rear diff noise while decelerating

JBDeVega · **Posted:** Wed Nov 23, 2016 10:23 am

Just fixed the front rotors on my 05 liberty with 130k on it. without that noise from the front I can now hear a low pitch whining noise coming from the rear when decelerating from high speeds. the noise goes in a "whoo whoo" pattern that seems to be consistent with tire speed. I'm guessing an axle shaft bearing is going bad, want to know every elses thoughts and also I have to drive cross country with it in two weeks so how high of a priority is it to get fixed. Once its cross country its just gona sit for a long time so ill have plenty of time to fix it then, just strapped on time now.

WWDiesel · **Posted:** Wed Nov 23, 2016 11:27 am

Not likely an axle bearing, normally when they make noise it is constant regardless of whether you are accelerating or decelerating. Also when they wear out bad enough to make noise, they usually wipe the axle bearing seal and start leaking gear oil!
Most likely a pinion bearing is worn causing your noise from your description.
Be sure and check the pinion shaft that goes into the rear differential and make sure it does not have any excess play or movement to it.
Also check oil level in rear differential and make sure it is normal level...

flash7210 · **Posted:** Wed Nov 23, 2016 11:54 am

Could be bearings.
Could also be worn gears.

Only thing you can do to check is drain the diff oil, remove the cover, and inspect.
If there are a lot of metal chips in the bottom of the diff housing, thats not a good sign.
Also look at the gear teeth for shiny, excessive or unevenly worn spots. And look at the spider gears too.
Ring and pinion problems are rare but excessively worn bearings can cause the gears to fall slightly out of alignment, creating a "whine" noise.
I'd say that chipped/mangled spider gears are more common although I dont exactly know why.

Its also possible that the noise you hear is just your tires.
If you rotate your rear tires to the front and the noise moves to the front, then you have your answer.

bugnout · **Posted:** Wed Nov 23, 2016 8:52 pm

Check the wishbone. When the ball joint starts to go, the diff can twist on accel or decel and cause the noise your hearing.

flash7210 · **Posted:** Wed Nov 23, 2016 10:46 pm

bugnout wrote:

Check the wishbone. When the ball joint starts to go, the diff can twist on accel or decel and cause the noise your hearing.

Excellent suggestion.

JBDeVega · **Posted:** Thu Nov 24, 2016 10:36 am

bugnout wrote:

Check the wishbone. When the ball joint starts to go, the diff can twist on accel or decel and cause the noise your hearing.

i was thinking about this but i have no idea how to check this other then looking at it and see if it looks worn. Im thinking maybe if i can get someone to switch it from Reverse to drive while i watch the UCA and see if has play in it.

WWDiesel · **Posted:** Thu Nov 24, 2016 11:26 am

Simple test: with vehicle on level pavement and engine OFF; put transmission in neutral with parking brake applied good and tight and have someone rock vehicle back and forth while you watch the wishbone and differential housing for amount of movement. Any excess movement should be very evident! :wink:

JBDeVega · **Posted:** Thu Nov 24, 2016 12:47 pm

WWDiesel wrote:

Simple test: with vehicle on level pavement and engine OFF; put transmission in neutral with parking brake applied good and tight and have someone rock vehicle back and forth while you watch the wishbone and differential housing for amount of movement. Any excess movement should be very evident! :wink:

So there is no excessive movement in the ball joint but i can see the pinion was rocking up and down as the vehicle was rocked back and forth. I suspect this means the bushings may be blown.

flash7210 · **Posted:** Thu Nov 24, 2016 1:17 pm

JBDeVega wrote:

WWDiesel wrote:

Simple test: with vehicle on level pavement and engine OFF; put transmission in neutral with parking brake applied good and tight and have someone rock vehicle back and forth while you watch the wishbone and differential housing for amount of movement. Any excess movement should be very evident! :wink:

So there is no excessive movement in the ball joint but i can see the pinion was rocking up and down as the vehicle was rocked back and forth. I suspect this means the bushings may be blown.

Are you talking about the pinion yoke where the driveshaft attaches?
Or is it the whole axle housing that is rocking up and down?

WWDiesel · **Posted:** Thu Nov 24, 2016 1:31 pm

JBDeVega wrote:

WWDiesel wrote:

Simple test: with vehicle on level pavement and engine OFF; put transmission in neutral with parking brake applied good and tight and have someone rock vehicle back and forth while you watch the wishbone and differential housing for amount of movement. Any excess movement should be very evident! :wink:

So there is no excessive movement in the ball joint but i can see the pinion was rocking up and down as the vehicle was rocked back and forth. I suspect this means the bushings may be blown.

As I advised earlier; sounds like your pinion bearings are worn out and yes this will cause the noise you described as the pinion gear angle will change angles against the ring gear between accelerating vs. decelerating and make a roaring or whining noise! :roll:

There are no bushings, only bearings!
Requires the disassembly and inspection of the rear differential to ascertain the exact worn bearings and replacement requirements...cannot be properly diagnosed from outside! :wink:

JBDeVega · **Posted:** Thu Nov 24, 2016 2:00 pm

flash7210 wrote:

JBDeVega wrote:

WWDiesel wrote:

Simple test: with vehicle on level pavement and engine OFF; put transmission in neutral with parking brake applied good and tight and have someone rock vehicle back and forth while you watch the wishbone and differential housing for amount of movement. Any excess movement should be very evident! :wink:

So there is no excessive movement in the ball joint but i can see the pinion was rocking up and down as the vehicle was rocked back and forth. I suspect this means the bushings may be blown.

Are you talking about the pinion yoke where the driveshaft attaches?
Or is it the whole axle housing that is rocking up and down?

The whole axle house is moving up and down, i was just saying the pinion to refer to the end of the axle housing.

WWDiesel · **Posted:** Thu Nov 24, 2016 2:30 pm

JBDeVega wrote:

The whole axle house is moving up and down, i was just saying the pinion to refer to the end of the axle housing.

OK, that helps, not the pinion bearings then! The rubber mounts at the front of the wishbone are shot! You say the ball joint on top of the differential is tight, correct?
Replace the wishbone and check the lower control arms and make sure the bushings on the ends of them are not worn out...

rear diff noise while decelerating

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