Changing CX-9 transfer case gear oil (photos)


2013 CX-9 Touring
here's a quick write up on how I changed the CX-9 (AWD models only) transfer case 75W140 gear oil,

Step 1.

need to get some front ground clearance to get under the SUV, so I got some 4" thick solid cement blocks (they run about $1.44 each per block) from Home Depot or Lowe's and rolled both the front wheels up using the 2" high red bricks as a helper to get the wheels up the 4" thick blocks. I then chocked the rear tires just as a safety precaution in case the truck rolls back (highly unlikely but can never be too safe).

*note: you must use the 2" red bricks to help get up the 4" cement blocks otherwise the truck gets stuck and just pushes the cement blocks. You may also do the same setup for the rears to be absolutely level front and back but I felt it was unnecessary since it was just a slight 4" rise up front.

I find it easier and safer to just roll up the blocks then jack up the car on one side.
also it keeps the car level on both sides at the same time and the 4 inch rise provides just enough clearance to get under the CX-9 without too much incline, since we need to fill the transfer case and it needs to be as level as possible w/o too much incline.

SAVING $1.83 is not worth your sight !!

Step 2.

need to locate the transfer case fill plug (it's the one with a 3/8" square drive cavity and orange thread sealing compound)

a led light with a magnetic base will help, it's very dark down there

the transfer case is located underneath approximately between the driver and passenger seats, it is near the engine oil drain plug,

follow the U pipe you see in the photos below and you'll be able to see it ,
you'll need a short stubby ratcheting 3/8" socket driver (make sure it is the low profile type);
the head of the 3/8" drive can just barely fit ! there is a metal plate on the opposite side of the 3/8" drive
we got lucky, if any more tighter, we wouldn't be able to get the plug out due to the stack up tolerance
of the loosened plug + ratchet head.

there's a stupid black cross beam right under the plug, so I had to access the plug from the left side of the beam and cross over to get to the plug with my stubby ratchet, it is hard to explain, you'll understand when you see for yourself.

here are some pictures of the transfer case plug removed, note the black gear oil and sludge,

see here for Ford Edge/Flex AWD problems (they use the same exact transfer case as the CX-9):

my CX-9 AWD only has 38,000 miles mostly highway miles (I cannot believe Mazda calls this lifetime oil) Based on some investigation from the Ford Edge forum, the Ford Edge uses the same exact transfer case and the OEM oil is Motorcraft brand 75W140 gear oil and new oil color is suppose to be an amber yellow color which indicates to me my oil is beginning to break down since it's dark and black.

Step 3.

need to suction out as much as the old oil as possible

you'll need a suction gun, the gun comes with a short 1/2" OD PVC tube. I found this to be too short and too rigid to get it thru the transfer case hole, so I bought a longer more flexible 3/8" OD PVC tube, I had a heck of a time getting that smaller 3/8" tube on the suction gun barb connector but trust me it will fit just need to force it on, the longer tube definitely helps when you're under the car and the smaller OD allowed me to snake the tube deeper into the transfer case hole.

I experienced the same thing as some fellow members reported, it seems the tube hits an obstacle and cannot get all the way into the transfer case, you'll probably get in maybe an inch and a half before you can't go any further, I then started to suction the old oil, got about maybe 1/2 of a cup before the suction gun was just sucking nothing but air.

this is a picture of the 3/8" OD PVC suction tube in the transfer case sucking out the old gear oil

here's a video of the old oil in the suction gun , notice how thick and black the transfer case oil is only after 38,000 miles, the smell is absolutely acrid :

****************************************************************************************************************************************************************************************************************May 2, 2015 update***

I switched to an electric sunction pump which makes the job a lot easier and cleaner,
see link:


Step 4.

after you suction out as much of the old oil as possible, you need to refill with new 75W140 gear oil,

this is straight out of the CX-9 owner's manual, I cannot believe the gear oil capacity is only 1/2 a quart,
that's way too little for this size SUV and transfer case, no wonder we're having so many transfer case issues and burning oil smell, the gear oil is breaking down over time until it no longer lubricates the transfer case gears and the transfer case literally burns itself out

you need to buy a pump with a 3/8" PVC tube to get the new oil into the transfer case

Step 5.

keep pumping the new oil into the hole and try to flush out as much of the old oil as possible, once the oil that is coming out of the hole becomes clear or lighter , you can stop pumping and wait for the oil to stop dripping,

Wipe clean the plug threads and thoroughly wipe clean any excess oil that dripped down on to other components (otherwise the smell will permeate into the passenger cabin).

Reinstall the plug and you're done.

You can use a torque wrench if you want, it'll have to be stubby wrench though, the space is very tight, sorry I don't know the exact inch-lb torque specified, I just made sure it was tight, you don't want to over torque it though, the transfer case is casted metal and will crack if you over do it, so be careful.

Also, you can add more orange thread sealing compound, just a little if the original got stripped.
I didn't need to since my original OEM orange seal stayed on and it's suppose to be reusable guaranteed
to 5 times.

But just in case, this is what you need in case yours get stripped, it's made in the USA by ND Industries
Vibra-TITE VC-3 Threadmate. It's much better than Loctite or white liquid teflon for vibration and sealing. You spread it into the threads and let it dry and it dries to a rubbery coating that seals and keeps the plug from coming loose. And oil on the mating threads does not inhibit performance.

Final thoughts...

I have driven 1500 miles since this transfer case change and happy to report everything is smooth as silk, it definitely seems the vehicle drives smoother during the gear shifts and no burnt oil smell.

Since the process is so easy, I decided to do the procedure again and take a look at the oil condition this weekend, below are a picture of the plug and oil after 1500 miles. The oil is definitely less viscous than before, it flows way smoother. The color is still black, probably from the leftover black oil that the suction gun couldn't reach but I'm sure after two more changes the black color will be eliminated.

I recommend doing this maintenance every 20,000 miles or less, I myself is leaning towards the latter maybe even every 6000 miles when I change the engine oil might as well change the transfer case oil as well.

The oil capacity in the transfer case is just not enough for it's size. Because of the low capacity, the oil breaks down quickly causing the burnt oil smell and eventually transfer case failure.

From a technical view, I submit it's not how hard the car is driven but rather there are two factors to consider when dealing with this low capacity,

1) length of continuous driving

this is just my theory, but if the oil has indeed broken down and driving the car for more than say 3 hours continuously, I believe there will be overheating issues

2) cold weather, when it's cold, the oil is pretty thick and can't lubricate the gears enough

Maybe some owners who had their transfer case replaced can chime in and help us out, is your daily commute a long drive and do you live in a cold part of the country ? and at what mileage did you encounter transfer case issues ?

Personally, I would consider changing the oil before a long road trip with the family just to make sure the transfer case doesn't overheat AND changing the oil right before the cold winter season every year.

A good analogy would be like never changing the engine oil, who would ever try to run an engine 100,000 miles without changing the oil:

Same thing here, gears in the transfer case are running all the time and Mazda expects the oil to last 100,000 miles, I think not.

*note: some dealerships who are willing to do this transfer case oil change service will charge ~$159
most dealerships won't even try and will say it's a sealed unit and cannot be done, blah, blah, blah .....yeah right

Finally, I suggest a transmission fluid change every 30,000 miles
and rear differential fluid change every 30,000 miles.

I'm pretty sure I can get at least 150,000 trouble free miles with this maintenance plan, *knock on wood*
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2013 CX-9 Touring
thanks for compliment Scott, I hope it helps out fellow AWD owners.

for AWD and FWD CX-9, does anyone know if there is such a thing as a front differential

and if so, does the oil need to be changed ?

I know the rear differential needs to be changed
2012 Mazda CX-9 Grand Touring AWD
Thanks for the info. Our 2012 just hit 30,000 miles. I changed out the rear differential oil a few weeks back. I think I will also need to do this soon. I doubt our local dealers will do it as 90+% are FWDs in this area. I am so curious if the "new revised ones" have more oil in the case. Mazda really should be changing all of these out, but I guess they want to take their chances and save money. Clearly a very bad design.


Potential Scammer!
Great thread. This should help out alot of members to do the job themselves.

I had my transfer case recently replaced with the updated newer unit. So wont have to worry about doing a fluid change anytime soon. But i plan on doing like the OP and swapping out the fluid every 20K or so just to be safe.


2013 CX-9 Touring
Thanks for posting, incredible there is no drain plug.
You're welcome, agreed, it's crazy there is no drain plug, I do recall a fellow member actually drilled and tapped in a drain plug himself. That's actually the correct way to do this but that's way above my mechanical capabilities and I'll probably screw it up and crack the transfer case. I'll just rely on the suction gun and flush method for now.
2012 Mazda CX-9 Touring AWD
Looks like it wouldn't be much fun to do while the car was hot but when dealing with heavy gear oils like this you're much better off trying to remove them warm. The exhaust pipes will cool down much faster than the transfer case so I'd suggest driving it to get everything up to temp then waiting just long enough that you're not burning yourself on the exhaust before trying to suction the fluid out.

With the capacity being so small I'd also suggest siphoning out what you can, refilling, then repeating the process until you get pretty clean fluid coming out.

My only question is about the original Mazda spec fluid and if it had a friction modifier included. That's an additive for gear out designed to make the limited slip differential discs operate smoothly and prevent chatter. I'm not sure if it's needed or even advised to run it in a transfer case. The royal purple you used has the friction modifier in it. A lot of Ford fluids do not com with the modifier and it has to be added separately if required. This is the stuff, I had to add it back when I had an Expedition and was changing the rear diff fluid:


6 wagon for life
2014 Mazda CX-9 AWD GT w/ Tech Package
Great write up avidien! With all the TC talk lately it's nice to see someone tackle this and take photos along the way. Of note: I thought the quantity of the oil was pretty important, but you said you just filled back until the level with the fill plug... Is this appropriate? Or should we worry about replacing exactly what was sucked out? I like the idea of flushing it better than direct swapping, due to lack of drain plug, but was just curious on your thoughts.
06 speed6 GT/08 CX-9 GT
When I do the fluid changes in the speed6 for tc, rear diff and tranny I always fill until a little spills out of the fill plug and it's right about the amount it needs. It should hold true for the cx9 as well.
2012 Mazda CX-9 Touring AWD
Any diff, transfer case or transmission I've ever worked on with a fill plug was fill until it started coming out of the hole with the vehicle level.


2013 CX-9 Touring
Great write up avidien! With all the TC talk lately it's nice to see someone tackle this and take photos along the way. Of note: I thought the quantity of the oil was pretty important, but you said you just filled back until the level with the fill plug... Is this appropriate? Or should we worry about replacing exactly what was sucked out? I like the idea of flushing it better than direct swapping, due to lack of drain plug, but was just curious on your thoughts.
hi Voldsom,

this was my mindset and plan when I started " measure exact amount taken out and put back exact amount"

but trust me when you're down there and sucking up all that thick oil, it's almost nearly impossible to measure the exact amount taken out, most of the old oil gets stuck in the suction gun.

If you go to youtube and search "transfer case oil change" , you will see that for all vehicles,
the videos show filling the transfer case until you see the oil dripping out ,
the fill hole location is the location the oil should be filled to.

Robertof is correct:
"When I do the fluid changes in the speed6 for tc, rear diff and tranny I always fill until a little spills out of the fill plug and it's right about the amount it needs. It should hold true for the cx9 as well. "

Also, it's a good way to flush out the bad oil, since there is no drain plug.
BTW, I've driven over 150 miles since the oil swap and no issues so far or burnt oil smell.

Looks like this is the way to go to solve the transfer case issue.

I refuse to be a sheep to Mazda corporate greed, they know full well there's a transfer case issue (that's why they sent out warranty letters to extend transfer case to 7 years/90,000 to cover there behinds instead of issuing a full blown recall) but won't step up the to plate which is pretty surprising since all the other manufacturers have been recently severely fined for ignoring known safety issues.
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6 wagon for life
2014 Mazda CX-9 AWD GT w/ Tech Package
Thanks for the followup avidien. Your logic holds true from my limited experience as well. I suppose that's why they call it a "fill hole" when they throw it on the side... makes it dummy proof for the quantity needed :) Also makes flushing it logical as well, to try and get some of that crap out. May cost a little more in material (more good gear oil wasted), but worth it to "do it right".
That video of the old oil in your suction gun makes it pretty obvious what to expect, a freakin' mess... That stuff looks disgusting, and the fact that everyone reports a god-awful smell makes it even worse
2011 CX-9 GT FWD RES
Hi All,
new here; Does this only apply to the AWD version? I have an 2011 grand touring with 44k miles, I've done synthetic oil changes every 7k+ via local mechanic, but would like to address some of the other longer interval fluids maintenance.

I'm still catching up on multiple threads on Transfer case, but I just realized maybe FWD don't have transfer case? Assuming transfer case is for distributing power to read drive shaft on AWD?

This was still a great write up with pic's and recommended tools, thanks very much.

2012 Mazda CX-9 Grand Touring AWD
Tried this today with the OTC suction gun; the original method avidien used. I just don't feel like I got enough of the old gear oil out as it is just so little oil in it, but filled as avidien did and kept filling until some of it starting coming out and did a little bit longer. The location of the plug is a pain with the exhaust and other things in the way. We have 33,000 miles on out 2012. Next time I will also try the electric suction pump unless avidien comes up with another great idea before then (cool)

I wonder what process the dealers use that charge the $159 to do this? I know the ideal way to do this is to remove the PTU and put it on its side and get the oil out, but that definitely does not look like an even remotely fun job to do.

I can't wait to hear other processes.