Why is my transaction log file growing so large after disabling replication?
From your comment, you apparently had success re-enabling replication, and then removing it properly using the information contained in the post entitled Disable Publishing and Distribution.  

To summarize the steps involved:


Create a new publication with only one article (which we are about to delete anyway). When prompted for a schedule for the snapshot agent, choose any time that is not right now.
Stop all replication-related jobs. For a list of job names, see the
"Agent Security Under SQL Server Agent" section of Replication Agent Security Model.
At each Subscriber on the subscription database, execute sp_removedbreplication to remove replication objects from the database. This stored procedure will not remove replication jobs at the Distributor.
At the Publisher on the publication database, execute sp_removedbreplication to remove replication objects from the database.
If the Publisher uses a remote Distributor, execute sp_dropdistributor.
At the Distributor, execute sp_dropdistpublisher. This stored procedure should be run once for each Publisher registered at the Distributor.
At the Distributor, execute sp_dropdistributiondb to delete the distribution database. This stored procedure should be run once for each distribution database at the Distributor. This also removes any Queue Reader Agent jobs associated with the distribution database.
At the Distributor, execute sp_dropdistributor to remove the Distributor designation from the server.



  NOTE:
  
  If all replication publishing and distribution objects are not dropped
  before you execute sp_dropdistpublisher and sp_dropdistributor, these
  procedures will return an error. To drop all replication-related
  objects when a Publisher or Distributor is dropped, the @no_checks
  parameter must be set to 1. If a Publisher or Distributor is offline
  or unreachable, the @ignore_distributor parameter can be set to 1 so
  that they can be dropped; however, any publishing and distributing
  objects left behind must be removed manually.