Rear Wheel Bearing or Diff Noise?

Recently I have started to notice a noise coming from the transmission somewhere. It seems more noticeable when just coasting to a stop in neutral, doesn't seem as obvious if still in gear. I jacked up the front and eliminated that end. The rear however sounds noisy, I can't say I have ever noticed this before so I am thinking it is a new development (but could be wrong?) I disconnected the rear prop-shaft from the diff to try and pinpoint the sound and wondered id it was a wheel bearing, but the noise can be heard from both sides, so could it be the diff? There is no play in the wheels and I have checked the thrust play in the bearings as per the WSM.

 

Here is a video I took spinning RH then LH rear wheels, the video seems to have picked up the sound very well and makes it seem louder than it actually is.

Is this normal and I'm only noticing it for the first time?

youtube.com/shorts/P8N1twerWbQ?feature=share

EDIT: It was serviced at the Suzuki dealer at the end of December and has done 800 miles since with 41,000 miles on the clock.

It is from the diff and it is to some extent normal, or at least, I've heard it on multiple cars that I have owned and it has not been a problem on any of them.

Am I correct in thinking that you have both rear wheels off the ground and as you rotate one the other is rotating in the opposite direction?

I don't know how familiar you are with the "innards" of the differential - the two side gears, and depending on the differential, two or four differential pinions, all bevel gears with chunky "straight cut" teeth, because they are straight cut there's a fair bit of "back lash" between the gears. It's actually a very crude affair, there are no bearings, the diff pinions run directly on the cross pins,



Under normal operation, the entire unit rotates as a single assembly, and because the gears are not rotating relative to one another they make no noise, when you're turning a corner is when the "differential action" occurs, and the gears rotate relative to one another. generally speaking, the difference in rotational speed between the right & left wheels is very small, so the rotational speed of the gears is also quite small and the noise is rarely heard.

I'm not sure that is just the sun gears walking themselves round inside the diff. It's definitely louder on the second side shown and to me sounds more like something dragging inside the brake It's almost like a playing card in a bicycle wheel type noise. I'd have the drums off and everything inspected.

@fordem
Thank you for the information.
Initially, I just jacked up one side to listen then the other, but the had both wheels in the air when I took the video.
I have a basic understanding of what the diff does and why it is needed, I have not seen inside one in person though.
The other thing I could check is the oil level, I can only presume it was checked at the last service.

@Lambert
Perhaps it is just the normal diff noise I am hearing, and just haven't picked up on it before?
I agree the 2nd side does sound like the brake shoes are dragging a bit (thought it was my breathing when I first played it back  )
I did take the drums off yesterday and everything looked ok.

At the end of September I did the 5 wheel rotation and removed the drums then as well just to check the wear on the shoes and clean out the dust, I just don't remember hearing any noise back then. But at the service, I think they adjusted the handbrake, as it did have slightly less travel on the lever than before (not that it was excessive), maybe they have over done it as they are self adjusting drums, so shouldn't really need the cable adjusting?

The first side sounds reasonable to me which implies that either it's an effect of the recording on the second side or something is not happy.

The sound when turning could be the normal noise of the differential; however, there is another type of noise that seems to come from the outer rear bearing. What I’m going to say applies only to the third-generation Jimny; I don’t know if it’s the same for the fourth generation:Check if, when hitting the wheel, it feels loose or makes a lot of noise—this indicates a worn-out bearing. Try pulling and pushing the wheel firmly with your hands; it should not feel loose. If there is any looseness, it should be minimal and barely noticeable.The rear bearing system in the Jimny is very basic and poorly designed. If you replace the bearing, make sure it's the original one, as manufacturers do not produce spare parts with the same quality as those sold to car assemblers.The free play mentioned in the manual is almost impossible to find in a Jimny that does not have less than that tolerance, especially in Jimnys with over 150,000 km or those where the original replacement part was not used. A low-quality bearing can last between 5,000 km and 30,000 km, while the original lasts longer.Why does it wear out so quickly?

• Lubricated only with grease, not oil.
• Exposed to water and dirt, with only a semi-basic seal protecting the bearing from water and dust.
• When wading through water, it enters through the brake drum plate and gets trapped between the bearing and the plate (like a cup). Over time, the water seeps in and contaminates the bearing grease.
• Additionally, the bearings are small and have a limited surface area, making them more prone to wear, especially on rough roads at high speeds (corrugated dirt roads).
• The left-side bearing is more likely to fail or wear out first.

When replacing the bearing, it is not recommended to apply silicone between the differential sleeve and the brake plate, as the silicone will prevent water from draining through the gap between the plate and the bearing. Additionally, in case of oil leakage, the oil will escape outside the brake plate, warning you of the issue. If silicone blocks the drainage, the oil may instead seep into the brakes, reducing rear braking efficiency and causing failures in the vehicle inspection due to braking imbalance (although this does not significantly affect real-world performance, the inspection machines will detect the difference).I have a third-generation Jimny, single owner, 260,000 km, and I believe I have replaced the rear bearings at least 7 to 9 times.This is critical to determine if the bearings are excessively worn:

• Differential oil will leak through the rear brake backing plate, and you can see it just by looking behind the wheel.
• If not visible externally, the oil will contaminate the brakes internally. When removing the brake drum, you will notice everything is soaked in oil. Some minor oil seepage is normal, but if everything is wet, it is an indicator of worn bearings (most likely) or a faulty oil seal (though it is rare for the seal to fail before the bearing). Generally, oil leakage occurs due to bearing play.

Oil Leak Severity:

• No leaks inside the brake plate: The differential oil level is very low, or the bearings and seals are recently installed or barely used.
• Minimal seepage inside the brake plate: Acceptable, indicates a good seal, meaning the bearing is either in good condition or its wear is within acceptable limits.
• Small oil leak that stains the brakes or the outer part of the brake plate: A sign that the bearings should be replaced soon, representing a latent risk for long road trips or expeditions.
• Significant oil leak, staining the rear wheel and leaving oil on the ground: This indicates that the bearing is likely severely worn and should be replaced immediately to prevent catastrophic failure.

Catastrophic Failure:

• If the bearing wears out enough, it can break apart, causing the wheel to gradually seize up or the axle to come completely loose along with the wheel.

Symptoms of Catastrophic Failure:

• Loud noise from the rear, noticeable when manually pushing the Jeep or moving it at low speeds.
• Immediate loss of power, as the axle disconnects from the differential. Look immediately in the rearview mirror to check if the wheel is shifting outward—stop immediately before the entire axle comes out.
• Although it's rare for the axle to come completely loose (as it will make a lot of noise beforehand), this is still a possibility. I have seen cases where the axle has come off entirely.

How to Install the Bearings:

• Install ORIGINAL Suzuki BEARING and RETAINER RING, not aftermarket replacements.
• Press-fit the RETAINER RING with a hydraulic press, COLD, do not heat it.
• Do not apply silicone between the brake plate and the differential sleeve, put new oil seal.