2017~2025 CX-5 Rear Differential Failure

[AL Cx5]

not bad to do at 30k-its pricey but only takes a quart to do job...i used a jack/stands and it took an hour-parts guy asked why i need to buy 4 quarts-said i have owned honda/acura they always had me chasing my tail to get more fluid,and i may do it at 15k just cause i can

Darn Mazda diff and transfer case fluid is $30. Takes 1 quart to do both.

STILL $30 vs being down and the cost to replace. I'll change mine...

 

[sm1ke]

Just a note - new SG1 fluid isn't clear out of the bottle. It's like honey.. very close to this colour:

When I drained the fluid out of my CX-9 at 70k kms, it looked like brand new engine oil. Darker than the brand new fluid, but not bad by any means.

 

[AL Cx5]

Just a note - new SG1 fluid isn't clear out of the bottle. It's like honey.. very close to this colour:

View attachment 379774

When I drained the fluid out of my CX-9 at 70k kms, it looked like brand new engine oil. Darker than the brand new fluid, but not bad by any means.

Thanks for clarifying the color!

For me, change in color indicates contamination. We can debate if this is enough to damage the gear boxes or send in a sample and have it analyzed and know.

I'll send a diff sample on our CX 5 at 30k and report back. We were in a time crunch to change the fluids on my friends 2nd Gen CX 5. So no sample collected.

I've seen contaminated fluid, diff, power steering and hydroboost wear out seals and the shafts. So bad that we changed out the P steering pump, hydraboost and diff pinion. Bearings were running ruff in the P steering pump. The shafts had grooves where the lip seals "seal".

 

[cz5gt]

When inspected, the differential or PTO oil is dark or black. During production, differential ring and pinion gears receive a manganese phosphate coating (commonly referred to as black oxide).

This coating forms a porous, oil-retentive surface that improves boundary lubrication and reduces adhesive wear during initial contact cycles. Designed as a sacrificial layer, it is gradually removed under load throughout the break-in process.

As a result, after the first few hundred miles, or at the initial gear oil service interval, the lubricant may appear darkened by the worn-off coating. It will contain trace ferrous particles from the normal run-in of the gear teeth and bearing surfaces

 

[AL Cx5]

When inspected, the differential or PTO oil is dark or black. During production, differential ring and pinion gears receive a manganese phosphate coating (commonly referred to as black oxide).

This coating forms a porous, oil-retentive surface that improves boundary lubrication and reduces adhesive wear during initial contact cycles. Designed as a sacrificial layer, it is gradually removed under load throughout the break-in process.

As a result, after the first few hundred miles, or at the initial gear oil service interval, the lubricant may appear darkened by the worn-off coating. It will contain trace ferrous particles from the normal run-in of the gear teeth and bearing surfaces

Excellent point. I didn't notice the fluid on the 2021 2500 series truck being dark. Maybe they didn't coat the gears with manganese phosphate.

On our drag race diffs, we don't coat the gears. Also, no break in procedure other than spinning the rear wheel on jack stands and listening and feeling for vibration.

Here is a thread from Bob is the Oil Guy. After reading this, I'll change the fluids at 20K, then on 30k intervals. $30.00 and an hours work may prevent costly repairs down the road. I'll put some of the fluids in a clear container and take pictures. Maybe send them off to be analyzed.

https://bobistheoilguy.com/forums/threads/phosphorous-coating-on-differentials.120944/

Manganese Phosphate Coatings | Calico Coatings

 

[cz5gt]

Yes. My post is specifically for the CX5.
Its nice that Mazda does that. I dont know wheter other car makers do it.

 

[AL Cx5]

Yes. My post is specifically for the CX5.
Its nice that Mazda does that. I dont know wheter other car makers do it.

X2, AGAIN Mazda goes an extra step to produce the best product at a competitive price point.

It's a quirky car for sure, in a good kind of way! As an example the procedures for putting the rear brakes in maintenance mod and resetting the trans adaptive is interesting..WEEE

 

[nickswhip24]

Darn Mazda diff and transfer case fluid is $30. Takes 1 quart to do both.

STILL $30 vs being down and the cost to replace. I'll change mine...

i think i paid $40 or$ 45 per quart

 

[cz5gt]

yes 35 is the msrp without local tax in US.
If you bought from your local dealer and the end user price was more than 35 (without tax) they are inflating the price retail.

 

[AL Cx5]

i think i paid $40 or$ 45 per quart

Well then, maybe I'll wait and do it at 40 or 45K intervals.

 

[BoomerZoomr]

When I purchase a brand new automobile, I always change the engine oil at the first 1000 mile mark. While doing that, I also had the dealership verify that my 2025 CX5 transfer case and rear differential were full of oil… which they were. The service guy informed me they would charge me extra ($39.99) to check those two gearbox levels. Seems like once upon a time checking all fluid levels was included with the oil change… he did have to remove the plastic cover to access the transfer case. I just wanted to verify the levels were good, after reading about folks having low levels from the factory.

 

[AL Cx5]

When I purchase a brand new automobile, I always change the engine oil at the first 1000 mile mark. While doing that, I also had the dealership verify that my 2025 CX5 transfer case and rear differential were full of oil… which they were. The service guy informed me they would charge me extra ($39.99) to check those two gearbox levels. Seems like once upon a time checking all fluid levels was included with the oil change… he did have to remove the plastic cover to access the transfer case. I just wanted to verify the levels were good, after reading about folks having low levels from the factory.

I sure hope the guy REALLY checked your gear boxes! Rear is a snap to check. I've taken the front belly pan off so many times, it's a five minute job, max. I LIKE that belly pan, keeps the engine clean and helps aero.

Even though Mazda has made it difficult to service the gear boxes, requiring a 24mm box wrench, it's a very simple job. to drain and pump in new fluid.

I have been working on my friends 2021 CX 5 with him. I keep finding stuff that the techs messed up or overlooked. First was they didn't replace the oil plug/filter access panel. Next they replaced only one rear disk but not the other. The sensor in the oil pan was leaking oil, the screws were loose from when the engine was removed to fix and oil leak. Someone over tightened both front brake bleeder screws. I'm sure I've forgotten a few more.

Oddly, both of his gear boxes were at the correct level. We changed the fluids at 70k mi just the same.

I find stuff incorrectly installed or serviced. I check behind folks if I let them do some work for me.

 

[BoomerZoomr]

I sure hope the guy REALLY checked your gear boxes! Rear is a snap to check. I've taken the front belly pan off so many times, it's a five minute job, max. I LIKE that belly pan, keeps the engine clean and helps aero.

Even though Mazda has made it difficult to service the gear boxes, requiring a 24mm box wrench, it's a very simple job. to drain and pump in new fluid.

I have been working on my friends 2021 CX 5 with him. I keep finding stuff that the techs messed up or overlooked. First was they didn't replace the oil plug/filter access panel. Next they replaced on rear disk but not the other. The sensor in the oil pan was leaking oil, the screws were loose from when the engine was removed to fix and oil leak. Someone over tightened both front brake bleeder screws. I'm sure I've forgotten a few more.

Oddly, both of his gear boxes were at the correct level. We changed the fluids at 70k mi just the same.

I find stuff incorrectly installed or serviced. I check behind folks if I let them do some work for me.

The dealership provides a short video of the underbelly inspection… it looked legit and he had the large plastic cover removed. I think the gaskets under the fill/drain plugs are supposed to be replaced when removed… now whether he did that, who knows. The guy working on my car sounded like (in the video) a grown man from the country, which was encouraging. Getting good mechanics to do this type of routine work must be challenging for the shops. I started working on cars as a teenager… today I imagine most of them don’t leave their video game consoles. Always good to double check work done by someone else.