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To the Subaru Ambassadors. I bought a new 2020, Dec. 2019. Since new, I’ve had this problem as I accelerate from a bit of a “coast” or no load usually headed uphill. Transmission shudders momentarily then smooths out. Unfortunately it doesn’t happen all the time so when test driven, they can’t replicate. No lights come on, etc. I’ve read of a number of similar cases since the Ascent was introduced. My dealer denied knowing anything about these issues in the past. Just 2 days ago, they received a related service bulletin, but I guess it didn’t apply to my situation. Unfortunately I wasn’t present at the dealership to go for a test drive with the technician, will do next time.
When the satisfaction survey came out shortly after my purchase, (4th Suby) I did add a statement relative to the impression I got that there were no problems with this model. Never got a response which I thought was quite poor. At least acknowledge the problem. I just find it extremely frustrating, hard to understand why an upstanding company can bury people’s concerns. So.... is there a problem and hopefully a solution?
 

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Just 2 days ago, they received a related service bulletin, but I guess it didn’t apply to my situation.
I'm really curious to know what this new service bulletin is referencing!

Our 2020 Ascent (Feb 2020 build) has a similar shudder/studder sometimes when you transition from no load to acceleration. As you note, it's very intermittent and inconsistent to reproduce. I think there are several threads on this forum related to the topic. I've had our dealer look at ours and, naturally, they could not reproduce the problem.
 

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Browse through them here. Scroll towards the bottom for the list.

Excellent! Obviously Subaru is aware and looking into the issue. For anyone curious, here's the PDF document that has all the info. This PDF is from the link djrussell provided;

MC-10188160-0001.pdf (nhtsa.gov)

Something of note is that during the troubleshooting tree is a step where the transmission can be reset into it's initial learning mode. Perhaps all the problem is, is that a new owner drives conservatively, then later changes driving pattern to one more familiar with the vehicle but the tranny has 'learned' the initial driving pattern. A reset might be all that is required to retrain the tranny to the driver's new style of operation. I know there's a difference between how I drive and how my wife drives and that the stutter happens a lot more when I'm driving than she. (BTW my wife is much more the aggressive driver, but hollers at me when I drive to slow down. Ha! I average 24mpg, she averages 19mpg. Which might be a clue as to the stutter; what is your mpg for those who experience the stutter?)
 

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To the Subaru Ambassadors. I bought a new 2020, Dec. 2019.
Alas, just an FYI, though I am very active in assisting with Ascent issues, I'm one of a very tiny handful (under a half dozen of the 20,000 of us) who does so.

Since new, I’ve had this problem as I accelerate from a bit of a “coast” or no load usually headed uphill. Transmission shudders momentarily then smooths out. Unfortunately it doesn’t happen all the time so when test driven, they can’t replicate. No lights come on, etc. I’ve read of a number of similar cases since the Ascent was introduced. My dealer denied knowing anything about these issues in the past. Just 2 days ago, they received a related service bulletin, but I guess it didn’t apply to my situation. Unfortunately I wasn’t present at the dealership to go for a test drive with the technician, will do next time.
When the satisfaction survey came out shortly after my purchase, (4th Suby) I did add a statement relative to the impression I got that there were no problems with this model. Never got a response which I thought was quite poor. At least acknowledge the problem. I just find it extremely frustrating, hard to understand why an upstanding company can bury people’s concerns. So.... is there a problem and hopefully a solution?
A torque converter lockup during certain speed hill climbs may cause a one-time shudder that feels like a misfire. That can also happen on flat roads. Mine smoothed out over time, and I don't notice it. It is normal. Some people never notice it, because their driving habits rarely make it happen - so, once the lockup clutch learning is farther along, even if they do hit a hill at the right speed, it doesn't noticeably happen.

There is a torque converter lockup relearn they can perform, but, that won't necessarily make it "better" - it restarts the whole learning process, which may bring you right back to the beginning.

As for the TSB, in the TSB they found, it refers to issues with other clutch packs in the CVT. The computer (TCM) would show very specific data for such an issue, so, if they deemed it didn't apply, it's because (a) the data results showed normal operation during the "shudder" or (b) they couldn't recreate the situation (in which case, it's either normal or abnormal, but, they wouldn't know).

If it's a one time shudder on such things, it'll probably smooth out, like mine and many others did. If it's repeatedly doing it (multiple shudders on the same hill), that's likely something else that they need to be able to replicate. It's VERY important they replicate it. The solutions are, depending on the data (a) start the lockup clutch relearn, (b) replace the TCM, (c) replace the whole CVT.

So, the repair is simple (press a few buttons on the SSMv4 while it's plugged into your car) or mostly simple (replace the TCM) or more complex (replace the whole CVT). Because of that, there's not much they can do until they can replicate the problem and get data from the SSMv4 so they can figure out what's causing it.
 

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I'm really curious to know what this new service bulletin is referencing!

Our 2020 Ascent (Feb 2020 build) has a similar shudder/studder sometimes when you transition from no load to acceleration. As you note, it's very intermittent and inconsistent to reproduce. I think there are several threads on this forum related to the topic. I've had our dealer look at ours and, naturally, they could not reproduce the problem.
How many miles do you and @Rick H Can have?
 

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Ours has nearly 10k miles. The shudder was not apparent early on, became progressively worse in the 4-8k mile range I'd say, and has been very intermittent since then. I think I remember it happening once this week, but maybe...and only just that one time in recent memory. I do drive it in manual mode regularly (probably half the time) and it tends NOT to happen in manual mode. I tend to think that it's not a slip of a chain or a clutch, but it feels like a "sticky" sensation when the variator pullies adjust. I'm not saying that's what it is, but that's what it seems to be, given the circumstances under which it happens for us.
 

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Excellent! Obviously Subaru is aware and looking into the issue. For anyone curious, here's the PDF document that has all the info. This PDF is from the link djrussell provided;

MC-10188160-0001.pdf (nhtsa.gov)

Something of note is that during the troubleshooting tree is a step where the transmission can be reset into it's initial learning mode. Perhaps all the problem is, is that a new owner drives conservatively, then later changes driving pattern to one more familiar with the vehicle but the tranny has 'learned' the initial driving pattern. A reset might be all that is required to retrain the tranny to the driver's new style of operation. I know there's a difference between how I drive and how my wife drives and that the stutter happens a lot more when I'm driving than she. (BTW my wife is much more the aggressive driver, but hollers at me when I drive to slow down. Ha! I average 24mpg, she averages 19mpg. Which might be a clue as to the stutter; what is your mpg for those who experience the stutter?)
I have the exact same scenario! Mines a 2021 Ascent Limited and every time I drive it I get a quick shudder when power comes on when beginning a gradual incline. My wife does most of the Ascent driving and she is more aggressive with the throttle than I am. Different driver profiles is an interesting dilemma.
 
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