02 Explorer with humming from rear diff.

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Apr 6, 2011 | 10:18 PM

J10Mike

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Joined: Dec 2005

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02 Explorer with humming from rear diff.

Hi Guys,
New to the forum. Lady friend has 02 Explorer that's humming from the rear pig. I'm no stranger around axles having rebuilt both front and rear, installed lockers, reset gears, etc in D44s, D60s, and one heavy azz D70.
Anyway, I'm thinking it's probably the pinion bearing. Meaning, the gears would have to be reset after pulling carrier and pinion gear. I can do that. I have all the tools I need.
But, would it be more cost versus down time effective to just replace the whole diff?
I have an Explorer TSM. But, I'm not familiar with the Ford IRS rear axle other that what I have read in the TSM. So, I appreciate any advice you guys can give me.
Thanks.

Apr 7, 2011 | 08:28 PM

steve(ill)

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Joined: Jul 2005

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Take it out on the road for a test and hear for yourself. I have a 2002 with 135k miles that has had the noise for 100k miles. You dont hear much below 40 mph. Loudest between 60-65 mph. Almost goes away after 70 mph. Cruse at 60 and hear it... raise you foor slightly to back off the throttle and the noise goes away ??????? Noise is gear mest. 60-65 mph seems to be the resonant frequency where it is worst. YOu can change the rear oil to synthetic, add friction modifier, etc to change the viscosity and "stickyness" of the oil as it clings to the gears. That might help. I use synthetic 75 w 140 with a tube of the friction modifier and 2/3 of the noise disapears. You can hear it now, but not objectionable.... and i know its not the bearings.