Honda City 2021 5th generation, Hissing sound on low gears

[pwuser165182159546]

I have Honda city 2021 model, it's only 68000km driven
It gives hissing sound with A/C and without A/C usually on low gears, on high speeds, this weird sound doesn't come.
Please let me know, I have checked to a mechanic, He said it comes from Gearbox, need to open gearbox to check this sound.

Please i need experts to answer my problem.

[pwuser165182159546]

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[pwuser166331039855]

from which city you are?

next time when visit mechanic, don't tell him about gear. Just tell him to check the vacuum connections because you hear air-hissing sound. And let him trace if all its vacuum connections are working fine.

apart from this, any other abnormality you observe while driving ? Like if it struggles to shift gears, or instead of going faster on higher gears, it speeds reduces, etc. etc.

[pwuser165182159546]

it doesn't come on normal speed, when i speed up it comes for some time then fades away.
I have changed the gear oil at 60,000, Mechanic thought it was due to gear oil,
but after changing the oil it still there

[pwuser16229839641]

Any Solution Found of this problem?