Change differential fluid???

[Mounty99]

I've never changed the diff fluid in my 1999 Mercury Mountaineer 5.0 AWD (193,000 miles). And this includes the transfer case..which I assume is really the center diff. The reason is I was told not to do it. And the Haynes Manual (section 1:17) seems to back this up:

"On 1997 and later models, the differential is "lubricated for life" ,and does NOT need to be changed, except under very extreme usage or if submerged in water."

Now, I've noticed a ton of people on this board seem to change it out as part of a routine maintenance. So, what's the right call here? I love my Merc, and want to do what's best for her!

Thanks for any suggestions.

 

[crunchie_frog]

Well, I would definitely change the transfer case fluid, easy, regular Mercon, cheap and important. I also think you should change both the front and rear diff fluid as well, just for peace of mind. Likely they will look okay, but the parts these fluids are lubricating are the parts that are delivering all of the power of your vehicle to the road so it seems worth it to me to change them. The front fluid is easiest removed with a vacuum set up. For what it is worth, I have 3 of these 5.0 AWDs, and all of them respond well to TLC, like keeping fluids in good condition. I think 300K+ miles is not an unreasonable expectation for these vehicles, the engine and trans are very reliable.

 

[bill06447]

The front and rear diffs are factory-filled with synthetic, so if it's not leaking there's no reason to top it off, and the synthetic doesn't "wear out" per se, hence the "lifetime" moniker. But if the vent hose (with screen!) has ever come off then it's been compromised, but either way I would change fluid in any used vehicle I had recently purchased since I don't know the history.

Bill

 

[bluestream1]

Lubricated for life is a joke. Life of what? Ford warranty maybe?

As for synthetic never wearing out, no oil ever wears out, it just becomes contaminated and thats why you change it. The rear axle should be changed, but it should have been done long ago. You need to use 75W140 for sure on one with high miles. The oil in there now will be thick from oxidation.

All front diffs are not factory filled with synthetic.

 

[Flash]

The 3 transfer cases that I have changed the oil in have all had extremely dirty fluid in them. Change the fluid.

It's not that expensive to buy enough oil to do the diffs so do it anyway.

And what bluestream1 said about "lifetime". I'm sure Ford would prefer that we buy a new car than to be caoxing 20+ years out of these things.

 

[BKennedy]

A buddy I know owns a transmission shop. He says you only need to change the fluid of the parts you don't want to replace.
He recommends changing the fluid in the transfer case, transmission and differentials at least every 50,000 miles regardless of what the manufacture recommends. I met him while he was replacing the transmission in the Volvo we had after 102,000 miles. It was supposed to be lubricated for life.
If you are towing or off-roading your vehicle, then you should change the fluids even sooner.

 

[Mounty99]

Sold!! Now, what's the best way to do this? Please keep in mind this will be my truck's first diff/transfer case fluid change EVER (193,000 miles).

(1) Do I need to buy any special tools? MityVac 7201, etc...
(2) Should I go with Amsoil, Royal Purple, Mobil 1, etc??
(3) On the rear, is it ok to just suck out the old fluid, or would you recommend taking off the cover and cleaning everything thoroughly?
(4) Transfer case: motorcraft ATF?
(5) Front diff: 75w90?
(6) Rear diff: 75w140 w/friction additive?

Thanks for all the help and advice.

 

[bluestream1]

Do you have Trac-lok in the rear? I used redline 75W140 and it has the additive in it.

Take the cover off the rear and let it drain. ALso do visual inspection.

I use Mobil 1 ATF in my transfer case. but Mototcraft TC fluid is fine

Use 75W90 in the front. Conventional is fine

 

[Mounty99]

Do you have Trac-lok in the rear?

Thanks for the reply. I don't know if I have Trac-lok or not?

Do I need to buy any special tools? MityVac 7201, etc...

Can I get off ALL the drain/fill plugs with a normal ratchet set, or do I need a special tool?

 

[shadowless127]

Doesn't the front diff require ATF not gear oil?

 

[1998Exp]

Why guess (incorrectly) when you can open the driver's manual and check for yourself?

Doesn't the front diff require ATF not gear oil?

 

[shadowless127]

Why guess (incorrectly) when you can open the driver's manual and check for yourself?

Because it was easier to post considering i'm at work inside my office and cant get to my owners manual and am trying to price out all the stuff for all the work i gotta do on my X...

 

[swshawaii]

Pages 256-259

http://www.fordservicecontent.com/Ford_Content/catalog/owner_guides/01expog1e.pdf

 

[crunchie_frog]

Mounty99

My $.02, if you are at all concerned about your parking brake shoes/springs these are most easily done (IMO) with the axles removed which of course means rear diff cover removed. So, if you are going to do the rear diff, that would be the time for parking brake shoe/spring work if needed.

My memory is you need a 3/8 ratchet short extension for drain plugs. The extension or ratchet end goes into the drain plugs.

 

[shadowless127]

Pages 256-259

http://www.fordservicecontent.com/Ford_Content/catalog/owner_guides/01expog1e.pdf

Good looks, will deff download and save this.

Wish it told you the amount needed and not just what type, though.

 

[swshawaii]

Wish it told you the amount needed and not just what type, though.

Page 256 (Capacities and specifications)

 

[bluestream1]

I think you need 2.7 Liters. Keep in mind that a full axle is 1/2 inch fluid below the fill hole.

Just byt the Redline or similar that has the LSD addative already in it. If you dont have trac-lok you can still use the ssame oil as the LSD

 

[Mounty99]

*OP here*
I'm glad some people now have the Ford manual, but if I listened to Ford, I wouldn't be doing this rear diff anyway. I'm trying to find out what's optimal for my Merc's longevity...in lieu of what Ford is telling me to do.

Thinking I might go all Amsoil. Would there be any problem with synthetic, considering my truck has 193,000 miles and original diff/transfer case fluid? I heard that synthetic can do too good of a job cleaning stuff in these high-mileage cases and cause some issues.

I'm not opposed to running some non-synthetic in there for a short time, then replacing again with the Amsoil for the longer term...if this would be helpful?

Thanks.

 

[Mounty99]

Well, I would definitely change the transfer case fluid, easy, regular Mercon, cheap and important. I also think you should change both the front and rear diff fluid as well, just for peace of mind. My memory is you need a 3/8 ratchet short extension for drain plugs. The extension or ratchet end goes into the drain plugs.

Thanks. And thanks to everyone for your input. Gonna get this done over the weekend. I'm not best mechanic...so hoping for the best. Will let you know how it plays out!

 

[Mounty99]

One more thing. Looks like people jack up front to help with draining. Does anyone then jack up the back when filling to help put a little extra fluid back in? :scratch: