Nikor af autofocus loose rattle - Nikon Nikkor 18-55mm f/3.5-5.6G ED AF-S DX (silver) Lens

No Nikon lens ever zooms automatically, so I assume you mean focus.
The D5100 lacks an autofocus motor, requiring the lens to have one. The older 70-300mm lenses lack this motor, expecting the camera body to have one.
The D5100 will only autofocus with lenses designated AF-S or AF-I. It will not autofocus with older AF-D and AF-G lenses.

Every one (assuming the camera supports autofocus in the first place, of course--old film Nikons didn't). The lens has an autofocus motor, so the camera doesn't need one.

Film Nikons supported autofocus starting with the N2000. (Actually, the F3 also had autofocus capabilities, but used a different system). All the digitals support autofocus.

Sorry, but the D40x lacks an autofocus motor, depending on the lens to have one. Nikon calls such lenses AF-S. This particular lens does not have such a motor, relying on the camera to have one. The only 50mm lens currently available with an autofocus motor is this one:
http://www.nikonusa.com/Nikon-Products/Product/Camera-Lenses/2180/AF-S-NIKKOR-50mm-f%252F1.4G.html

Earlier this week the Nikon web site listed a new 50mm F1.8 lens with an autofocus motor, but then it was removed. Hopefully they will officially announce this lens soon.

You're welcome. Glad to be of service.

Pull the lens all the way IN (i.e. zoom to 70mm) then press the MACRO LOCK, and then adjust focus using the macro ring.

Hi,
The manual can be found on Nikon's website or click on the following link: http://www.nikonusa.com/pdf/manuals/lenses/AF/AFSVR70-200_2.8G_(80)05.pdf
The manual is a combination of several languages all bundled together. The English portion is from P14 - P21.
Hope this helps.
Andrew

visit linkdelight Photography Accessories

Make sure the AF/MF mode button on the lens is set to AF.
What focusing mode do you have selected in the camera? Single Shot, AI focus or AI Servo? 
If Custom Function "C.Fn IV -1 Shutter button/AF-ON button" is set to option 2 or 3, the AF will start when you press the AF-ON button.
I hope this help you!
/Chris

Send it in. Don't even think of trying to fix it yourself. Once you start to disassemble the lens, you will find it impossible to reassemble it yourself. Lenses are often designed so that following the order of disassembly in reverse will not work on reassembly. It is allot cheaper to pay for the repair of your problem then to pay to reassemble a collection of parts.

http://support.nikontech.com/app/answers/detail/a_id/14439