I've setup a simple translucent conf like described here http://www.openldap.org/doc/admin24/overlays.html#Translucent Proxy , on a Debian squeeze, 2.4.23 server.
lastmod         off
overlay         translucent
translucent_local telephoneNumber3,gidNumber
uri             "ldap://master.example.com"
acl-bind        binddn="cn=manager,dc=example,dc=com" credentials="{SHA}ABC123"


I can overridde (gidNumber) or add attributes(telephoneNumber3):
$ cat add.ldif
dn: uid=bob,ou=people,dc=example,dc=com
gidNumber: 00000
telephoneNumber3: 0000000
$ ldapadd  -H ldap://proxy.example.com -x -W -D 'cn=Manager,dc=example,dc=com' -f add.ldif
adding new entry "uid=bob,ou=people,dc=example,dc=com"

A query on translucent server retrieve remote and local attribute:
$ ldapsearch -LLL -H ldap://proxy.example.com -x -b "ou=people,dc=example, dc=com" '(uid=bob)'
dn: uid=bob,ou=people,dc=example,dc=com
...
gidNumber: 00000
telephoneNumber: 1111111
telephoneNumber3: 0000000

But searches against locally added or overridden attributes fail:
$ ldapsearch -LLL -H ldap://proxy.example.com -x -b "ou=people,dc=example, dc=com" '(gidNumber=00000)'
$ ldapsearch -LLL -H ldap://proxy.example.com -x -b "ou=people,dc=example, dc=com" '(telephoneNumber3=0000000)'

thank you for your help