Loud sound from Volvo XC70 transmission

I heard much louder sound from my 2001 Volvo XC70 transmission while it’s idling. However, the loud sound disappeared when I shifted to N(neutral)position under same idling situation. What may cause the big difference and does it suggest serious problem in my transmission? Thanks

You mean the sound is louder when the transmission is engaged then when in neutral?

Can you be a little more specific about what the sound is like?

Scratching? Rubbing? Rattling? Swishing? Grinding?

Sound only there when vehicle is moving or stopped?

When the transmission is in gear and you accelerate, the the sound increase (like a rotating sound) or change pitch? (Higher/lower)

I only hear this grinding sound from the transmission when the car is stopped and transmission engaged in D drive. The sound is gone when it’s in Neutral Drive.There is no sound coming out when the car is moving. Thanks

Volvo has a couple of heat shields on parts underneath the car. One of the shields may be loose and is vibrating more when the car is in drive. Should be easy to check and easy to fix. First check the shields on the catalytic converter(s).

If it is the transmission, not so easy and not cheap to fix.

Yes, have the shields checked and if they are not the source of the ‘grinding’ noise, get a couple more (independent) opinions/estimates.

The noise MAY not be coming from the trans.