I had the same problem with my Maytag Proforma Gas Dryer. I have owned it for 7 years when it decided to make loud squeeling noises while drying. You are right, some WD-40 did the trick.
In my case, there were 2 guide wheels toward the rear of the drum unit. I had to remove the top and front panels and the drum to access them. This results in the removal of the belt. Once the drum is removed you can see the wheels. I sprayed them with a little bit of WD40 and the noise was gone. The heat reacts with the WD40 causing a "rotten-egg" smell. It should go away in time (I hope).
I had to remove about 9 screws to get into the dryer. There was also a tensioner wheel for the belt that was a little tricky to put back. I suggest you look at the assembly carefully before you remove any parts. Good luck.
Rafael J
January 2006