Here is the parts breakdown.
Replacement parts for FRIGIDAIRE LER331DS0 Frigidaire/dryer | AppliancePartsPros.comThis is difficult to be of much help without actually being there,
If you click on the pictures of the parts then often a new image with more views or an expanded view will open. This may help you see what the new parts should look like.
Try running the unit disconnected from the vent, this may reduce the echo in the unit and help narrow down what is causing the racket.
You will have to remove the drum and check for wear etc.
One thing to note is that when you remove the clip (Item 6 in Section 1) from the back of the unit be careful as the ball bearing (Item 5 in Section 1) likes to jump our and then play hide and seek. So you end up spending an hour looking for it.
Check the rear drum support/bearing for wear. Clean it out and re-lube it. When reassembling be sure to use a high temp grease (NI at the end of Section 1) to re-lube it.
Normally these start squeaking/screeching when they need lube or are worn.
Check the front felt seals for wear (Items 20 and 21 in Section 2). Also where they ride.
Check that there is nothing between the drum and the machine. Bra wires are notorious for this though usually it is a scraping noise,.
Check that there is not too much slop in the idler wheel bearing.
Spin the motor to see if there is any wobble or indication of bearing slop.
Also look at the blower wheel to see if there is wobble there.
From the parts it looks like your blower wheel is screwed onto the motor shaft. This is probably a left hand thread.
Sorry I can not be of more help but this type of problem can be a bear at the best of times.
