Does Transmission Fluid & Differential Fluid have a time limit

[raaizin]

Porsche recommends trans and Diff fluids based on time as well as miles. Is there any reason for this as it seems unnecessary as there isn't combustion going on to contaminate the fluids? Shouldn't it be just based on miles?

 

[Propflux01]

Same reasons as time on motor oil. Moisture over time.

 

[kschachn]

Same reasons as time on motor oil. Moisture over time.

On the other hand very little water gets into ATF as compared to motor oil, inside an engine there is a relatively huge about of water from the products of combustion as compared to a transmission. Add to that any mixed sulfur oxides and this is what deteriorates the TBN of the engine oil.

 

[raaizin]

On the other hand very little water gets into ATF as compared to motor oil, inside an engine there is a relatively huge about of water from the products of combustion as compared to a transmission. Add to that any mixed sulfur oxides and this is what deteriorates the TBN of the engine oil.

That was what I was thinking

 

[SwampSurvivor]

There's plenty of 250,000 mile vehicles in the junkyard on the original differential fluid ...

 

[Propflux01]

There's plenty of 250,000 mile vehicles in the junkyard on the original differential fluid ...

The OP asked for reasoning on the Time changes. I answered the why.

I'm sure there are a lot of diffs in the yards with way fewer miles on them, as well.

 

[rstcso]

The Honda Pilot called for a diff fluid change just before 6k miles based on the MM. Apparently Honda has determined one early diff fluid change is needed, typically around 6k to 10k. Supposedly, it will now pop up in the MM every 30k miles. Transmission first change is supposed to be around 30k. I'll let you know in a couple of years.

 

[raaizin]

Since the transmission and diff are atmospheric vented, whatever moisture in the air is also inside the components. And usually there isn't the heat in those components to help evaporate. You have the same issues, just on a smaller scale.

Overview:
"In addition to mileage, differential fluid must be changed after a certain amount of time because it degrades due to heat, oxidation, and moisture contamination
. This means that even if a vehicle is not driven frequently, the fluid loses its protective qualities over time and can no longer effectively lubricate the gears.
How fluid degrades over time

• Oxidation and chemical breakdown: Over months and years, the chemical additives in the fluid that help it withstand extreme pressure, inhibit rust, and reduce foam can break down. This makes the fluid less effective at protecting the gears and bearings from wear and corrosion.
• Contamination from moisture: A differential has a breather or vent that allows for the expansion and contraction of air. When the differential heats up and cools down, this vent draws air in. Over time, this process allows moisture to enter the fluid, which can turn it into a milky, abrasive sludge that accelerates wear.
• Water crossings: Driving through deep water can submerge the axle seals or vent. The sudden cooling from the water creates a vacuum, sucking water directly into the differential. If this occurs, the fluid should be changed as soon as possible, regardless of mileage or time.

What is the source of this info

 

[K-Man]

Porsche recommends trans and Diff fluids based on time as well as miles. Is there any reason for this as it seems unnecessary as there isn't combustion going on to contaminate the fluids? Shouldn't it be just based on miles?

Porsche dealers need new yachts too.

 

[Propflux01]

Is that a post from AI?

Whenever I read unspecified "chemical breakdown" I see that as "toxins in the liver" or some other fear mongering statement promoted by people that have an imagination of what is going on but really have no clue.

As for contamination from moisture, if I ever see a "milky, abrasive sludge" drain from my transmission I'll be sure to escalate the drain interval to include a time component. Until then I'll chalk this up as another phantom fear.

And as for driving through deep water crossings, well okay on that one. Again if it happens I'll make accommodations.

They”overview” is, the first part is not. A google fu search can be done easily to answer the question the OP has if I am not to be believed.

 

[JHZR2]

The Honda Pilot called for a diff fluid change just before 6k miles based on the MM. Apparently Honda has determined one early diff fluid change is needed, typically around 6k to 10k. Supposedly, it will now pop up in the MM every 30k miles. Transmission first change is supposed to be around 30k. I'll let you know in a couple of years.

My 98 Chevy S10 ZR2 had the requirement to do a 7500 mile first change in the LSD. BMW used to to changes of all fluids at 1200 miles.

As for contamination from moisture, if I ever see a "milky, abrasive sludge" drain from my transmission I'll be sure to escalate the drain interval to include a time component. Until then I'll chalk this up as another phantom fear.

I dont know about abrasive, but I recall the first time I changed the front diff on the aformentioned S-10, I was surprised at the slight tinge of milkyness indicative of some moisture being in there. Its reasonable that a system that "breathes" could have condensate, and not generate enough waste heat (in that truck the diff spins but is not under load unless 4WD is engaged, so there is no real torque transfer thus no real heat) to flash off water. See reference to my broken cam 1991 350SD's fuel tank cap rust - thats a "sealed" system, that has the ability to condense in its upper metal filler pipe. Why would a diff be any different? Now, a front diff is different than a transmission or rear diff on a RWD vehicle, for certain...

I was expecting similar when I just did the front diff of my ML320 this weekend. Of course that one is "full time", so there is more consistent torque transfer and thus waste heat generated. The fluid looked and smelled fine, no real sign of moisture, though pour-off showed some signs of wear materials.

That said, diff, MTF, and ATF fluids tend to last very well because of the lack of other sources of degradation, reasonable temperature exposures, etc.

 

[kschachn]

They”overview” is, the first part is not. A google fu search can be done easily to answer the question the OP has if I am not to be believed.

It's AI and Google that I may not believe.

 

[Astro14]

They”overview” is, the first part is not. A google fu search can be done easily to answer the question the OP has if I am not to be believed.

It’s not about your belief. It’s about the violation of the rules in the forum. You’re posting AI content, which hurts the forum. If you have an original thought, by all means share it

However, backing up your original thought with AI generated content is why the post got deleted.

 

[raaizin]

Porsche dealers need new yachts too.

I hear you, what they charge for service is obscene, that's why I maintain them myself. If its good for 120k miles I have a hard time getting it serviced for what they charge and I cant do this myself. I probably am going to leave it.

 

[tcp71]

Because Porsche wants you to have a perfect feeling and working vehicle, even if you track it every weekend. They provide a maintenance schedule that allows you to work the machine hard and still feel like new. Here's the Macan service schedule, yes, for a sedate (relatively-by Porsche standards) small SUV:

 

[Propflux01]

It’s not about your belief. It’s about the violation of the rules in the forum. You’re posting AI content, which hurts the forum. If you have an original thought, by all means share it

However, backing up your original thought with AI generated content is why the post got deleted.

I shared my original thought in the second post. I didn’t realize the AI was against the rules. I used it as a reference to the same answers given in this forum for the past 20+ years about the whys and reasonings for fluid time changes.

 

[Propflux01]

It's AI and Google that I may not believe.

Then perhaps ask the company that made the vehicle as to why.

 

[ctechbob]

On the other hand very little water gets into ATF as compared to motor oil, inside an engine there is a relatively huge about of water from the products of combustion as compared to a transmission. Add to that any mixed sulfur oxides and this is what deteriorates the TBN of the engine oil.

Ask GM 8 Speed owners in the south about that. There was plenty of water making its way into the fluid over a relatively short amount of time, enough to completely expose the problem with their fluid choice and friction system. They were finding anywhere from 1-10% in the fluids they looked at when the problem started showing up. Heat cycles and the trans having vents to the atmosphere make it a given. Add to that that an AT doesn't get hot enough for long enough to drive off the moisture and voila, contaminated fluid.

Certainly not near as much as an engine, but enough that it can be a concern over time.

 

[camrydriver111]

Because Porsche wants you to have a perfect feeling and working vehicle, even if you track it every weekend. They provide a maintenance schedule that allows you to work the machine hard and still feel like new. Here's the Macan service schedule, yes, for a sedate (relatively-by Porsche standards) small SUV:

View attachment 299559

Surprised spark plugs is shorter than air filter. Air filters must be massive though.

 

[kschachn]

Ask GM 8 Speed owners in the south about that. There was plenty of water making its way into the fluid over a relatively short amount of time, enough to completely expose the problem with their fluid choice and friction system. They were finding anywhere from 1-10% in the fluids they looked at when the problem started showing up. Heat cycles and the trans having vents to the atmosphere make it a given. Add to that that an AT doesn't get hot enough for long enough to drive off the moisture and voila, contaminated fluid.

Certainly not near as much as an engine, but enough that it can be a concern over time.

Yes it would be hard to rectify a design fault like that.