Looking for Information on Francis Johanis Gehle Prussia 1800

I am doing some research into the Gahley Family Name. Johanis Adolph Gahley was the son of Francis Johanis Gehle born in Prussia. It appears that Johanis Gahley was the only child. I have no further history on the Gehle line and would like to follow it further.
I have been told that the reason for the name change was that it had something to do with choice of religion.
Johanis Adolph Gahley was my Great-Great-Grandfather.
Any help would be appreciated.
Thanks,
Cory Gahley