How often to change gear oil?

[Svashtar]

I guess it’s been about 6 years, when the drivers side rear wheel bearing ate into my soft rear axle (the one the dealer insisted was fine and did not have to be replaced along with the passenger side axle under the TSB while under warranty.)

So, for you guys that keep up with it, how often should the gear oil be changed? I have a TA Performance cover on it and can drain it out, but doesn’t the oil require an additive, a friction modifier?

Thanks for any info on how much of each to use, and what kind. I know Ford changed the specs on the gear oil a bit after I got the car.

I think I’ll have to rig up some kind of hose to get the thing topped off without making too much of a mess.


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[RubberCtyRauder]

you fill it til it runs out the fill plug on the front side of differential housing. you do not top off, over filling will likely cause a axle seal to leak and blow excess out vent. shoukd be done with car level

[fastblackmerc]

Follow recommendation in owners manual.

I recommend synthetic fluid. Ford changed recommended weight to 70w140.

[Svashtar]

Follow recommendation in owners manual.

I recommend synthetic fluid. Ford changed recommended weight to 70w140.


Thanks to you both; I’ll check the invoice from my mechanic back then as I think there was more than just the fluid. It may be an all in one you can buy now.


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[Svashtar]

you fill it til it runs out the fill plug on the front side of differential housing. you do not top off, over filling will likely cause a axle seal to leak and blow excess out vent. shoukd be done with car level


Got it, thanks. I believe my access plug is on the top right of the TA cover, so it’s possible to overfill by leaving the front fill plug on I take it?

I’ll check the manual for recommended service schedule. It’s been 6 years, but not a huge amount of miles.

[RF Overlord]

According to Ford, axles filled with synthetic fluid do not require the fluid to be changed. Since the Marauder came with conventional fluid, once you change it over it shouldn't need doing again unless contaminated.

Many fluids, like Valvoline, Mobil 1, Royal Purple, already contain the required friction modifier. Motorcraft fluid does not, so you'll need an bottle of XL-3.


I believe my access plug is on the top right of the TA cover, so it’s possible to overfill by leaving the front fill plug on I take it?I have the T/A Performance cover, too, and I read somewhere not to use their fill plug(s), only the drain plug, and to fill it by the plug on the axle itself.

[sailsmen]

I change mine when I take the cover off to inspect, which is every 2-3 years.

[Svashtar]

According to Ford, axles filled with synthetic fluid do not require the fluid to be changed. Since the Marauder came with conventional fluid, once you change it over it shouldn't need doing again unless contaminated.

Many fluids, like Valvoline, Mobil 1, Royal Purple, already contain the required friction modifier. Motorcraft fluid does not, so you'll need an bottle of XL-3.


Thanks for the info Bob. I wasn’t aware those brands added it in, but that makes sense.

I checked the old invoice and it was Motorcraft fluid with a separate line item for friction modifier. I won’t worry about it then.


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[justbob]

According to Ford, axles filled with synthetic fluid do not require the fluid to be changed. Since the Marauder came with conventional fluid, once you change it over it shouldn't need doing again unless contaminated.

Many fluids, like Valvoline, Mobil 1, Royal Purple, already contain the required friction modifier. Motorcraft fluid does not, so you'll need an bottle of XL-3.

I have the T/A Performance cover, too, and I read somewhere not to use their fill plug(s), only the drain plug, and to fill it with the plug on the axle itself.



Mobil1 will chatter like you filled it with motor oil. Been there!


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[fastblackmerc]

Mobil1 will chatter like you filled it with motor oil. Been there!


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Redline won't.... been there too!

[tbone]

As far as changing, my carbon clutches started to moan a little around corners after only 5000 miles. Changed the oil and all is good again. I put in Royal Purple and friction modifier as well even though it may not be necessary. It can't hurt.

[tbone]

I think I’ll have to rig up some kind of hose to get the thing topped off without making too much of a mess.


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This the marine version but you get the idea.

[Red Rum]

Royal Purple sells there gear oil with the friction modifier already in it. I did mine last Summer works flawlessly.

[Svashtar]

This the marine version but you get the idea.


Yes, that would be handy anyway, thanks!

The reason the subject came up is I thought I heard a drone from back there yesterday, while driving at constant speed, so it got me thinking. But last night it was quiet. Unless I start hearing noises I’ll assume the fluid is Ok and doing its job.


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[Turbov6Bryan]

Just my logic here
Ford says 10,000 mile oil change interval and 100,000 mile trans service on my 5.0 mustang. Seems a little extreme eh?

On the mm rear end, it depends on how many miles are on it, and how many miles you put on it

I did my car at 169,000 miles it was pretty dirty, so I brake cleaned it as best as possible 2-3 cans and 1.5 years later it was stinky and not as dirty at 175,000 miles
Valvoline full synthetic 70/140

So I changed it again. Same process.

Generally speaking, if you drain it out and it's as clean as the stuff your putting in there, then you can extend the interval.

Just like your engine, if you change the oil, and the new oil turns black after a day or two, you probably should change ( or should have been) more often

If your car has 59,000 miles and you put 100 miles per year, you'll probably be dead by the time it's due for a change