I have a 9 year old Rheem Criterion (upflow RGDJ) furnace that makes a short noise once the main blower starts. It's only last for a second, a wobbling noise that goes away once the blower is fully started. Since it doesn't have a belt, is there something that can where out that would cause this noise?:confused:

It may just be a blower wheel out of balance from being dirty. Worst case the hub or fins are separating from the blower wheel. Check to see if you see small metal filings inside the blower wheel around the blower shaft and at the point where the fins attach to the wheel. Its only going to get worse as time goes on and it will come apart on you leaving you with out heat or air.