Is my transmission going bad?

[ammcinnis]

Plenty of Prius drivers can attest to the bulletproof [CVTs] they own.

Apples vs. oranges. The Prius transmission is a brilliant engineering tour de force, but its design is totally unsuitable for any vehicle powered solely by an internal combustion engine.

 

There is also the matter of scale. A Prius transmission operates at power levels much lower than any recent Legacy or Outback. Limit operation of a Subaru CVT to Prius power levels and it will likely last forever.

Edited January 27, 2022 by ammcinnis

[DougKelly20]

I'm having trouble using the quote feature which seems to have disappeared from the Tapatalk interface, but on the subject of heat in the CVT on freeway vs stop and go traffic I'm noticing it has more to do with ambient temperature and time driving.

 

While yes in general it might heat a bit faster in stop and go traffic, hard acceleration and up hills, it does so in general slowly, over time.

 

For example it's about 10 degrees here in NY lately and after about 10 minutes of warming up (yes I use remote start, yes I realize the car doesn't need that long but I prefer not to freeze my a$$ off), the CVT starts out my journey to work at 40 ish degrees. I have stop and go for half my commute and highway for the other half of a 35 minute commute. By the time I get to work it's around 100 degrees. During that time it warms up in a linear fashion a couple degrees at a time.

 

It then stays hot for a while. If I run errands back to back then take the highway home or visa versa, it just keeps climbing the longer I run the car.

 

There are limits to this. It will eventually level off....after a track session when it hit 250 degrees I let it sit for 2 hours and got back in it and it was around 190 again. After hot lapping it for 15 minutes it was back to 250 (where I cut it off) and on my highway drive home it slowly dropped back to around 200 to 180....this was in the summer when it was 90 out.

 

In the cold it has kept climbing past 140 the longer I stay on the road. Once at a constant highway speed you'd think it would stay static and I'm sure eventually it gets there but it takes a long time to warm up and cool down....MUCH longer than coolant and oil, and so to summarize I really feel like ambient air temp and duration of trips has more to do with it than stop and go vs highway.

 

From what I remember the optimal range is 85-175 and it's really not good when it gets way up to 250. Given the fact that Japan and Canada recommend certain intervals closer to (36mi and 50kms I think?) And the fact that it's fairly common to have the opinion "all fluids eventually wear out" I would say change it....if it's drained instead of forcibly flushed I can't see what would go wrong.

 

Personally given the track time mine will see I'll be installing a CVT cooler this year and having the fluid changed at the same time. It has 47k on it today.

 

Hope that helps.

Edited January 27, 2022 by DougKelly20

[ammcinnis]

In "normal" highway cruising ... 65-75 mph at moderate ambient temperatures ... the CVT fluid temperatures in my two Subarus (2015 Legacy 2.5 and 2016 Outback 2.5) usually stabilize at about 190-195 degrees F. The highest CVT fluid temp I've ever observed was in the Legacy, cruising across west Texas at 75-80 mph, into a substantial headwind, on a 100+ degree day: ~215 degrees F.

 

The biggest single heat source in a Subaru CVT is an unlocked torque converter. (Typical TC efficiency, unlocked, is around 80-85 percent.) The Subaru TC is usually unlocked only at speeds below 10-20 mph. Worst case for fluid heating is probably when slogging along off-road, uphill, at low speeds, for an extended period of time.

Edited January 28, 2022 by ammcinnis

[Brisvegas]

As for the fluid change, I cannot fathom why Subaru doesn't recommend some kind of periodic fluid replacement for their CVTs. I understand the longer oil change intervals are largely due to euro-spec regulations, but I don't think that applies in this case.

 

Other members might disagree, but I personally would agree with your comment about periodic fluid replacement.

 

But seeing as how you did bring up the Prius reference, I think it's only fair to point out that Toyota do not recommend a fluid change in Prius CVT's either .... (just saying)

[ncted]

Apples vs. oranges. The Prius transmission is a brilliant engineering tour de force, but its design is totally unsuitable for any vehicle powered solely by an internal combustion engine.

 

There is also the matter of scale. A Prius transmission operates at power levels much lower than any recent Legacy or Outback. Limit operation of a Subaru CVT to Prius power levels and it will likely last forever.

 

What I get from your response is the Subaru CVT is not an engineering tour de force.

 

Anyway, we'll see how it goes. Subaru doesn't feel like it killing it on reliability like they used to though.

[ammcinnis]

What I get from your response is the Subaru CVT is not an engineering tour de force.

Then you are mistaken. After 6+ years and 55,000+ miles, I still consider the TR580 CVT in my 2015 Legacy to be one of the car's best features. But except for the Variator assembly, which is sourced from a third party, the Subaru CVTs are rather straightforward, unremarkable designs ... and I mean that as a compliment.

[ncted]

Then you are mistaken. After 6+ years and 55,000+ miles, I still consider the TR580 CVT in my 2015 Legacy to be one of the car's best features. But except for the Variator assembly, which is sourced from a third party, the Subaru CVTs are rather straightforward, unremarkable designs ... and I mean that as a compliment.

 

I have no complaints about the function of the CVT in my Legacy. I quite like it compared to the 4EAT in our Forester XT.

 

I am just concerned by the almost Schrodinger's Cat kind of situation when it comes to reliability. It might be reliable in the long term or it might not, but don't open it up to find out because that will change the decay rate.

[Limeymike]

Subaru Canada and Subaru Japan both have CVT fluid changes at regular intervals. Only Subaru USA says it is lifetime.

[donglow2]

My 2019 Legacy is at 184,200 miles on original fluid. My driving is 95% freeway and up to now there have not been any issues. My dealer still would not suggest changing the fluid and I am feeling that doing so at this mileage may cause issues.(?) So, I am in a quandary, change it or leave it alone. Obviously the resale value of the car is poor (9K trade In) so I intend to run it until it becomes economically not worth it. Before the Legacy I had Toyotas and 300,000 was the norm before any mechanical catastrophy. What would you do?

 

Mike,

In addition to my Legacy, I have a 2013 Impreza that has similar mileage and was in a similar situation on whether to change fluid It has the same TR580 transmission. Here is a little I have learned and experienced. CVT fluid has friction modifiers to help keep the metal belt from slipping, in addition to the lubricant and other qualities ATF has. Unlike AT's the likelihood of slipping increases as the lubricant breaks down from age. I replaced my Impreza fluid at 175K with Redline non-slip CVT and the car drove way better! Well worth it! I can't tell you the science if Red Line is better than stock for high mileage but I can definitely say it worked great for me.

 

Some other recommendations are to do the change with or without flush yourself. It is not that hard, will save you a ton of money, and you will know it was done right. As far a no dip stick transmissions goes it is way easier than a 8 or 10 speed toyota/lexus. After I get used to the forum here maybe I will start a thread on it. But if anyone wants to do it now just follow Mr Subaru video

If you want to drop the pan and clean the magnetic and maybe replace the screen add in a youtube on doing that like

If you want to go all the way and do a flush there are youtubes on that too. [Redacted by mod] Edited February 27, 2022 by ammcinnis
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