** the dryer it makes this whirring noise ... Any ideas on what is causing this **
It could be worn drum slides or drum rollers, something caught in the blower fan, the drum rubbing on something, etc.
** is this a warning sign for future problems? **
It's definitely a warning sign that there is a current problem. Whether it could lead to additional problems if continued to be used in that condition is fairly likely, more so depending on the make and model number of the dryer you happen to have.
You can find tips for locating the model and serial number tag on your appliances in the 'Repair Parts' section of my site linked below. It will be required to get the proper replacement parts once you figure out exactly what the cause is.
The Appliance Information Site
[This message has been edited by DanO (edited January 11, 2004).]