John,
I work on everything from HOn30 to Fn3, brass, Flyer, Bachmann; everything except Lionel...
Lionel engines have never been discussed in the 20 year history of the RnR lists.
It's like separate hobbies; Lionel and everything else.
PFM Shays are among the easiest HO brass locos to work on.
The one major issue with PFM Shays is that many have a brass upper worm which wears prematurely.
Some PFM Shays have steel worms which is much preferable. NWSL, which is closing soon,
made steel replacement worms for brass worms in PFM geared locos. Mark, a repair person
with Caboose, doesn't expect the NWSL parts to be available once they close shop.
My advice would be to not delay in having it checked.
Non PFM shays like Bachmann, Key, OMI also had gear issues, NWSL had produced repair kits for some
of these models as the importers did not maintain spare parts inventories after the production runs sold out.
ken clark