T440s stick/touchpad not working

[ssd_thinkpad]

After booting fresh windows 8.1 my touchpad/sticks works for a half minute, then both are unresponsive.

My usb mouse always works.

I replaced my keyboard bit the problem remains.

What part should i replace?

[rkawakami]

If the system used to work properly before Windows 8 was loaded, then I think that points to a software/driver issue. If, on the other hand, you did not use the T440 before Win8.1, then I would try another operating system, be it Windows (7 or XP) or Linux or even a DOS program that uses a mouse. If they work there, that would tend to eliminate the hardware.

[ssd_thinkpad]

The problem is the hardware.

I wanted to have an idea what I should replace first. I already replaced the keyboard, but that was not the issue. The stick still does not work after a few seconds, and the touchpad also does not work after a few seconds of usage.

[RealBlackStuff]

To be absolutely sure, boot from a Linux Live CD (such as from http://www.linuxmint.com/) and check if they work there.
If yes, blame W8.