Rear Differential Fluid (AWD) vs. PTU Fluid (AWD)

[Isaac Shea]

Aloha guys,

So I'm looking for a mechanic to change the differential fluids in my 2015 SHO, but I'm a little confused about the specifications. There's Rear Differential Fluid, which asks for (2.4) pints of 80W-90 Premium Rear Axle Lubricant, and there's also PTU fluid which asks for (180z.) 75W-140 Synthetic Rear Axle Lubricant. So which fluid goes where when they both say "Rear" ? I'd like to find a mechanic I can translate your wisdom to as Ford service in Hawaii wants to charge me $500...I told them for an oil change you can go to ****.

Thank you!

 

[Shokev]

Aloha guys,

So I'm looking for a mechanic to change the differential fluids in my 2015 SHO, but I'm a little confused about the specifications. There's Rear Differential Fluid, which asks for (2.4) pints of 80W-90 Premium Rear Axle Lubricant, and there's also PTU fluid which asks for (180z.) 75W-140 Synthetic Rear Axle Lubricant. So which fluid goes where when they both say "Rear" ? I'd like to find a mechanic I can translate your wisdom to as Ford service in Hawaii wants to charge me $500...I told them for an oil change you can go to ****.

Thank you!

The 75w goes in the ptu


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[Isaac Shea]

Thank you! And that's the smaller box in the rear. So the 80W goes in the front? They should put something in the manual for ignoramus like myself..

 

[Shokev]

Thank you! And that's the smaller box in the rear. So the 80W goes in the front? They should put something in the manual for ignoramus like myself..

https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2299935&page=all


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[SHOdded]

It IS stated in the owners manual what goes where. But it IS also confusing when they call it REAR axle lubricant, but that is due to what the fluid was originally developed for and the dominance of RWD at the time. A lot of nomenclature comes from what was in use a century or more ago.

 

[SM105K]

I would just buy some Redline Lightweight Shock Proof fluid and put it in both. Super easy, barely an inconvenience.

 

[Shokev]

I would just buy some Redline Lightweight Shock Proof fluid and put it in both. Super easy, barely an inconvenience.

Is that what you are running


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[SM105K]

Is that what you are running


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That is what I am running. Actually there are quite a bit of us now, and everyone says the same thing. The car rolls so much smoother now.

 

[jman1200]

And that's the smaller box in the rear. So the 80W goes in the front? They should put something in the manual for ignoramus like myself..

No.
The PTU (power transfer unit) is the one located in between the front axles (right under your feet) and uses the 75-140.
The RDU (rear differential unit), located in between the rear axles uses the 80-90.

 

[ShogunofHarlem]

Aloha guys,

So I'm looking for a mechanic to change the differential fluids in my 2015 SHO, but I'm a little confused about the specifications. There's Rear Differential Fluid, which asks for (2.4) pints of 80W-90 Premium Rear Axle Lubricant, and there's also PTU fluid which asks for (180z.) 75W-140 Synthetic Rear Axle Lubricant. So which fluid goes where when they both say "Rear" ? I'd like to find a mechanic I can translate your wisdom to as Ford service in Hawaii wants to charge me $500...I told them for an oil change you can go to ****.

Thank you!

My local dealer just charged me $67.00 for ptu fluid change. Differential was around 150 if I recall correctly.

 

[jman1200]

That's cheap. I paid more than $40 just for the PTU oil.

 

[Joshw0000]

The PTU is in the front (75w-140 - 1 quart) and the RDU is in the back (75w-90 - a little more than a quart). I put Royal Purple in mine but Redline and Amsoil both have great reviews.

If you line up your front tires perfectly and shine a light through, you can see the plug for the PTU through your front right rim. That's how I got to mine, with several socket extensions.

And the RDU is a little easier to access in the back with a low profile socket.

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[Isaac Shea]

The PTU is in the front (75w-140 - 1 quart) and the RDU is in the back (75w-90 - a little more than a quart). I put Royal Purple in mine but Redline and Amsoil both have great reviews.

If you line up your front tires perfectly and shine a light through, you can see the plug for the PTU through your front right rim. That's how I got to mine, with several socket extensions.

And the RDU is a little easier to access in the back with a low profile socket.

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The transmission guy I went to siphoned out and replaced with 1 quart 75w-140 Royal Purple in the back RDU. I hope the 80w-90 can go in the front PTU... Thoughts?

 

[Shokev]

The transmission guy I went to siphoned out and replaced with 1 quart 75w-140 Royal Purple in the back RDU. I hope the 80w-90 can go in the front PTU... Thoughts?

75w goes in the front


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[Joshw0000]

The transmission guy I went to siphoned out and replaced with 1 quart 75w-140 Royal Purple in the back RDU. I hope the 80w-90 can go in the front PTU... Thoughts?

I wouldn't drive it much until you (or someone) can siphon the RDU and put the correct weight back in it. And I definitely wouldn't put lighter weight in the front. The PTU is surrounded by heat. 90 weight wouldn't protect it very well once things heat up.

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[Isaac Shea]

I wouldn't drive it much until you (or someone) can siphon the RDU and put the correct weight back in it. And I definitely wouldn't put lighter weight in the front. The PTU is surrounded by heat. 90 weight wouldn't protect it very well once things heat up.

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[Isaac Shea]

Okay, and thank you again for the information. I have not yet replaced the PTU (front) fluid. My manual only asks for (.56) quarts of 75w-140. It seems the front should take more, but I'll roll with the factory specs.

As mentioned previously, I currently have 1 quart 75w-140 in the back RDU. My manual asks for 1.15 litres (or 1.21 quarts) so I could probably add .21 quarts extra to meet factory specs.

I'm slowly seeing why this oil change costs $500 at Ford...

 

[Joshw0000]

If you decide to do it yourself, you can save some money and sleep better knowing it's done right. I did mine last month.

https://r.tapatalk.com/shareLink/to...share_fid=156498&share_type=t&link_source=app

Everyone here is incredibly helpful. If you decide to tackle it, I'll give you some pro tips from a non-mechanic that'll save you some time and headache. I.e. cheap tools I own now that I should have owned before I started.

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[Joshw0000]

Also note that a lot of Ford dealerships won't change the fluids at all, since they're supposedly "lifetime fluids". Or at least Ford thought so at first. That's why most of us don't have drain plugs.

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[Isaac Shea]

Also note that a lot of Ford dealerships won't change the fluids at all, since they're supposedly "lifetime fluids". Or at least Ford thought so at first. That's why most of us don't have drain plugs.

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Thank you so much for all the great information. I hate wasting the Royal Purple 75w-140 already in the RDU, but I guess I should stick to factory specs with the 80w-90. I'll go ahead and replace the PTU with the 75w-140...

Mahalo!