Replacement ball bearing for bottom of 3927 postwar track cleaning car?

The ball bearing is part number 3927-14, the correct washer is # 011-24.  I didn't check if the parts were available, but I suggest you look up Olsen's Toy Train Parts website.  That site has a "Library" section, which are pages and pages from Lionel repair manuals, showing part numbers, if you need them.  Then you may have to try different vendors for the right part.  I only say that as some parts are getting scarce, and aren't being reproduced, and not all vendors will have everything at a given time.

The ball bearing is available at Trainz.com, $.98 for two. 

Thanks, guys! Is this a great forum or what? Olsen's and Trainz don't have a washer, but I have a small one in use already that seems to space the armature from the brush plate correctly, and it isn't a "thrust washer" since the gears are straight cut and not helical---should be OK. 
Will order ball bearings from Trainz-thanks again.

Don

The 3927-14 ball bearing is  .156 dia. ball bearing ( 5/32 ).

John

Thanks John!

Good to know.

For what it would cost (with shipping) to purchase a couple of balls, you can probably buy a lot of 100, and have enough to supply all your friends. Here is one.

Thanks for link to "Tool Supply" eBay store: many balls for bearing and some brass w/tapped holes, etc.  Already did what you said: bought 2 pkg of 2 ea from Trainz at about $11 incl shipping.  100 from Tool Supply is only $7 incl shipping!

Their store will come in handy another time, though.