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Ascent CVT failures?


hkshooter
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Ive been poking around the net and come up dry concerning this, maybe I missed something.

I know of multiple complaints about the Ascent but the most disturbing is vehicles going into the shop for CVT problems and failures. Ive heard of one failure and a second problematic unit. These are SIA employees and not rumors.

Anyone of you heard any rumblings of such?

 

 

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I recall reading some threads on the Ascent forums about it. I don't recall many details though, maybe head over there to see what owners are saying. Is the CVT in the Ascent the same one going into the Legacy and Outback XT?
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Most likely they are using the same unit in the Legacy and Outback XT as the Ascent, but it may have different software and some minor changes to better match the vehicles.

 

 

If there are failures, I think that it's best to first determine what kind of failures there are and if they have the same root cause. Deeper analysis is needed before saying that it's a general problem.

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There are a few cases on the Ascent forum about failures. There was a hunch that it was related to a September 2018 delivery last year which may have suggested a bad supplier part or something.

 

Remember:

 

There are tens of thousands of Ascents on the road now. A handful of CVT failures is a minuscule amount. This is what your warranty is for.

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Ascent uses the TR690 transmission that was first used in the 2010-2012 2.5i Legacy/Outback's. 2.5i's then switched to the TR580 around 2012. TR690 was then reused in the 2015+ Legacy/Outback 3.6L and WRX. They are labled High Torque, contain more chain-links on the actual CVT chain, and use different high torque CVT fluid.

 

The transmission it self has had 10 years to bake in, but at much smaller scale then the non-High Torque versions, simply because 2.5i's outsell 3.6's and WRX's by a far margin. Some say 10:1, but I haven't really been able to find the exact number.

 

Now the Ascent is also 500-1,000lbs heavier and has new turbo motor with more torque then the the previous TR690 powered Subarus. Ascent also has automatic dual mode X-Mode, which allows for all 4 wheels to spin freely to brute force you out of a stuck situation, previous models would simply stop spinning any wheels if all 4 where slipping (hence the introduction of Dual Mode X-mode). This matters because free spinning wheels can damage the CVT, which is why I believe previous models would cut power completely.

 

Ascent Xmode Tested:

[ame=http://www.youtube.com/watch?v=GZ4aeC2Uvm8]Subaru Ascent: AWD diagonal test in DEEP SNOW! I'ts X-MODE time! - YouTube[/ame]

 

Dual mode X-Mode tested/explained, at 6:00 he shows the different between old x-mode and new x-mode

[ame=http://www.youtube.com/watch?v=6U4WLc2V-LM]2019 Forester Dual X-Mode Explained and Real World Test #drivingsportstv - YouTube[/ame]

 

With that said, the failures seem to be mostly in the July-October 2018 build range and failure seems to happen within the first 10k miles. Tell tell signs is similar to a slipping clutch and along with screeching noise, but once the car cools down it seems to go back to normal, until it completely fails. Some are fine after replacement, others started showing symptoms again, at which point the wiring harness has been blamed (if the car didn't get lemoned first).

 

Full thread can be found: https://www.ascentforums.com/threads/major-transmission-problem.4809/

 

This is one of the reasons I'm still sitting on the sidelines and haven't jumped in the an Ascent just yet, and probably why I'll avoid used 2019 stock too.

 

Also for those that are curious, the TR690 and TR580 designations are for the torque capacity in Newton Meters. This is pretty well explained in this post.

FWIW, the Subaru model numbers on the CVTs (G1: TR690, G2: TR580) appear to be directly related to their rated torque capacity in N-m. Transmission torque capacity should always be higher than max engine torque times maximum torque converter ratio. Examples (torque values per 2015 Legacy/Outback FSM):

 

FB25 engine + TR580 CVT (2015 Legacy/outback):

Max engine torque = 235 N-m

TC stall torque ratio = 2.07

Max torque input to CVT = 235 x 2.07 = 486 N-m

Presumed transmission rating = 580 N-m

Presumed design margin = 580 / 486 = 119% (i.e. safety factor = 19%)

 

EZ36 engine + TR690 CVT (2015 Legacy/Outback):

Max engine torque = 335 N-m

TC stall torque ratio = 1.80

Max torque input to CVT = 335 x 1.80 = 603 N-m

Presumed transmission rating = 690 N-m

Presumed design margin = 690 / 603 = 114% (i.e. safety factor = 14%)

 

Now the Ascent has 376 N-m of torque and unknown TC Stall ratio, but if we assume 1.80 like the H6 models we get 676.8 N-m, which is much closer to the limit then previous models.

 

TL;DR: Much higher percentage of the TR690 being used in the wild + heavier car + new torquer motor + new free spin X-Mode = Higher numbers of failures, even if the percentages might be about the same.

Edited by covertrussian

05 LGT 16G 14psi 290whp/30mpg

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

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In Europe the diesels also had the high torque CVT, not sure if that also has the designation TR690. They have a different software mapping compared to gasoline engines though.

 

 

At least the diesel engines really benefited from being mated with the CVT. And the diesel also had about 350Nm (260 lb⋅ft) of torque.

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I have to wonder if thinner fluid is aggravating the issue. I've read that's something they changed to lessen parasitic drag in the CVT to help inrease fuel economy. Feels like a bad idea to me but I'm no engineer.

 

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In Europe the diesels also had the high torque CVT, not sure if that also has the designation TR690. They have a different software mapping compared to gasoline engines though.

 

 

At least the diesel engines really benefited from being mated with the CVT. And the diesel also had about 350Nm (260 lb⋅ft) of torque.

 

Do they still have the fake shift points in Europe? I kind of wonder how they changed the mapping to better accommodate diesels (keep it in lower gears more?)

 

OT:

What kind of fuel economy are those CVT diesels getting? How does it compare to the traditional AT's and MT's? Just curious if CVT makes just as big of a fuel economy impact on diesels as on gas engines :).

 

 

I have to wonder if thinner fluid is aggravating the issue. I've read that's something they changed to lessen parasitic drag in the CVT to help inrease fuel economy. Feels like a bad idea to me but I'm no engineer.

 

Sent from my SM-G950U using Tapatalk

 

From everything I've seen/heard the High Torque CVT Fluid (Orange) is the same as it's been since 2015. All but Base Ascent's also have CVT coolers, which should help them tremendously too (heat is the enemy of any automatic).

 

I really do think the higher failure rate is due to increased amount of TR690's then anything else. Subaru Ascent's have sold little over 80k in one year. While other models are doing about 10-20k a year with that same transmission (without an CVT cooler too).

 

Now Subaru has been having quality control issues, perhaps the manufacturer of the TR690 parts just can't keep up?

05 LGT 16G 14psi 290whp/30mpg

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

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Do they still have the fake shift points in Europe? I kind of wonder how they changed the mapping to better accommodate diesels (keep it in lower gears more?)

 

 

Unfortunately they have them if you are "inspired" with the throttle, but they aren't there during normal driving.

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Ascent uses the TR690 transmission that was first used in the 2010-2012 2.5i Legacy/Outback's. ....

 

Now the Ascent is also 500-1,000lbs heavier and has new turbo motor with more torque then the the previous TR690 powered Subarus. ....

 

Now the Ascent has 376 N-m of torque and unknown TC Stall ratio, but if we assume 1.80 like the H6 models we get 676.8 N-m, which is much closer to the limit then previous models.

 

TL;DR: Much higher percentage of the TR690 being used in the wild + heavier car + new torquer motor + new free spin X-Mode = Higher numbers of failures, even if the percentages might be about the same.

 

Don't forget the Legacy 2.0DIT, WRX S4 and the Levorg 2.0GT. They have 295 lb-ft (400N-m) engines. If we applied the same calculations to the FA20DITs with the EZ36 TC ratio, then the FA20DIT is 5% over the safety limit.

 

Is there a big fail rate with the FA20DIT cars? That said does anyone know what torque converter is used on those Subarus? I recall I saw a press release post about revised torque converter somewhere but I have not had time to search for it.

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The failures I have seen on ascentforums.com definitely were manufacturing defects, I don't think anyone has killed this cvt yet...but it does make me think more about longevity of it. We have about 5K miles on ours and about 500 of those miles towing a Jayco 22bhm at about 4.4k Lbs and 24 feet long. Aside from truck wash it has towed really well, I do wish we could monitor CVT temps, but noone has come up with a solution for that yet. The one app that some thought was working turned out to be mirroring coolant or oil temp with the CVT temp.

Also to add to the shift point perception, you feel them more in low speed conditions, smooth throttle input makes most "shifts" imperceptible, I wish they would just do away with the fake shift points they seem to cause more issues than they solve.

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Torque converter was changed from a throw out style to a washer style following some issues in the 2010-2012ish mode Outbacks. It was repaired on my former ride.

 

My 2011 Outback had the TR690 and it was fine. No shift points. When I put my Forester into “S” mode it reminds me of it. It was a little torquey off the line and slow in the mid range. My Forester In I more is smoother all around. Much better tuning I think.

 

Regarding the parasitic drag they removed some pulleys or something relating to when they formed the 580 from the 690.

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  • 2 weeks later...

Looks like Ascent's have a different CVT fluid afterall. CVTF-LV (P/N - SOA748V0300). Even though it's clear/amber like other HT TR690 fluid Subaru is claiming it's Ascent specific:

 

Found in Robert's post over at Ascent forums.

 

screenshot_20190816-224043_drive-jpg.1220

 

Update: Robert posted a dedicated thread that further explains it: CVT Fluid - SOA748V0300

Edited by covertrussian

05 LGT 16G 14psi 290whp/30mpg

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

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Yes covertrussian - this had been confirmed when the Ascents first came out last spring.

This lower viscosity flavor of the amber CVTF can still be replaced or partially flush-out mixed with say Mitasu MJ-329 or Amsoil CVTF.

 

Thanks for chiming in, after I posted that, I found your discussions about SOA748V0300 from 2018 over at the Nasioc.

 

Perhaps that's the reason we are seeing higher Ascent CVT failure then with WRX/FXT/Other HT TR690's?

 

Do you know why they went with the lighter stuff, strictly fuel economy or another reason?

05 LGT 16G 14psi 290whp/30mpg

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

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  • 3 months later...

There is finally a recall for the CVT failures! It's related to dissimilar metals in the transmission harness corroding and increasing sensor resistance. Which led the TCU to believe the pressure was higher then it really was, thus it would reduce the clamping force on the chain causing it to slip.

 

CVT chain slipping would not only score the CVT pressure cones, but would also increase the CVT fluid temp, which can melt the components of the valve body, I believe this is the same issue that high power CVT WRX run into.

 

Full description can be found here:

https://static.nhtsa.gov/odi/rcl/2019/RCLRPT-19V855-2068.PDF

 

Now the official fix is ECU/TCU tune update. Which seems to make the ECU smarter and more resilient, by either using more then one input to determine the clamping pressure, or by going into failsafe mode to prevent transmission damage. Subaru seems confident in this solution, thus they are not replacing all of the not-yet failed harnesses (ecu re-flash on 77k cars is easier and cheaper for sure). I'm glad they are fixing it, but I'm not sure I would be comfortable buying a used one either though.

05 LGT 16G 14psi 290whp/30mpg

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

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Good info. Subaru's next list of re-progamming PAKs will likely include this.

 

The current/latest (Oct-2019) as of this writing only has Oct-2019 ECM reflashes for the Ascent that do NOT yet mention anything related to the HTCVT, ECM/TCM interaction. Makes sense.

 

https://techinfo.subaru.com/stis/doc/otherMisc/Reprogramming%20J-2534_October_2019.pdf

 

Interestingly, there are a bunch of VDC reflashes available for older HTCVT WRXs (dated Apr-2019) listed.

DTC C1531, DTC C1741 related.

 

Nothing for those cars or the HTCVT Legacy/Outbacks since their old ECM/TCM reflashes years ago.

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What about a new one? Should I be comfortable with a brand new Ascent off the lot, or should I wait for this issue to be resolved?

 

Now that they found the issue, I would feel more comfortable, as long as it has the new similar metal harness. I would consider extended warranty though too, but that's because I don't trust CVT's to last in a higher powered 4,500 lbs vehicles.

05 LGT 16G 14psi 290whp/30mpg

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

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  • 1 month later...

Jan 2020 reprogramming packs are out:

https://techinfo.subaru.com/stis/doc/otherMisc/Reprogramming%20J-2534_January2020.pdf#search=J2534

 

And as expected, the Oct-2018 ECU reflash for the Ascent is listed.

No TCM reflash listed though.... odd.

 

ECM 2019 ASCENT 2.4L Turbo CVT (FED, CAL)

PAK 22765AL732

Addresses: P0045 and P2196

(Release: October 2018)

 

Only noticed some recent current-gen Forester CVT TCU reflashes.

All others are earlier 2018 Mode $04 correcting reflashed. Boring.

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  • 1 month later...

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