New to iRules and trying to get port translation to work

I've got a virtual server set up like this in my environment, where the client comes in on port 80 (http) but the backend connection is on a different port (we'll say 55555). I have no special setup, and it works for me... My config is similar to the following...

ltm pool MY_POOL {
    load-balancing-mode least-connections-member
    members {
        10.0.0.1:55555 {
            address 10.0.0.1
            session monitor-enabled
            state up
        }
    }
    monitor MY_TCP_MONITOR
}

ltm virtual MY_VS {
    destination 192.168.10.10:http
    ip-protocol tcp
    mask 255.255.255.255
    pool MY_POOL
    profiles {
        http { }
        tcp { }
    }
    source 0.0.0.0/0
    source-address-translation {
        type automap
    }
}

Also, if you turn off the port translation, does it work for you?