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Noise From the Rear


February 19, 2010
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Year, Model & Trim Level
2002 Mercury Mountaineer
:thumbdwn: when coasting at around 45-50 mph, i hear a humming noise from the right side. Originally I thought it was coming from the front passenger side. Mechanic said it sounds like the rear. It also happens when turning left, i guess its putting pressure on the right side. when i turn left the humming stops. What could be the problem. The rear diff has recently been serviced. Thanks

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How many miles does the truck have just out of curiosity. And when you say the rear has been serviced...what did that service include, and what was the problem with the rear in the first place? How long ago did this service take place?

It can easily be misconceived that a bad front bearing assembly is diagnosed as a bad rear bearing...happens more often than not. The ear can be deceiving...especially when you're doing 45-50MPH...sound travels, and it's a short wheelbase.

The bearings on these trucks are known to fail around the 100k mark, it just happens. I did my fronts at 120k miles, even though they showed their ugly head around the 110k mark...

My rears actually need to be changed as well, I'm just not in the best location right now to do them...but as soon as my workshop is completed at my new home and I can access my tools, I am going to do my rears. Truck is now at 133k miles.

The truck currently has 94k on it, the rear diff service included a fluid change. never had any bearings changed. Is this a wheel bearing hub or just the bearings? whats this gonna cost me? thanks

The truck currently has 94k on it, the rear diff service included a fluid change. never had any bearings changed. Is this a wheel bearing hub or just the bearings? whats this gonna cost me? thanks

The front is a complete sealed hub/bearing assembly. The rear utilizes a separate wheel bearing from the hub, which has to be pressed in and pressed back out. It is advisable to put a new hub in the rear when you change the bearing, most auto parts stores sell it as a complete assembly, which still has to be machine pressed in...however you can buy the rear wheel bearing separately.

When you said that your rear end had been serviced, I thought you were referring to a rebuild or replacement of the diff clutch pack and/or ring and pinion. Rear differential hum is quite common a search.

A quick and unrefined (and free) way to check a wheel bearing is to jack up the wheel in question...try to wobble it back and forth and up and down. If there is have a bad bearing. Whether that's the source of your sound...have no idea. However if the sound is prevalent when you turn your wheel and goes away when you turn it the other way, that sounds like a bad wheel bearing. Now you just need to find out which one it is....

As far as how much it costs? Well...the parts are about $150 per wheel your cost, as far as the labor, expect to pay the labor rate for 2.5-3hrs of shop time per wheel...or you could do a search on here and there are plenty of write ups and discussions regarding the replacement of wheel bearings and hubs, as it's quite a common issue around the 100k mark on ALL explorers. With yours approaching 100k, it's pretty feasible that yours are going bad.

Rear Noise

I've had both rear bearings replaced on mine. Currently at 138K miles. I found a transmission repair shop and they did it for around $280. Ford dealer did a diagnosis and told me the fronts are needing it soon too.

Now would the humming be something to be concerned with or is it normal? Maybe an additive by Lucas Oils would help the humming noise if it is the rear diff. Thank you for all your info!