Distribution--cleanup Job not cleaning properly - Distribution DB is growing fast

Hi All,
Can anyone help me to solve the below issue on replication cleanup job..
Problem : Distribution Cleanup Job running for a long time[2 hrs] and it is not cleaning published old transactions in the distribution DB eventhough it is completing successfully. The cleanup job also blocking the distribution agents to apply the replicated commands[sync - Publisher - Subscriber] whle the job is running.
The MSrepl_Commands table is growing 2-3 GB everyday and it is keep growing since the Distribution cleanup job is not cleaning properly.
I tried to shrink the Distribution DB and it doesnt help...
Is there any way where we can figure out or solve the issue without affecting the current replication setup? or is there any way to delete the old transactions on the distribution db manually...
Aby help would be really appreciated....
Thanks
Gobira

http://www.mssqltips.com/tip.asp?tip=1823

You can reduce the retention period if it is too high...
If you know all the transactions distributed to all subscriber then you can clean the table using DELETE statement...