Walcker or Walker Family History

Pre-USA immigration, my family spelled their surname Walcker.  My great grandfather kept the Walcker spelling, but my grandfather shortened it to Walker. I feel fairly certain, it was an attempt to
Americanize the name
 
My Walcker's left Germany about 1816 and settled in Neu Freudenthal, Russia.
The Karl Stumpp book, mentions them (page 474) as coming from Steinheim/Marbach, Württemberg, Germany.  I am currently extracting my Walckers from LDS film  # 1187118 and #1187119 for that town.  So far, I've been able to find them  back to the mid-1700's, but I still have more films to look at.  The bulk of my
Walcker's were civic minded and participated in town government.  They were also butchers and rope makers by trade.  The Steinheim records show that my paternal 3rd great grandparents, Samuel Friederich Walcker b. 1770 and Anna Maria Christiana Pfleiderer b. 1782, emigrated  to Russia in 1817 with their children.  Samuel Friederich went by the name of Friederich Walcker.  Steinheim/Marbach was part of the  Ludwigsburg District.  There were a total of 38 families from Marbach who emigrated to Russia