Gear Oil Weight?

[Rearanger]

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I have some Valvoline 75w-90 full synthetic gear oil with slip aditive. Manual calls for 80w-90 in differential, but lots of talk about the 75w-90 being perfectly OK. I have 7.5 gears.

Any knowledgeable advise?

Thanks

 

[fastpakr]

100% fine to use either one.

 

[cbxer55]

Because of my 04 Lightning, all I keep in my garage is Ford full synthetic 75-140. I use that in all my vehicles and my one shaft driven motorcycle.

 

[Rearanger]

100% fine to use either one.

That's what I'm thinking. Got 4 qrts of the oil for free, don't want to waste it.

 

[Uncle Gump]

I didn't see where this post had anything to do with a 3.0L... so I moved it to the axle forum. Just trying to keep things organized.

Keeping topics in the correct forums also provides better search results...

Carry on...

 

[Eddo Rogue]

Even gear oil has come a long way. I've use both, depending what's available, in multiple applications....never had a problem. I typically go with lighter stuff in anything new-ish, and heavier stuff in anything that's well broken in.

 

[Dirtman]

75w90 is simply synthetic 80w90. Any Ford diff that originally called for 80w90 can use either 80w90, 75w90, or 75w140.

75w90 and 75w140 already have friction modifiers for limited slip differentials, 80w90 does not so keep that in mind if you have limited slip.

Ford puts 75w140 in all trucks now, even if you take a old 85 ranger to a dealer they will squirt it full of 75w140. So like @cbxer55 I don't bother buying anything but 75w140 anymore.

 

[stx4.0]

Personally I always leave the friction modifiers out! All it does it quiet the rear axle and allow slippage on the clutch plates and in other words wear them out faster,even the carbon fiber clutches.They bite harder and last longer when you leave it out so I dont mind if the rear axle has some whine to it.I used to rebuild my Explorers clutch pack about every 70k miles but a guy at ford told me one time if you want it to last a little while then leave that modifier out.Some of the best info I have gotten in awhile because they go way past 100k miles before losing there bite with straight axle lube.

 

[19Walt93]

75w140 isn't thicker than 80w90, it gets no thicker than a 75 weight when it's cold and no thinner than a 140 weight when hot. There is no such thing as multi-viscosity oil or fluids- the viscosity is more stable with temp change. I'd use the 75w90 in a minute, too. I also use friction modifier in every limited slip rear I build to prevent chattering on corners and noise.

 

[sgtsandman]

Last axle gear oil change, I went with 75W-90 front and rear. I’ve done time changes on mine since I don’t hit the mileage their maintenance schedules recommend. The rear was a bit gray the last time I change it and the front, the same with this change after off roading (81,500 miles - I think). The 2011 is 10 years old this year and I used the oldest schedule they list to do the preventative maintenance (I’m pretty sure that is 120,000 miles).

Do not stick to the OEM recommended mileage. I would go no longer than 60,000 miles on the rear axle and 90,000 miles on the front. Synthetic or petroleum oil is your preference. Synthetic stinks less.

Also, the synthetic being “for the life of the vehicle” is a load of garbage. If you swap vehicles every 10 years or less, maybe. If you keep them for decades, you are begging for a failed axle.

Ask the Dodge and Jeep guys how hard it is to find an axle for their vehicles. All because the gear oil change intervals are ignored or too long.