If your monthly pension $3845 not from social security - it will likely be fully taxable.
If you do not want any tax withheld from your pension in 2008 - you need to file the form W4-P - http://www.irs.gov/pub/irs-pdf/fw4p.pdf with the administrator of your pension fund. if you do not want any federal income tax withheld - check the box on the line 1.
Here is a similar form for CA - http://www.edd.ca.gov/pdf_pub_ctr/de4p.pdf
Assuming that will be your only income $3845 * 12= $46140 - that will be taxable and you need to file a new withholding certificates in 2009 or pay estimated taxes on your own.