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