'17 Grand Touring AWD, around 70K. Couple of weeks ago noticed a oil drip on garage floor towards left rear. Finally got it up on the lift. Left side seal where axle exists the diff leaking. Excessive shaft play up and down!

YAY!

Not a clogged vent, more likely right rear brake had a slight drag from a errant EPB while the left wheel spins easily.

I will be changing it myself as I'm retired and have a lift and tons of tools.

The painful part is extended warrant expired 12/22/25 AND she nixed my suggestion she trade it in last month as we live in a high salt area.

Pete

 

Are these differentials vented? Haven’t got under mine to look yet. But have seen vents clog before and blow out seals.

 

OG, I do believe there is one as I saw a vent tube mentioned when i was look at diff diagram. This hasnt been leaking long as wife parks in the middle bay of my fairly new cement floor garage.
But this seal is blow out due to a blown bearing on the left side of the diff. There is tons of play in the shaft where it enters the diff. Took a few oz's of diff oil to top it off so it wasn't empty. Researching possibly causes are different tire sizes left to right. Electronic parking break hanging up on either side causes pressure/wear on the slide bearing in the diff. I'm tempted to disassemble the diff and change the bearing but wife needs here beloved SUV for work.
Today i checked rear wheels rolling resistance. Left one rolls a lot more freely then the right one. I did rotors and pads on this CX-5 early last summer and did have a issue with he damn EPB procedure post install. I had to run the procedure a few time to finally get it done. At that time both wheels spun freely.
But we live in Maine and its been even for here exceptionally cold and snowy. there is a thick layer of dried road salt under the car.
I've been wrenching car for 50 years. Personally i avoid automatics, and AWD as in my experience they tend to fail more often and are expensive to fix.
Not looking forward to swapping in a new diff. Obviously will have to address what I can assume is some right side brake drag.

Pulled the driveshaft yesterday so I can at least move the CX-5 around. The Mazda dealers by me aren't very nice and seem to dislike customers like me that do our own repairs.

Pete

 

Its located on the top of the differential case
Unless you submerged the Mazda in muddy water they generally seldom ever get clogged up.

 

Hmm drove it today with the RedNeck repair. Front to rear drive shaft pulled. seems fine that way like a few people said it would.
Still researching buying a brand new full differential.

Pete

 

A new OEM rear differential will be over $3k if I'm not mistaken. Used would be slightly cheaper, but it depends on what you find.

 

China made ones are about $1000 and are the complete assembly.
Mazda online sites are vague and all over the place price wise.
At this rate I am going to dissemble it myself and see if i can change the bearing and the seal ! See it listed for $52.
flush the damn thing with clean fluid a few times and trade it in for a Rav4.

Pete . This is why I ave avoid AWD and Automatics my 50 years of auto ownership.
(my CO-dailys are a '17 Mazda3 GT 6peed and a '15 Prius V)

 

From Mazda Wholesale direct .
$ 2366.64 Differential Assembly - Mazda (KAT227020) (Coupler not included)

$ 831.66 Differential - Mazda (KA0327100B) Thinking Im going to try just doing the diff with my existing coupler.

LOL , I just went thru and deleted the complete assembly from my cart, proceeded to payment screen.
Calculates my shipping as $1290! WTH?
msg'd support for correction of ship charges.

 

You may try and ask if they will give you a discount based on who your auto insurance carrier is?
Or use the senior or military discount question

All they can say is NO

 

Shipping amount from another online dealer is like $55. differential about $75 then MazdaDirect.

Pete