Are you located in Canada?
I can find some info on PBXR series (indicates they are commercial grade units) although none on your specific Model Number.
Mabe Canada handles parts for GE. Unfortunately their web site stinks for getting any real info.
So if you have to get parts from them make sure you have the part in your hand when you go there, it is the only way to ensure you get the correct item. Also often they can just look at a part and match it.

You will have to open it up and find the cause.
Many units have plastic glides at the front to support the drum, perhaps they are worn.
Often though where the noise is coming from can be deceiving, so it could be almost any part. If not the glides then next would be the idler wheel or rear support rollers.
I would check out all the moving parts or anything that has a moving part rubbing on it. Also check the belt and drum seals. Replace as necessary.
Give the interior a good clean and check/clean your vent system.

The following site has some good info
http://www.applianceaid.com/dryers.html