http://www.nikonchat.com/nikon-autofocus/

Is the Tamron 28-75mm f/2.8 AF lens for nikon d40x?
Nikon AF lenses that autofocus on the D40 and I was not sure if it was the same third-party lenses:. Also, another question I get the lens or the sigma 24-70 f2.8 macro (without the hsm because it costs too much) this? I mainly want to use Pictures.
The D40x does not have focus motor so for any auto-focus lens that the lens must have a motor. designated AF lenses Nikon AF-S or-I were designed for Nikon digital SLRs lack a focus motor in the camera body. Tamron Model AF09NII-700, 28-75mm f2.8 XR Di LD ASPH (IF) has incorporated a motor for auto focus with your D40x. $ 399.95 at B & H-S DX Zoom-Nikkor 12-24mm IF-ED AF f4G $ 899.95 at B & H. AF-S DX Zoom-Nikkor ED 14-24mm F2.8G $ 1749.95 at B & H. http://www.bhphotovideo.com
Nikon SWM Autofocus Motor