Yes i would start looking at the inside and outside[HUBS] as us old-timers called them.
Wash the fans with floor stripper,get inside the vanes,make sure the fans are balanced,put a srewdriver through the center hole[a long shaft phillips head]and spin the fans with the blower of any vacuum.This will tell you if there out of balance............
 
  O.T.

Hi Dan, spray the fan case at the seam between the lower and upper fan case,WD40 works fine,then take a flat head screwdriver and put it at the seam the one that the screws go through,tap the screw driver with a ball peen hamer around the edge of the case,it will take some time but you should be able to knock the housing off,there is usually rust on the inside of the lower fan case.Another way is to heat the housing with a torch, get it just hot enough so the cases start to loosn and then take the screwdriver and hammer and bang around the edges again.
 
If you hurt the housings these are still around at most good vacshops,either new or used.
 
you can do it...........
 
  O.T.

Dan,
  The groan you heard in my figuring is the front bearing. The reason I suspect it is one the age. After that many years of time the grease has dried. The bearing is a sealed bearing so there is no greasing it but replace it.  
What you called the arbor is the armature. Watch not to  get anything on the armature. To go further into the motor is simple. A phillips screwdriver is required . After removing  the spacer that is under your fans, you will see  three screws that hold the stationary fan. This is  also the bearing plate. Once you take those three screws out and pull the bearing plate free from the rest of the motor you can remove your armature. Before you remove your armature check and see if there is any play at the other end. This is a bronze bearing. I will guide you thru oiling it later.
   You will find that to work on this machine you need an 11/32 socket, phillips screwdriver, a couple of flat screwdrivers, a drill, drill bit to remove the bearing cover and screws and nuts to replace bearing cover. Three in one oil to oil bronze bearing.
 Before you go to far private message me and I will see what I have that I can e-mail you to help you.

Howdy,
 
I want to thank everyone for their help in rebulding the Olympia One. It's been great therapy for me. I let my son put the motor fans back together. We couldn't have done it without the advice of the experts.
 
No more groan when the machine starts up or turns off.  She's sounds nice and smooth. Now I just have to wait for my PN4 bearings, belt and brush roll.
 
I vacuumed my rec room quickly with a PN6 and the Olympia did a great job.  
It's true...nothing sucks like an Electrolux.
 
old-timer
tiger21
vernon
 
Thank you again!
 
Dan