To do a rear differential oil service or not?

[chefduane]

3x, do a search on "u-joint" or "universal joints" and you will find a thread about, uh... u-joints. I had a similar sound that developed in my '98 and after doing some diagnostics found that it was the rear u-joint failing. I replaced both front and rear at that point and all was well. I think perhaps that might be your problem.

 

[SupaSwope]

I actaully have bought all the parts to do similar job on mine. Bought new bearings, seals, parking brake hardware, shoes, fluids, gasket, axel shaft dampner, sway bar links and bushings, and shocks, pretty much everything but the leaf springs. Also got new tires but haven't put them on yet. Was planning on shooting a how to video.

 

[imp]

Our 8.8" Ford differentials are well known for developing a whine under load at somewhere between 100K and 150K - most likely due to wear of the ring/pinion gears or the pinion bearings. Mine developed that whine at the latter number, at which point I changed the oil to good quality synthetic (noticing some silver-colored metal flakes in the old oil). Wondering whether changing it earlier would have made any difference. Put 10K on it since, and things are not getting any worse, but I will, at some point take it apart and replace what needs to be replaced.

@1998Exp
I have 160K, diff never touched, original oil. Whine (slight) appears on and off, only at highway speed, usually upon an increase in power needed, up a hill, disappears downhill. This has gone on, never worsening, for maybe 30K now. Interesting it corresponds to the numbers of your experience.

Bearing preloads are definitely very important, and definitely do change. Most highly stressed: pinion bearings, so they're preloaded most. Interestingly, new bearing install is preloaded higher than old bearing replaced, per Ford Shop Manual. I would be willing to wager that for cases like mine, slight whine coming and going, a tooth contact check would reveal acceptable pattern, yet worn-out parts "give" enough to allow slight misalignment to produce noise. Unfortunately, we can't check contact pattern under load! Some days, driving the same route, no whine is noticeable.

Keep in mind, contact pattern is not the only cause for whine. Good pattern on scored or abraded tooth faces howl like hell! Been there! imp

 

[CDW6212R]

FYI, these comments remind me of my Mercury's history. I bought it at 98k miles, and changed the differential within two months. I have a Torsen in it, and used Severe Gear 75-140 from then. Fortunately this was the first time a new differential didn't require different side shims to correct the backlash. It was .009 immediately using the original side shims(spacers/plates(whatever they are called)). I have changed the gear oil once since then, maybe at 155k or so. It's at 207k now and has never made any noises. I'd bet the bearings are still good, the pinion bearings being original parts.

In an enclosed system, any wear or debris will eventually create issues or symptoms. That's why an automatic trans is critical to have clean ATF, no material in it etc. A trans can go indefinitely if the fluid stays clean from ideal shifting(not slipping/wear). Dirty ATF is a sign that there is wear happening. The rear differential is similar, it simply has less parts, and more robust stronger components. Keep it clean and the clearances right, they can go for ages.

 

[Centaurus5.0]

3x,

Use Motorcraft XL-3 Friction Modifier or Ford Racing M-19564-A Friction Modifier. They are they same.

I've used Amsoil's and Lubegard's modifiers in the past and the rear was still chattery around corners. I've never had that problem when I use Ford's smelly stuff.

I'd also recommend to you the 75w-140 weight as other have. It should keep it bit quieter.


This TSB may be informative:

http://mygtcs.com/mustang/documents/tsb/tsb04-24-20.pdf

 

[imp]

@Centaurus5.0 ....."and the rear was still chattery around corners."

The Torsen differential, by design, can't do that. Many times, messing with Detroit Lockers (no Torsen available for the diffs I worked with), I wished I had one! imp

 

[Centaurus5.0]

Yessir

I was talking about high mileage Explorers that still had the factory LSD clutch packs installed.

And yes, Torsen's and TrueTrac's are nice.

 

[CDW6212R]

BTW, the gear oil called for is the synthetic 75-140 for the rear. I like that they require that, it's the best protection.

With the Severe Gear, I've used the 75-110 in the rear, and the thinnest in front, for a low stress application. Al did that also for his 99 Explorer for fuel economy. If in doubt, use the 75-140 for sure.

 

[Centaurus5.0]

I got that weight from the TSB:

"Refill axles with 4 oz. Friction Modifier (XL-3) and
the necessary amount of Rear Axle Lubricant
XY-75W140-QL, regardless of the axle lubricant
originally used in the axle."

80w-90 was originally recommended by Ford for 8.8. Then 75w-90.

As long as its changed, any weight or quality lube in there is better than the old stuff, i reckon.


I had some older Amsoil 80w-90 around so i decided to use it up in the Cent or else id be using Severe Gear 75w-90. If I got a rig with 150,000+, i'd too go with the 110-140 weight.
It got annoyingly chattery with the lube only so instead of putting in Ford XL-3 I squirted in (more experimenting) a 1/2 oz. of nanolub WS2.

It's perfect now. It grabs when doing sharp turns on loose gravel but silent and smooth on pavement.

That is except the bit of whine, which sounds like is normal.

 

[Centaurus5.0]

Hey Don,

Where are the Registry's for your rides? I find the lack of pictures of your toys on ExplorerForum........disturbing.

 

[CDW6212R]

Sorry, I often think of 90-140 as the gear oil viscosity, I meant 75-140. There are so many variations it's hard to think of them quickly.

My rides are all rather normal looking DD vehicles right now. My parts scattered around my garage, shed, and spare room would be worth a hording episode. I'm hoping to go pick up a special rare GTC body kit for my Lincoln soon, it's nearly 500 miles in NC. So my signature is about as impressive as I have right now.

My avatar shows my Mercury as it is, and close to what my 98 Limited will be painted like, maybe this year. This is what it looked like when I got it, thus I named it Black Coal for now. It's dull flat black on portions of it.

View attachment 96696

 

[3xowner]

Well, the service is done... while replacing the fuel pump s/u assembly I decided to knock this diff service out.

changed it with motorcraft synthetic 75w140 (xy75w140QL) and motorcraft friction modifier XL3.
picked them up at dealer for $22.06 per qt and 6.70 for 4oz bottle. the gear oil was cheaper there than anywhere else I had found... even walmart was about $25 a quart,

used less than 1/2 a 3oz tube of Versachem's mega black for the gasket... followed Chris Fix's youtube video on rear diff service .... laid the silicon RTV down, let it set up 10 mins to be tacky... bolted up the top and bottom... got all bolts in to a good depth, let it sit for an hour, then torqued it down. I found specs are 20-25 ft lbs so I set my wrench at 23. I let it cure overnight for about 14 hours then added in the fluid.

Yep, the garage sticks now to high heaven from that gear oil.

i thought specs called for 5.5 pints (2.75 qt)... i used nearly all 3 qts plus the 4 oz additive... i would say of the 100 oz total supply I probably added 96 oz which is about over the 5.5 pt or 88 oz spec... I will check the numbers again soon.

 

[GTMountain]

I always do rear end outside. Then, the smell can dissipate plus I can use the hot AZ sun to warm up the bottles of gear oil. - If doing in cooler weather put the bottles in a bucket of hot water.

 

[koda2000]

I use a small inexpensive transfer pump to fill my diffs. It helps if the fluid is warm. The rear takes pretty close to a full 3 qts and you really can't overfill it, because it will start to spill out the fill hole when it's full. The actual amount of fluid you put in it is not really that important/critical. As stated, it's about 3 qts and when it's full it's full.

 

[UtahX]

Late to the party, but do it. I change mine at 70K intervals now.

 

[Diambel]

I have a 2000 explorer RWD with the 4.10 limited slip.

My rear differential has near been service yet, 154k miles.
I've seen ideas that it should be done at 150 and then every 30-60 afterwards...

In my owners manual i read it has 75w140 synthetic gear oil that they say never needs serviced in its lifetime except if the axle gets submerged in water. Well its never been submerged ever. They even say, don't check it ever unless a leak is present, which there are no leaks.

the job seems that it will cost maybe 90 bucks as it takes nearly 3 qts of syn gear oil which is about $25/qt, RTV for gasket, and the 4 oz of enhancement additive.

thoughts?

Thank you Found few discrepancies of info I like yours best 99 Explorer No one has ever mentioned such I do keep maintenance up 165000 mi