cause of noise?

[73Charger]

What could cause a noise when backing up and it only seems to happen when I first back the cold car out of the portable garage after sitting a while?  Is this something in the tranny hanging up or brakes?  its kind of a loud sound like a vibration. its an automatic 904

[RD]

could you do a better job at describing the sound please?

scratching
whirring
screeching
knocking
tapping
clicking
humming

i am being serious mind you.

[73Charger]

its not a: scratch,schrech, knock, tap, click.  the others are closer - its a lower pitched sound - constant the first few seconds I back up.  I usually stop then, sticking it in neutral, then go back to reverse and it usually goes away. sometimes it makes it longer if I don't stop.
This is after the car has sat for weeks in my portable garage so it is exposed to heat, and some water on the dirt floor.  I dont think it makes it once warmed up though. I just replaced my emergency brake cables - cept one side which appears to be working
low pitched buzzing rattle?

[dodge freak]

A mopar trans -auto- should be started or at least run in neutral for 20-30 seconds before putting it in gear. In park no fluid flows thought most of the trans. GM and Fords do, this is why you always check the level in neutral. Try that next time and see if it goes away.

[NHCharger]

A mopar trans -auto- should be started or at least run in neutral for 20-30 seconds before putting it in gear. In park no fluid flows thought most of the trans. GM and Fords do, this is why you always check the level in neutral. Try that next time and see if it goes away.

I was told the reason for this noise  is the torque converter takes a minute to get lubed up and the tranny should be in neutral for this. So I agree with dodge freak on this.