Gen4 Prius Transmission Fluid Change

Similar to what I found at 4K miles it sounds:

What did you do to your Prime today?

Thanks for sharing.

 

Thanks for sharing your technique and photos.

I’d add that the Repair Manual (more info) has two procedures for changing the hybrid transaxle fluid: an “adjustment” procedure, in which the fluid is drained and refilled once, as kindly described here, and a “replacement” procedure, in which the fluid is drained and refilled, the engine is idled in maintenance mode for 30 seconds, and the fluid is drained and refilled twice more. Obviously, there’s no need to do the latter unless you’re trying to purge the transaxle of contaminated fluid.

In these procedures, and in the one for inspecting the fluid level, the manual says to use new gaskets (Toyota part number 90430-18008) when reinstalling the filler and drain plugs for the last time. The torque specification for both plugs is 50 N·m (37 ft.-lb.), and for the No. 1 engine under cover bolts, 7.5 N·m (66 in.-lb.).

 

How about "some method for getting the new fluid in". A simple alternative is a funnel from above, with hose extension.

And you're probably fine. But personally, I would change it. As @Elektroingenieur says, if doing multiple fluid changes, change it just on the last one.

Yeah that's the key. Don't sweat how much came out, how much went in. Just have the car level when filling, and fill till it starts coming back out. Foolproof.

The transaxle fill and drain bolts I pay attention, torque to spec. With low torque "locator" bolts, I'll often just hold a ratchet wrench with one hand, over the fulcrum, twist fairly firmly.

My one gotcha: I tend to install the cover bolts loose, so the cover is free to shift as I install the plastic fasteners. Then I go back and tighten the bolts. I have forgotten the last step, and lost one bolt due to that.

I made a gizmo, mostly used for tightening the undercover bolts, convenient and acts a torque limiter:

 

Thanks for sharing this for PRIME with nice photos.

One thing I may add that I have read on Gen3 transaxle fluid change is to remove the FILL PLUG before you remove the DRAIN PLUG. This is so that just in case you have trouble removing the fill plug. If you drain the fluid first and can't refill it, you need to tow your car to get it serviced somewhere else.

 

Re: "It should take approximately 3.25qts to refill."

Is that approximately how much drained out?

Any idea what the total fluid capacity (volume) might be on this Prime transmission?

 

I believe 3.8 US quarts at refill. From the attachment in post #4:

 

I will likely hit 20K miles in my 2019 Prius Prime sometime in the next 3~4 weeks, and am planning to change to do the first transaxle fluid change myself. This is a lot sooner than the 60K factory recommendation, but it gets really hot where I live in the summer months, and since that fluid both lubricates and cools not only the gears and bearings, but also the MG stators and rotors, I figure it can't hurt to invest a little extra $$ to protect the transaxle. Just replacing the MG2 stator is supposedly almost $2,000 if it gets cooked, and contaminated fluid is listed as a high-probability cause of stator failures in the Toyota HSD transaxle. I'll change it at 40K intervals after that, unless I see from this fluid change that I should be doing it more often. I have a couple of questions: 1. What diameter are the plastic push-rivets for the engine shield? I went to buy a package of them on Amazon in case I break one or more of them, and found that there are at least 4 different sizes. Which size do I need to buy? 2. All of the instructions I've seen say that I have to pump the new fluid in. I don't own a pump. Is there some reason that I can't get like 5 or 6 feet of 1/4" vinyl tubing hose and a funnel, thread the hose down to the transaxle fill hole from somewhere above the engine, attach a funnel to the hose, and just pour the new fluid in via gravity? Thanks!

 

Humm, AFAIK, there is no factory recommendation for the transaxle fluid change.

 

Same here.

Still, sooner than later is good. My 2 cents: change it at one year mark or 10k miles, whichever comes first.

 

Yeah, I did it on my Gen3 at 30K then thinking to keep the car for a long time. Then came Prius Prime. There is no way I will be keeping my current PP longer than 3 years. I am not going to bother with anything outside of Free ToyotaCare.

 

I'm wondering if there is any necessity to replacing the fluid twice?

 

I was thinking about doing a second change soon as I am now at 54k miles.

If I do, I'll post up what I find.

 

60K mile ATF changes is the industry standard for wet clutch transmissions; 25K-30K if your towing - dependent on load capacities. No wet clutches in these transmissions; means less contaminates - cooling and lube is the main function of this ATF.
My first ATF change on my old 2013 Prius C was pretty dark @ 25K. Second change @ 75K was pretty clean - could probably stretch it out to 75K - 100k intervals w/o any issues - unless your climbing mountains or towing. That's been my experiences, based on my driving style and habits. This new PP will get the same treatment.

PS. Always loosen the fill plug FIRST!!! Don't drain it, if you can't fill it. If you don't have a new aluminum washer, just flip it over and torque to specs. They usually squeeze down and seal for 3-4 changes - this is from experience, but it should be changed and torqued properly. If they are over-torqued, they won't seal the next time you try to reuse it. If you don't have a "good" torque wrench; buy one.

Hope this helps....

 

I only did drain-and-fill transmission fluid change twice. Once on my Gen3 at ~30Kmiles and once on my 2017 PP at ~36km, but I sold both cars shortly after that. I have not bothered with the transmission fluid on my new PP so far. The 2020 PP was sold at 10mo old and 4Kmiles, and the current 2021 PP is still at 7 mo old less than 5Kmiles. I don't think I will be keeping my current PP long enough to be needing the transmission fluid change.

That is not the case for my son's Honda. It has some kind of sensor that triggers the Maintenance Minder code. I first thought that was strictly based on the miles driven, but lately, I found out that is not the case. I did CVT drain and fill on it ~15monts, 20Kmiles ago. The Maintenance Minder is now showing code B13 which is engine oil and filter and transmission fluid change. Yep, some cars require far more frequent transmission fluid change than our PP.

 

I think you mean "Always loosen the FILL PLUG FIRST." Not the DRAIN PLUG.

 

Yes, Honda has factory specific intervals for their CVTs

For other cars with NO factory specified ATF change intervals, 60K miles is a good place to start and is cheap insurance.

BTW: OEM factory lifetime fluid specification really means - When your OEM warranty expires!!!!! NOT your car or your lifetime.....

 

It's not specified interval parse. There is no mention in the manual as to the miles or months interval for the service. Rather, the reminder comes up as a Maintenance Minder service code. I once asked at the Honda Forum about what triggers the Maintenance Minder to show specific code, especially for the subcode for the transmission fluid, but could not find an answer. It does the same thing with an oil change service. It is not strictly time or miles-based as in a Prius. There has to be some type of sensor that is monitoring the quality of oil or transmission fluid, but I don't know how that works. On contrary, our Nissan Pathfinder has a specified 30Kmiles/3yr interval for transmission fluid change. BTW, Nissan Pathfinder (and I think for most other Nissans including the Leaf) also has specified brake fluid change for every 20Kmiles/2yr, which is by far the most frequent fluid change interval (aside from engine oil) of any kind for any car I have owned so far.

 

I’m thinking it uses readily available sensors, maybe engine coolant temp, ambient air temp, rpm, maybe also counts start-ups, then does the countdown to next service slower/faster, depending on factors it's gleaned.

I suspect it goes through the extras, things like coolant and transmission fluid changes and so on, in a preset sequence. But tailors the intervals somewhat, to reflect what it's getting from the sensors. Similar to regular vs severe service.

In my experience it would invariably alternate between A1 and B1 services, those being rotate tires plus oil change and oil/filter change respectively. B1 also included a brake inspection. And there'd be extra numbers for additional once-in-a-while services.

More info on the schedule in the attached, an excerpt from one manual I had, for our daughter's 2010 Pilot.