problems with large objects dump

Our production database, postgres 8.4 has an approximate size of 200 GB,
most of the data are large objects (174 GB), until a few months ago we used
pg_dump to perform backups, took about 3-4 hours to perform all the
process. Some time ago the process became interminable, take one or two
days to process, we noticed that the decay process considerably to startup
backup of large object, so we had to opt for physical backups.

We perform various tests on similar servers with the same version and
postgres 9.2 and it is exactly the same, the database does not have other
problems, nor has performance problems during everyday use.

Could someone suggest a solution? thanks

Sergio