Pneumatic hissing noise when shifting

[Cat4]

I’ve noticed a pneumatic/hissing/scratchy noise, almost sounds like a turbo blow off, about a second before my Jeep shifts from 1st to 2nd. Typically happens when the Jeep is hot and starting from a stop and medium throttle. I don’t think it happens when I accelerate hard but not sure as it may get drowned out by the engine. Doesn’t happen all the time. 3.6 etorque, auto. I had the same issue on my 2020 JT which was ultimately a lemon for other reasons. Any thoughts?

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[mwilk012]

Are you sure you aren't hearing the vacuum pump/brake booster?

 

[jessedacri]

I think you might be hearing the same thing I posted about a while back:
https://www.jlwranglerforums.com/fo...or-whine-noise-accelerating-in-1st-2nd.43165/

If you listen to this TrailRecon video at the 10:15 mark you can hear what I'm describing faintly as the yellow Jeep goes by:

Is this it? If so, I've never found an explanation other than it's normal for the 850RE transmission and most people just aren't hearing it, I guess.

 

[Cat4]

Are you sure you aren't hearing the vacuum pump/brake booster?

Don’t believe so as the noise is not tied to the brakes at all, but could be wrong. I thought brake booster noise happened when you hit the brake.

 

[Cat4]

I think you might be hearing the same thing I posted about a while back:
https://www.jlwranglerforums.com/fo...or-whine-noise-accelerating-in-1st-2nd.43165/

If you listen to this TrailRecon video at the 10:15 mark you can hear what I'm describing faintly as the yellow Jeep goes by:

Is this it? If so, I've never found an explanation other than it's normal for the 850RE transmission and most people just aren't hearing it, I guess.

Hard to tell from the video but I wouldn’t describe it as a whine. It’s a single event, almost like releasing air from a pressurized tank. Lasts about a second and just before it shifts.

 

[mwilk012]

Would you recognize the sound of the vacuum pump if that is what it was?

 

[Cat4]

Would you recognize the sound of the vacuum pump if that is what it was?

Probably not haha is there a way to verify?

 

[mwilk012]

Yea, sit there with the windows down in park and press the brakes a few times. Listen to the hiss when it kicks on.

 

[Cat4]

Yea, sit there with the windows down in park and press the brakes a few times. Listen to the hiss when it kicks on.

Confirmed, not the brake booster…

 

[Cat4]

Bump. Any thoughts?

 

[UniqueUserName]

Could it be the electric motor bridging the shift?

 

[Cat4]

Could it be the electric motor bridging the shift?

Maybe, however I had a 2020 JT without eTorque and it did the same thing.

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