No transmission oil change intervals?

The transmission is always working, whether in EV or hybrid mode. I have the same car and aim to replace the atf every 100,000km.

 

Some maintenance guides have listed a periodic inspection for the ATF. I've never seen one that actually indicated periodic replacement, nor have I seen anything that listed inspection criteria.

But what's up with that inspection? I mean, what are you going to do, look at it, shrug and put the plug back in? Verify level? Smell? Shavings per gram test? Makes me think they just wanted to write something in the maintenance guide and couldn't come up with anything better.

But we should reconcile this with the fact that quite a few Priuseses already went from factory to crusher with just one dose of oil in the gearbox and no regrets, and the scrapyards are still full of usable Prius transmissions that nobody wants because nobody seems to be wearing them out.

If you never overheat your lubricant and never expose it to contaminants, it should last a ridiculously long time.

 

Prior to gen 4 Toyota Canada published a schedule, included it in the booklet that accompanied the Owners Manual (name escapes me).

Over the years I’ve seen its format varied between awkward and clear. 2014 was an example of the latter: table format, with rows of service description, columns of months/kms.

then, for model year 2016, they “stopped”. No explanation, just relegated the whole thing to a web page, and no summary table, just a dialogue: tell us your miles/momths, and we’ll tell you what needs doing. Progress…

if you’re a gluten for punishment, you could repeat the exercise and reverse engineer a table format summary. I’ve done that using the US Warranty and Maintenance Booklet, which at least publishes an event-by-event format schedule, for the 2nd through 4th gen, haven’t bothered with 5th.

Toyota Canada and USA are aligned on this, both saying nothing. My 2 cents: change it around 16k kms, then again, say around 64k kms, and that might do it for the duration. That’s based on my 3rd gen experience, doing 3 changes, and just judging by how much it had darkened.

there’s a link in my signature for 3rd gen transaxle fluid change, fwiw. For fourth gen the drill is very similar, fluid spec still Toyota ATF WS. (On a phone turn it landscape to see signature).

 

Yes, it really is not a transmission with gears, clutches and shifting. It's called a Power Split Device or PSD and you can look it up on YouTube. Most people will never have to drain/refill the fluid as long as they own the car. But, if you must, I would simply let the dealer or an indy mechanic do it for $200-300 because after all, you might do it once during the life of your car. Just be sure to use only genuine Toyota fluid.

 

Anything over $100 is robbery; the complexity and time involved is on par with an oil change.

 

Toyota states that it's a lifetime fluid. The way I read that, whenever the Toyota warranty expires - NOT YOUR lifetime. My engineering experience and two generations of automotive mechanics guts tells me - nothing last forever. Fluid breakdown through wear, hot/cold cycling, and contaminant loading - the fluid needs to be changed at some point.
IMHO and experience with Prius, most contaminant loading happens during the first 25K miles, fluid is dark and dirty. I performed another change around 80K miles, slightly dirty - but noticeably lighter in color than the first 25K mile change. I'd estimate 100K mile transmission fluid changes should be a significant change interval - but if your towing or under "extreme conditions" - constantly heavily loaded up; I'd probably do 50K-60K mile changes, to get a guesstimate of how often you should change it.
In my dad's transmission shop, we recommended and did 30K transmission fluid changes on tow vehicles - never had a failure. Most of these customers was word-of-mouth, after rebuilding several club member's transmission that meet an early demise.

Just my two cents on the subject, take it or leave it....

 

You did an earlier, initial change? I’d concur with that, an early change is beneficial, just judging from colour, and with subsequent changes the colour is progressively less darkened.

 

This is the critical takeaway. It's just a planetary gearset and a differential. It has less to do with a "transmission" as we traditionally think of it, than it does just a differential. Planetary gears are just a different way of making a differential. I'm a mechanical engineer and find a lot to nerd out on the idea. It's really quite clever.

Say you had a RWD or AWD car; you would change the differential oil in your car once every so often, so change your "transmission" fluid just as frequently.

 

Your correct, but the internal bearings (wear surfaces) are affected by fluid contaminate load and lowers the efficiency of the cooling properties of the ATF two critical factors. The two main reason tow vehicle transmissions go out, neglect, and the thermal breakdown of the ATF. A lot of heat is generated, when dragging a trailer - especially up hill. I know newer Honda Pilots has installed ATF temperature sensors.
My friend is hard on cars and tripped that code twice. Told him to change the ATF every 30K miles and install an aux. transmission oil cooler a few years ago. He's pushing 200K miles and never tripped that code again.

 

My take, having done 3 changes on ours, is that a first fluid change, quite early (say 12 months or 10k miles), is most beneficial. I’d speculate due to machining detritus, initial gear meshing, liquid gasket leaching or whatever. Second drain was markedly cleaner looking, even with longer interval. With third change I vowed to knock off for a good while, lol.

 

Not sure if you mean motor oil or transaxle fluid change. I have descriptions of my workflow for both, in links in my signature. If you're on a phone you need to turn it to landscape orientation to see signatures on this site.

Even it it's just the transaxle fluid change you're interested in, the oil change link (in my signature) also has some thoughts/tips on raising the car, dealing with underpanels.

Those descriptions are 3rd gen 'centric, but 4th gen I believe is very similar. I'll attach (as best I can, till @Danny fixes things) an excerpt from the fourth gen Repair Manual:

(clicking arrow in upper right corner should "open" the pdf in a new tab on your browser, and provide a download option)

Going from 3rd gen to 4th gen, the main diff I see is some increase in the rhetoric regarding keeping the transaxle's plugs installed as much as possible during the drain-and-fill process, I think to placate some engineer. I wouldn't go nuts, just do it expediently, don't leave it sitting open for days. Again, only use fluid from freshly opned bottles, and just recycle any leftover.

 

I love magnets, but they only catch ferrous contaminants - what about the other contaminates ie. silica or anything else that makes it into your transmission.

IMHO - Cheap insurance to just do an early change around 20K and then every 100K thereafter.

Bottom line, it your car - do whatever you like....

I did the ATF change on my slightly sloping drive way. The slope was a very close match to the low profile ramp I use. Remove the fill plug - if very slow drip, follow OEM procedures. If ATF pours out or fast drip, car isn't level enough; readjust before proceeding.
Top fill with a hose and funnel is easiest or try one of those harbor freight battery operated fluid transfer pumps (<$10 on sale).

Hope this helps

 

I'd agree for a normal automatic transmission - yet has anyone ever heard of a planetary gearset fail on this car? I'm fairly certain mine is original fluid at 263k miles. There's something to be said for "it just doesn't seem to break"

 

Yes, but I'm still with @BiomedO1: for $40~50 for the fluid and drain/fill bolt washers, and about an hour of your time, one early change looks to be clearing something out, beats letting that stuff sit in there for the duration.

If DIY is not doable, an independent mechanic with a lift could do this in half-an-hour I think. Bring them the fluid and washers for sure. Maybe an new funnel and hose (keep OD to 5/8" max, to fit) as well, to avoid contam'ing the fluid.

 

I've seen planetary gear sets fail, in my dad's transmission shop - but it is a rarity and mostly on American cars. The few foreign cars this happened to; the transmission literally imploded. The car must've be slipping and wining for years and the internals (what was left of them) was covered in sludge and varnish. Whenever this happens; we usually rebuild junk yard unit and install it, because it's more cost effective than trying to replace all the bad "hard" parts.
Bottom-line, you can trash and abuse anything.