Need to also make sure you are getting your parts terminlogy correct on this old one so everyone is on the same page.
This is one of the very old original 2 v-belt Maytag dryer, (Halo of heat with heater in front of drum).
What I would consider the idler pulley on this machine is the big pulley to the lower right hand side looking at the back.
I don't think I've ever seen an idler pulley wear out on one of these, just need to clean up gummed up slide and clean the axle with emory cloth clean old grease from bushing and relube with a thin film 3-n-1 machine oil and lube the slide with auto wheel bearing grease.
A more common problem that I have seen numerous times on these machines is the motor pulley wearing out. It is an aluminum pulley and wears so that it won't grip the belt anymore then won't turn the pulleys.
You're going to be very lucky to find parts for this old Maytag - pretty much belts, t-stats, wiring terminal block and screws are the only things listed as still available on the Sears & APP parts breakdown pages.
Original part# 3-840 subs to newest part# 300840 Idler or Reduction Pulley (no longer available sinse 2009)
Edited by Budget Appliance Repair, Today, 07:40 AM.