There are lots of train and transportation preschool songs here (click).

This page (click) has an interesting variation:

Little Red Caboose

Sing in normal voice:
Little red caboose,
Chug, chug, chug
Little red caboose,
Chug, chug, chug
Little red caboose
Behind the train, train, train, train
Coming around the track, track, track, track
Smokestack on its back, back, back, back
Little red caboose
Behind the train, choo! Choo

Sing in deep voice:
Great big caboose,
Chug, chug, chug
Great big caboose,
Chug, chug, chug
Great big caboose
Behind the train, train, train, train
Coming around the track, track, track, track
Smokestack on its back, back, back, back
Great big caboose
Behind the train, choo! Choo!

Sing in high-pitched voice:
Teeny tiny caboose,
 Chug, chug, chug
Teeny tiny caboose,
Chug, chug, chug
Teeny tiny caboose
Behind the train, train, train, train
Coming around the track, track, track, track
Smokestack on its back, back, back, back
Teeny tiny caboose
Behind the train, choo! Choo!

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This Google Search (click) may help you find more information, but this is a song that has been posted countless times on the Internet. At the Harry Fox Agency the only copyright I can find is the Sweet Honey in the Rock/Bernice Reagon Johnson arrangement (copyright covers just the arrangement). There is one Silver Burdett school songbook from 1956 that has a song with that title, but I don't have that book - I've contacted a Mudcatter who does have it, but he's probably wise enough to be asleep right now...
My hunch is that this song is more recent than 1923, the cutoff date for U.S. copyrights; but it's so common that it will be very difficult for anyone to prove a copyright claim.
-Joe-