What year & miles? Transmission & gear fluid changed?

MaineHawk said:

My opinion only, and this is what I do with my variety of vehicles. My research has been if your transmission is in good shape, refreshing your fluid will improve the physical properties of your fluid, ie closer to new specs. If your transmission has worn, changing the fluid may result in slipping because the wear products in the fluid is actually helping move the car. With clean fluid it will slip. If we agree on that, how does lifetime fluid impact this thought process? There will be a point that that fluid has partially broken down. Just like he said in the video, nothing lasts forever. So eventually the fluid will have degraded and start doing damage. And if you refresh, it will be further from being the cause of failure. Doesn't mean something else won't go wrong! 😞 Looking at what came out of my transmission, I will probably repeat the drain and fill next winter. The fluid had same consistency as new, but definitely was quite dark, compared to the clear green new. Hey, new fluid will not hurt if your within "Lifetime "!

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I've been hearing more and more about the notion of once you reach a certain mileage (i.e. 150k or something), it doesn't really pay to completely drain and flush the transmission fluid for the reasons you stated. It was, however, stated that you can always add more fluid if it's reading low, which has the benefit of keeping the necessary amount of fluid in the transmission, while still maintaining those other physical properties.

I'm personally a little suspect of that, though it's obvious over time that the metals do wear and tear, and thus collected into the fluid itself. The other aspect of this is does that include transmissions where the filter cannot be easily changed like ours? The KL's transmission requires a complete removal of the unit itself, and taken apart do replace the filter. It is physically inside the casing.

In most conventional transmissions though, replacing the fluids and filter is typically an easy job, but not so in a vehicle like ours. Maybe by flushing the fluid out instead of just filling it back up, you're prolonging the life of the transmission since what is absorbed into the filter doesn't really re-enter into the fluid to circulate anyway, but the filter will continue to get more and more built up with wear metals, and other gunk that might accumulate.

Perhaps someone else with some more insight can chime in though.

EDIT: And there's the elephant in the room too. How long is "lifetime" when it comes to fluid, and from a legal perspective, could it be argued if my transmission were to blow up tomorrow, that falls under Stellantis' problem rather than mine because I, the consumer, believed a lifetime fluid meant it would last hundreds and hundreds of thousands of miles? The next question though is does lifetime constitute how old the car is, or how many miles are on it?

Interestingly, the 9-Speed in the KL, while a Chrysler-spec unit, is still a version of ZF's own 9HP transmission. And if you look at the maintenance intervals of vehicles with those exact transmissions, it certainly is not listed as "lifetime" fluids. Take the 2020 or newer Honda Ridgeline (and other Honda models) that use the ZF 9HP. There are maintenance schedules for the transmission, and do not say lifetime fluid, at least I didn't see it listed. My 2014 Owner's Manual for the Cherokee KL even states,

"Under normal operating conditions, the fluid installed at the factory will provide satisfactory lubrication for the life of the vehicle.
Routine fluid and filter changes are not required. However, change the fluid and filter if the fluid becomes contaminated (with water, etc.), or if the transmission is disassembled for any reason."

MaineHawk said:

I guess that was my point about the filter, that it must also be considered lifetime by Jeep. If so, the filter must be for larger particles but not truly cleaning the fluid of micro wear products, otherwise it would get plugged up. Periodic drain and refills removes at least some of the micro wear products that come out with the old. I think it is similar to the engine oil changes in that the internals stay cleaner when you change oil often before it is super black and contaminated. This results in less build up in small passageways. Additionally, replacing some fluid periodically should help maintain the fluid specs closer to new. This car is propelled by less than 7 quarts of fluid. After many years and many miles, it can't still be as good as new. I guess, IMHO, the fluid maintenance is much more important than the filter change.

I consider it a vicious cycle. If you wait too long, you shouldn't change the fluid, but by them saying it is lifetime fluid, it leads people to wait too long.

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Complicating this matter further, it's extremely unlikely the filter is any different than what ZF uses in their own. As far as I can work out, the only real differences between the ZF 9HP, and the Chrysler variant (which is still the ZF 9HP) is simply the mounting bolt locations. Internally, they're identical as far as I can work out, so the filters should be the same. The only difference would be simply the part number as those are brand specific. It would serve no purpose to make bespoke parts for Chrysler's own vehicles rather than using what is already provided by ZF.

Personally, I consider the term "lifetime" fluid to be hugely misleading, and I'm surprised no one has filed a class action lawsuit yet. Though, given how it would appear many don't keep their cars more than a few years anyway, they wouldn't own the cars long enough for it to be an issue.

But I've also encountered similar wording regarding the Eaton Supercharger in my 2005 Mini Cooper S. Mini had stated themselves the fluid inside the supercharger was a "lifetime" fluid. I've even spoken directly to one of the best Mini mechanics in the country, and he says that the longevity of that fluid is a "your mileage will vary." type deal. Some fluids dried up, and chewed away at the gears after 30k miles, and others he said lasted nearly 250k miles before a service.

In my case, I serviced the supercharger at about 168k miles, and to my surprise, there was still a lot of fluid left in it. Could've easily lasted into 200k miles I reckon. But considering the supercharger drives the water pump, plus there's a lot of seals and gaskets, you might not even reach the end of its "life" on the fluid before other components wear out first.