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2021 Ford Explorer ST Drivetrain Clunk/Thump on Acceleration

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Mike T. · rep 0 · May 25, 1:32 AM · 1 replies · solved · Question

Vehicle: 2021 Ford Explorer ST

Hello fellow Explorer ST owners,

I've got a 2021 Ford Explorer ST, and I've been noticing a distinct clunk or thump coming from what feels like the rear of the vehicle, or possibly the drivetrain, whenever I accelerate from a stop or sometimes when shifting gears at low speeds. It's a single, solid noise, not continuous.

It's particularly noticeable when I'm in a parking lot or making low-speed turns and then accelerate. It doesn't happen every time, but enough to be concerning. There's no check engine light, and the transmission otherwise feels smooth. Could this be a U-joint, differential, or something with the AWD system? Any ideas?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 1:32 AM

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ClearTheCode admin answer:

The clunk or thump you're hearing from your 2021 Ford Explorer ST on acceleration is a common symptom of several potential drivetrain issues. Given it's a performance model with AWD, there are a few components to consider.

Here are the most likely culprits:

  1. Driveshaft U-Joints or CV Joints: Worn or failing universal joints (U-joints) on the driveshaft or constant velocity (CV) joints on the half-shafts (especially rear) are a very common cause of clunking noises on acceleration as the slack in the worn joint is taken up.
  2. Differential Play: Excessive play in the rear differential gears or worn differential mounts can cause a noticeable clunk when torque is applied. This can be diagnosed by checking for play in the driveshaft where it enters the differential.
  3. Loose Suspension Components: While not strictly drivetrain, loose control arm bushings, sway bar links, or even motor/transmission mounts can sometimes manifest as a clunk on acceleration as the engine and drivetrain shift under load.
  4. Transfer Case Issues (AWD Specific): The transfer case distributes power to the front and rear axles. Internal wear or issues with its mounts could potentially cause a clunk, especially in AWD vehicles.
  5. Axle Nuts/Hub Bearings: Less likely to be a direct clunk on acceleration, but loose axle nuts or failing hub bearings can contribute to drivetrain noise.

When to see a shop: It's important to have this clunk investigated promptly, as worn drivetrain components can lead to more significant failures if ignored. Take your 2021 Explorer ST to a Ford dealership or a reputable independent shop specializing in drivetrain work. A technician will need to put the vehicle on a lift to visually inspect and manually check for play in the driveshaft, U-joints, CV joints, differential, and all associated mounts. They can also check for any diagnostic trouble codes (DTCs) related to the AWD system, even if the check engine light isn't on. Early diagnosis can prevent a small repair from becoming a major one.

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