what is this temporar rattling/vibration/metallic noise when shifting to higher gear?

[francesconyc]

here is a video:
https://youtu.be/RqAahyPrDkM (please listen carefully, the sounds is very subtle.

I recorded this video because I noticed a noise almost as soon as I got the car and I'm trying to identify where is coming from.
it happens only when I press the gas and I shift from 2>3rd or 3>4th
then it goes away when i reach a steady speed

it never happens at idle, neither at 1 or 2 gear.
I can't remember if it happens at lower RPM, but it goes away after a while so i never heard it at 5th gear.

it feels a lot like some parts resonate with the rest of the car until it reaches the same frequency

the sound doesn't feel coming from the engine which seems smooth to me. feels more like a gear/tranny/or exhaust thing...

thoughts?

[pmax]

Have you popped the lower valve covers ?

[john walker's workshop]

G50s rattle at times, normal. What year is your car?

[francesconyc]

1982 911SC
I dont thinks are the valves, the sound is not coming from the back, but more from the "center"..i know it;s vague...

I actually noticed that when it rattles, if I press the clutch it stops the noise... i guess is just a 42 yr old transmission then...

I'll come back with some better audio recording...