I had first installed this Intel 7260AC card in my old Lenovo 300 N100. When that died, some of its internals, including this WiFi card, moved to the T400 I got on Ebay. The card served me well for a while through Windows 8 and 10 upgrades, different router + OpenWRT combinations etc. But, recently, with drivers no longer being updated, I started noticing issues. The card would frequently go into fits, repeatedly appearing and disappearing in device manager, causing me all sorts of annoyances. Given that the T400 can only use mini PCIe cards, I was not hopeful that I could find a decent replacement.
Eventually, I did decide to take a chance on something called “MPE-AX3000H Dual Band WiFi 6 Card 802.11ax Wireless Half Mini PCI-E WiFi Card” on Amazon. I am glad I did.
Given that I lose a screw or two every time I open this laptop, I decided to do also go ahead and put the T9900 that I had picked up at a very decent price on Ebay some months ago. In addition, I had been meaning to put in a new BIOS battery given that the original was about 13 years old at this point.
All went really well. I am using the latest drivers from Intel for the WiFi card, the laptop immediately recognized the new CPU, and weird BIOS issues at boot time are gone. These were all shots in the dark, but they worked :-)