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High Speed Vibration - Revisited

9K views 9 replies 9 participants last post by  Jim_in_PA 
#1 · (Edited)
I picked up my Ascent (Abyss Touring) about a week ago. There are approximately 800 miles on the odometer.

I've noticed that at high-speed (70mph+) I am detecting a subtle, fast vibration that is accompanied by a low-pitched drone. My immediate reaction was to have the alignment and wheel balance checked. The front toe was slightly off and both driver's side wheels needed a 10g weight to balance out. I also adjusted the cold air pressure to 33psi. I thought I had finally solved my problem.

Last night I decided to put it to the test and went for a drive across a variety of surfaces while varying my speed as much as possible. Unfortunately the vibration persists. It seems to happen most often when the engine is at 1500-2000RPM. Increasing the RPM seems to mitigate the problem although I have felt it at 2100+RPM. I wonder if I'm feeling the engine being lugged a little? Keep in mind this is a very subtle vibration. If staring at the steering wheel, it is not visible.

I've also noticed this to be most prominent on concrete road decks; especially those just completed near my home. Could it be that I'm just getting more feedback in the wheel than I'm used to? I have experienced this on smoother roads as well though.

Lastly, this might just be a perception thing. My last two cars were V8 and V6 respectively. The latter was so smooth it was almost undetectable when running. I don't mind the little boxer in the Ascent but compared to previous vehicles, it is not as quiet or smooth.

Also my last car had 40-series tires on 19in wheels and I don't recall there being as much feedback in the steering wheel.

Has anyone else experienced this?
 
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#2 ·
I'm trying to understand your explanation and it's likely boiled down to 3 area of issues:

1. drivetrain vibration;
2. engine configuration (H, I, V); and
3. steering feedback.

At about 1500-2000RPM on our Forester, the tranny, front/rear differential, or traction control appears to behave very awkward. It's easy to say that the CVT is slipping or something like that, but I think there's something else more complex than the shifting, like evaluating the entire AWD system. I know you're looking for specific answer but the given information you provided affects all of the components I identified. If I have to guess, it has to be the traction control system that's giving you the feedback.

The H4 engine sound loud inside the cabin or stand by the car? Read this article about the sound and it may give you a slight insight of the sound.

I believe the ascent has electric steering, different than the traditional hydraulic steering type. Maybe someone can confirm about the steering feedback.
 
#3 ·
I'd like to revisit this (again).

Since I last posted, I've had some more time to dig into this and also compare against our 2018 Outback. I think what I'm experiencing actually 2 different things.

1. There is subtle vibration and nearly any speed which I have noticed occurs when the engine is under 1500 RPM. Our Outback does the exact same thing. Simply the vibration of a 4-cylinder motor at low RPM being transmitted to the steering wheel.

2. At speeds of 73-76 there is very subtle, yet rhythmic vibration in the steering wheel. I tried changing down to a lower 'gear' to increase engine RPM and there was no change in the vibration. This does not occur at all times and could be attributed to the road deck but I am skeptical due to the rhythmic nature.

To give an idea of the intensity of the vibration I describe: it is not enough that it's visible in either the wheel or my hand.

Tires have been rebalanced and tire pressure is at the recommended 33psi cold. Does anyone else experience this?
 
#4 ·
I have exactly the same problem with Abyss Limited Ascent, i have 800 miles on it. I feel the vibration on 1500-2000rpm. I checked with dealer and they re-balanced tires and they exactly did what you mentioned in your initial post. The problem still persists. I tried driving another ascent and it has same problem too. Since the vibration is only under few scenarios, most people may not notice it. Its little bit freaking me, i want that to be fixed.
 
#6 ·
I picked up my Ascent (Abyss Touring) about a week ago. There are approximately 800 miles on the odometer.

I've noticed that at high-speed (70mph+) I am detecting a subtle, fast vibration that is accompanied by a low-pitched drone. My immediate reaction was to have the alignment and wheel balance checked. The front toe was slightly off and both driver's side wheels needed a 10g weight to balance out. I also adjusted the cold air pressure to 33psi. I thought I had finally solved my problem.

Last night I decided to put it to the test and went for a drive across a variety of surfaces while varying my speed as much as possible. Unfortunately the vibration persists. It seems to happen most often when the engine is at 1500-2000RPM. Increasing the RPM seems to mitigate the problem although I have felt it at 2100+RPM. I wonder if I'm feeling the engine being lugged a little? Keep in mind this is a very subtle vibration. If staring at the steering wheel, it is not visible.

I've also noticed this to be most prominent on concrete road decks; especially those just completed near my home. Could it be that I'm just getting more feedback in the wheel than I'm used to? I have experienced this on smoother roads as well though.

Lastly, this might just be a perception thing. My last two cars were V8 and V6 respectively. The latter was so smooth it was almost undetectable when running. I don't mind the little boxer in the Ascent but compared to previous vehicles, it is not as quiet or smooth.

Also my last car had 40-series tires on 19in wheels and I don't recall there being as much feedback in the steering wheel.

Has anyone else experienced this?
my new 2020 does it and it’s driving me crazy, especially because my former 2019 didn’t. Initially I didn’t notice it much in Oregon where I seldom drive above 65, my time in Montana and Idaho at 80 MPH has been obnoxious.

I took it into a tire center and had them rotated and balanced and the tech mentioned that he thought the car sat and had developed slight flat spots. This could very well be the case because the car was built in Jan and purchased in June, with only a few miles on it. It probably sat for quite a while on the lot during the Covid shutdown. They said I should see it subside with time, but it’s been 4000 miles! I’m taking it back to the dealer tomorrow.

like OP said,you can’t see it in the steering wheel but it’s still an unpleasant ride — my seat and floor boards buzz and I hear a noticeable rumble beginning at 70 MPH.

Car tracks perfectly and tires are at 33 PSI. Dealer told me to inflate to over 40 and drive for a while... has anyone tried that? Is it possible that the tires are wrecked?
 
#7 ·
Regarding the sound, I understand that Subaru has refined these engines over time, so that they're not quite as burbly as an older STI often sounds, but there's still quite a "boom" to this engine running (in terms of resonance or sound frequency or something). We have a room over our garage that we use as an office. When my wife starts the Acura MDX (3.5L V-6), I really can't even hear it directly below me. I hear the sound of the starter motor and the engine cranking but, once running, it's basically silent. The Ascent, on the other hand...there's a booming noise throughout the garage and the entire office after that thing starts. Although obviously refined since, that fundamental boxer DNA still lives within! (To be sure, much of this is due to the fact that the engine immediately revs to, and then sits at, about 1,800 rpm when cold...once warmed up, it all seems much more subdued.)

I generally like the background hum of 4-cylinder engines. It's somehow reassuring -- like the little guy is still there and eager to please. Sixs and eights seem much more "aloof" to me, if that makes any sense. Almost like you have to check to see if they're still alive. But 4-cylinders often come with the shakes that an inherently imbalanced engine will produce. The boxer seems to strike a perfect balance for me, pun intended. I still get a little bit of that 4-cylinder "hum", but it's glass smooth in terms of idle and running characteristics. I get the hum without the shakes.

Regarding the tires and balance, ours has been glass smooth so far. I'm quite pleased with the way it drives. I almost hesitate to even rotate the tires, because there's always the potential to set something aflutter when you start moving components around. I feel for those with vibrations -- I'm pretty sensitive to that stuff and it drives me up the wall.
 
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