A few questions for the experts (rear differential)

[randyusc5]

I just recently purchased a 2002 Explorer XLS 2wd 4.0L V6. Upon the test drive, I did not notice the humming coming from the rear differential as I later heard it after I already paid for the car. It is not that bad since I didn't notice it at first, but it is definitley there and I would like to try to fix it before it gets worse. I've done some reading about this problem, but I still have a few questons that I would like answered.


From your experience, what is the best 75w 140 synthetic oil brand used to minimize or get rid of the hum in the rear differential?

How many quarts of the oil does it take to refill the rear differential?

What is the best friction modifier brand that I should use when replacing the oil?

And finally, if this doesn't do anything, how long will I be able to drive the car like this because I have no money to replace the rear end?

Thanks for any help.

 

[Elessar65]

you should be ok driving it if its just a hum. there isn't a recall on it to my knowlage, just a TSB. As far as good syn oil, i personally use Mobile 1, but Lucas, Amsoil, Royal Purple, etc., are all good oils. I'm not sure about the amount of oil it takes, mine takes about 3 quarts, but i have a custom diff cover with a higher fill plug, and its a different differential than yours. i know there is a page on here somewhere with all the specs and capacities by year. try a search for it.
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[jscheier]

I run Redline in the Explorer - 75x140 (not the NS) which already has friction modifier in it. I believe it was 2.5 quarts for the 8.8 differential.

On the hum, is it constant? Is it only on acceleration or deceleration?

I'd probably change the fluid first ($25 investment if you do it yourself) and see if that remedies it. If not, pulling the cover and checking the lash and runout is next, but you'll need a dial indicator for that (as well as some past to check the gear pattern).

If the hum is constant, it could be rear wheel bearings (common) or even the final drive bearings (crapped out on our 2003). More money to repair those.

 

[Elessar65]

X2 if you do a search for your symptoms i know there a zillion threads on this, as its a common enough problem that Ford issued a TSB on it. maybe look up the TSB too and see what it says.
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[randyusc5]

It really doesn't become noticeable until about 30+ mph, but when I decelerate, I hear it all the way down until I come to a stop. I have gone through alot of the other threads on this, I just wanted some specific answers to my questions. I am going to change the oil because I believe that it is now running a 70 90 or whatever in the rear.

Thanks again

 

[skeeter123]

I've got a 2002 XLT 2WD with the 4.6L v8, with the limited-slip differential. Make sure you have the limited-slip, otherwise you don't need the friction-modifier. Mine has had the "hum" for about 70K miles now. Changing diff fluid helped a bit but did not eliminate the hum.

Check out this link:

http://www.explorerforum.com/forums/...r+differential

somewhere in that link there's a table with "door codes" that will tell you which differential you have.

I used Mobil 1 75w140 "LS" oil with friction-modifier already included; it was real expensive ($18/bottle) and I used 1 1/2 bottles. I did this at 145K miles and hopefully won't have to do it again.

Hope this helps.

 

[jakedrew]

With my 04 this is how i noticed the hum.

It would only do it after the fluid was good and warm.

I would go 50 and hold it there and it would hum, let off the gas it go away, hit the gas (lightly) and it would hum, let off, hum went away.

Ford shop charged me 1100$, well my extended warrenty covered it, so i payed 100$

good luck.

 

[EasyRhino]

My 2002 Limited V8 4WD, bought new, has had the rear end hum since about 1000 miles, no kidding.

Now 8 years later is at 104K miles and makes the same noise, no change, no louder or quieter. I'm driving it until it grenades.

So I think that you can go about 103K miles minimum.

I changed the gear oil to the Mobil 1 75W-140 that comes with the friction modifier in it at 100K miles. Made no difference in the noise, or in any other way as far as I can tell.

 

[mountaineer02]

The TSB 05-23-3 is what your looking for, its a revision of a previous TSB. I went to dealer to see what and how much it was. Its pretty much a whole new rear end for 400$ just parts, another6.6 hours labor at dealer rate. I just replaced my lube yesterday, will see how it holds up? Oh theres a TSB for the wheel bearings aswell.

 

[miker104]

Also a TSB for rear seals if you have the IRS.

From what I have seen on this version of the Explorer its a piece of junk. Transmission is POS too. Seat belts get trapped and fix is $45 kit with two pieces of tape an a couple of hours of labor.

I see the auto industry has learned from aircraft manufacturers if it is a bad design issue a Service Bulletin and if out of warranty make the customer pay.