4GB (1X4GB) Memory Ram Compatible with Lenovo Thinkpad T400 2766 By CMS A34 - Computer Memory Solutions
8GB (4GBx2) Team High Performance Memory RAM Upgrade For Lenovo ThinkPad T400 Series T410 Series Laptop. The Memory Kit comes with Life Time Warranty. at Amazon.com
Have ThinkPads gotten worse over the last decade? – A ThinkPad retrospective - NotebookCheck.net News
SOLVED: Are 16GB RAM (2x8Gb) possible on my Lenovo T400? - Lenovo Laptop T400 - iFixit