diff --git a/lib/mongo/repl_set_connection.rb b/lib/mongo/repl_set_connection.rb
index 947e3e7..9d9ef21 100644
--- a/lib/mongo/repl_set_connection.rb
+++ b/lib/mongo/repl_set_connection.rb
@@ -16,8 +16,6 @@
 # limitations under the License.
 # ++
 
-require 'sync'
-
 module Mongo
 
   # Instantiates and manages connections to a MongoDB replica set.
@@ -83,8 +81,6 @@ module Mongo
     # @raise [ReplicaSetConnectionError] This is raised if a replica set name is specified and the
     #   driver fails to connect to a replica set with that name.
     def initialize(*args)
-      extend Sync_m
-
       if args.last.is_a?(Hash)
         opts = args.pop
       else
@@ -157,23 +153,21 @@ module Mongo
     # Initiate a connection to the replica set.
     def connect
       log(:info, "Connecting...")
-      sync_synchronize(:EX) do
-        return if @connected
-        manager = PoolManager.new(self, @seeds)
-        manager.connect
+      return if @connected
+      manager = PoolManager.new(self, @seeds)
+      manager.connect
 
-        update_config(manager)
-        initiate_refresh_mode
+      update_config(manager)
+      initiate_refresh_mode
 
-        if @require_primary && self.primary.nil? #TODO: in v2.0, we'll let this be optional and do a lazy connect.
-          close
-          raise ConnectionFailure, "Failed to connect to primary node."
-        elsif self.read_pool.nil?
-          close
-          raise ConnectionFailure, "Failed to connect to any node."
-        else
-          @connected = true
-        end
+      if @require_primary && self.primary.nil? #TODO: in v2.0, we'll let this be optional and do a lazy connect.
+        close
+        raise ConnectionFailure, "Failed to connect to primary node."
+      elsif self.read_pool.nil?
+        close
+        raise ConnectionFailure, "Failed to connect to any node."
+      else
+        @connected = true
       end
     end
 
@@ -208,13 +202,11 @@ module Mongo
     #   occurred. +false+ is returned when unable
     #   to get the refresh lock.
     def hard_refresh!
-      return false if sync_exclusive?
-
       log(:info, "Initiating hard refresh...")
       background_manager = PoolManager.new(self, @seeds)
       background_manager.connect
 
-      # TODO: make sure that connect as succeeded
+      # TODO: make sure that connect has succeeded
       update_config(background_manager)
       initiate_refresh_mode
 
@@ -235,14 +227,14 @@ module Mongo
     #
     # @return [String]
     def host
-      super
+      self.primary_pool.host
     end
 
     # The replica set primary's port.
     #
     # @return [Integer]
     def port
-      super
+      self.primary_pool.port
     end
 
     def nodes
@@ -266,18 +258,15 @@ module Mongo
 
     # Close the connection to the database.
     def close
-      sync_synchronize(:EX) do
-        @connected = false
-        super
+      @connected = false
 
-        if @refresh_thread
-          @refresh_thread.kill
-          @refresh_thread = nil
-        end
-
-        @manager.close if @manager
-        @sockets_to_pools.clear
+      if @refresh_thread
+        @refresh_thread.kill
+        @refresh_thread = nil
       end
+
+      @manager.close if @manager
+      @sockets_to_pools.clear
     end
 
     # If a ConnectionFailure is raised, this method will be called
@@ -301,14 +290,14 @@ module Mongo
     end
 
     def authenticate_pools
-      super
+      self.primary_pool.authenticate_existing
       self.secondary_pools.each do |pool|
         pool.authenticate_existing
       end
     end
 
     def logout_pools(db)
-      super
+      self.primary_pool.logout_existing(db)
       self.secondary_pools.each do |pool|
         pool.logout_existing(db)
       end
@@ -351,16 +340,13 @@ module Mongo
     end
 
     def checkin(socket)
-      sync_synchronize(:SH) do
-        if pool = @sockets_to_pools[socket]
-          pool.checkin(socket)
-        elsif socket
-          begin
-            socket.close
-          rescue IOError
-            log(:info, "Tried to close socket #{socket} but already closed.")
-          end
+      if pool = @sockets_to_pools[socket]
+        pool.checkin(socket)
+        if !@sockets_to_pools[socket]
+          close_socket(socket)
         end
+      elsif socket
+        close_socket(socket)
       end
 
       # Refresh synchronously every @refresh_interval seconds
@@ -372,16 +358,21 @@ module Mongo
       end
     end
 
+    def close_socket(socket)
+      begin
+        socket.close
+      rescue IOError
+        log(:info, "Tried to close socket #{socket} but already closed.")
+      end
+    end
+
     def get_socket_from_pool(pool)
       begin
-        sync_synchronize(:SH) do
-          if pool
-            socket = pool.checkout
-            @sockets_to_pools[socket] = pool
-            socket
-          end
+        if pool
+          socket = pool.checkout
+          @sockets_to_pools[socket] = pool
+          socket
         end
-
       rescue ConnectionFailure => ex
         log(:info, "Failed to checkout from #{pool} with #{ex.class}; #{ex.message}")
         return nil
@@ -463,14 +454,12 @@ module Mongo
     #
     # NOTE: will be available in driver release v2.0.
     def checkout_tagged(tags)
-      sync_synchronize(:SH) do
-        tags.each do |k, v|
-          pool = self.tag_map[{k.to_s => v}]
-          if pool
-            socket = pool.checkout
-            @sockets_to_pools[socket] = pool
-            return socket
-          end
+      tags.each do |k, v|
+        pool = self.tag_map[{k.to_s => v}]
+        if pool
+          socket = pool.checkout
+          @sockets_to_pools[socket] = pool
+          return socket
         end
       end