differentials, damaged U-joints and axle shafts, transfer case problems, transmission wear, or drivetrain misalignment issues.

Catching and correcting small problems early on through diligent maintenance helps avoid major breakdowns and costly repairs down the road while keeping your ride quiet and smooth for the long haul.