Rear end noise can come from several different places.
A wheel bearing can make noise.
A tire can make noise.
Driveline components can make noise.
And sometimes the problem is inside the differential itself.
That is what happened with this 2010 Nissan Xterra.
The rear end had developed a significant noise, so the differential cover was removed to see what was actually happening inside.
What came out gave us the first big clue.
There was a large amount of metallic material on the magnetic drain plug.
The Metal Was More Than Normal Wear
Differentials naturally create some fine metallic material over time.
That is one reason many drain plugs are magnetic.
But there is a big difference between a light coating of fine material and the amount found in this Xterra.
The magnetic plug was covered with metal.
That immediately told us the internal components deserved a much closer inspection.
The Ring Gear Showed Visible Damage
Once the differential was opened, the internal inspection found more evidence.
The ring gear showed visible pitting on the gear face.
The technician also identified substantial noise consistent with a failing rear pinion bearing.
There were no large broken chunks of gear found during the inspection, but the amount of metal, the visible pitting and the bearing noise all pointed in the same direction.
This was not simply old fluid that needed to be changed.
The differential had internal wear and bearing damage.
Why the Xterra Came to Shoreline
The first internal inspection was completed at 34th Street Garage in Seattle.
Once it was clear that the rear differential needed major work, the Xterra was transferred to Chuck’s Auto Repair – Shoreline.
There was a specific reason for that.
Mark, one of our master mechanics at the Shoreline shop, has more than 40 years of experience and has performed this type of repair many times. He has also rebuilt many differentials by hand over the years.
This was exactly the kind of major drivetrain repair where that experience mattered.
The earlier inspection had also found that an appropriate rebuilt replacement assembly was not readily available.
At Shoreline, the final repair plan became a complete new Nissan rear axle housing and differential assembly.
Seeing the Original Differential in the Vehicle
Before the old assembly came out, we had a clear view of the original differential still installed in the Xterra with the cover removed.
That gives a good sense of what is actually involved.
The differential is not a small bolt on component sitting off by itself.
It is part of the rear axle assembly and has to handle engine torque while allowing the rear wheels to rotate at different speeds when the vehicle turns.
When the bearings and gear surfaces inside begin to wear, the noise can become the symptom that leads to the real problem.
The Final Repair Used a Complete New Nissan Assembly
Instead of trying to keep the worn differential in service, the final repair used a complete new Nissan rear axle housing and differential assembly.
That meant replacing the major rear axle and differential assembly rather than treating the metal in the oil as a fluid service problem.
The new unit arrived as a complete assembly and had to be positioned and prepared for installation into the Xterra.
This is a substantial repair.
The axle assembly supports the rear wheel ends while also carrying the differential and the internal gear set that sends power to the rear wheels.
A Major Repair Starts With a Good Diagnosis
The interesting part of this repair is not simply that the Xterra received a large new assembly.
It is how the decision was reached.
There was rear end noise.
The differential was opened.
Metal was found on the magnetic plug.
The ring gear showed visible damage.
The bearing noise supported the internal wear diagnosis.
Only then did the repair move forward.
That is the difference between replacing an expensive part because it might be bad and replacing it because the inspection gives you evidence.
The New Assembly Was More Than Just the Center Section
The replacement assembly included the rear axle housing and differential rather than only the internal center section.
That meant the job involved far more than opening the cover and replacing a few small parts.
The complete assembly had to be handled, positioned and installed correctly.
The differential was then filled with the proper gear oil as part of the repair.
What Does Differential Failure Sound Like?
There is no single sound that proves a differential has failed.
Drivers may describe rear end noise as:
a whine
a howl
a rumble
a growl
or simply a new noise that changes with vehicle speed
The sound by itself is not the diagnosis.
The useful next step is determining where the noise is coming from and then inspecting the components involved.
On this Xterra, opening the differential provided physical evidence that matched the noise complaint.
Why Metal in Differential Oil Matters
A small amount of fine metallic material can accumulate during normal gear operation.
Large amounts are different.
Metallic debris can be evidence that gear or bearing surfaces are wearing.
That is why the plug, oil and internal components all have to be considered together.
On this Xterra, the amount of material on the magnetic plug was only one part of the diagnosis.
The ring gear damage and bearing noise added more evidence.
Why Experience Matters on a Major Drivetrain Repair
Modern diagnosis often involves scan tools and electronics.
Mechanical experience still matters too.
Differentials use bearings, gears, preload, clearances and precise alignment.
Someone who has spent decades working with them develops a feel for what normal wear looks and sounds like and what deserves deeper attention.
That was one reason this Xterra was sent to Shoreline.
Mark has spent more than 40 years working as a master mechanic and has rebuilt many differentials by hand.
Even though this repair ultimately used a complete new Nissan assembly rather than rebuilding the original differential, that background was valuable in handling a repair of this size.
What Should You Do if Your SUV Develops Rear End Noise?
Do not assume every rear end noise means the differential is failing.
There are other possibilities.
But if the noise is new, getting louder or changing with vehicle speed, it deserves inspection.
The sooner the source is identified, the better the chance of understanding what is happening before the condition gets worse.
On this Nissan Xterra, the noise led to an internal inspection.
That inspection found metal.
The metal led to a closer look at the gears and bearings.
And that evidence ultimately led to replacement of the complete rear axle and differential assembly.
That is how a sound becomes a diagnosis.
NISSAN XTERRA DIFFERENTIAL FAQ
What did the shop find inside this Nissan Xterra differential?
Inspection found a large amount of metallic material on the magnetic drain plug, visible pitting on the ring gear and noise consistent with a failing rear pinion bearing.
Does metal on a differential drain plug always mean the differential needs replacement?
No. Some fine material can be normal. The amount and type of metal need to be considered along with the fluid condition, gear surfaces, bearing condition and symptoms.
Was the original differential rebuilt?
No. A rebuild was considered during the earlier diagnosis, but the final approved Shoreline repair used a complete new Nissan rear axle housing and differential assembly.
Why was the Xterra transferred to Chuck’s Auto Repair – Shoreline?
The vehicle was sent to Shoreline for the major repair because Mark has more than 40 years of master mechanic experience, has performed this type of repair many times and has rebuilt many differentials by hand.
What was replaced?
The final repair used a complete new Nissan rear axle housing and differential assembly along with the required gear oil.
Can rear differential noise be confused with other problems?
Yes. Tires, wheel bearings and other driveline components can also create rear end noise. Inspection is needed to identify the actual source.
DIFFERENTIAL AND DRIVETRAIN REPAIR IN SHORELINE
If your truck or SUV develops a new rear end noise, we can inspect the driveline and explain what we find.
Chuck’s Auto Repair – Shoreline
14501 15th Ave NE
Shoreline, WA 98155
206-368-0980
Schedule through the current Book Online / Schedule Appointment here.