A lot of people (including me) are looking for how to fix a stiff zoom ring on the 14-24mm f/2.8 lens. There is no repair manual on the web.
The story behind: After severely dropping my relatively new Nikon AF-S NIKKOR 14-24mm f/2.8G ED I experienced a very(!) stiff zoom ring with a "lock" at about 16mm. But I was lucky not to break any lens, the hood and cap have minor damages. Still Nikon told me it is going to cost me about $ 1000, uff!
The lens is relatively easy to dismantle. There is one danger though: You have to remove the rubber from the zoom ring, remove the little metal shield which is taped on and unscrew the zoom indicator below. Then you can begin to take it apart. You have to remove about 20 screws all in all and one(!) ribbon cable. Please be careful. Have some cleaning wipes (cloth) ready. Grab the "naked" lens with them, do not touch any glass. You'll find a video on youtube that shows how to dismantle the lens. You need some experience, but it is not that hard to do. You want to mark the position of some parts with a pen. The last part is to remove the three slotted screws which hold the front element.
The problem lies within the guidance of the big front element. Please refer to the image I attached. The drop resulted in three little dents (the image shows one) in the outer barrel. The dents are not the problem but the convexities along the inner surface. These you can remove easily with a sharp knife. The barrel is made out of aluminium. The inner barrel probably still moves smoothly.
My lens also suffered some dents on the topmost ring which holds the actual zoom ring. I removed those as well until the zoom ring was moving without greater resistance. A little bit of ball bearing grease helps as well.
The whole procedure took me about an hour. The zoom ring is now moving well again and the "lock" at 16mm is gone. Needless to say I am very happy now. The lens works well again. I just should have done this right away. (The 17-35mm f/2.8 is good but the sharpness of the 14-24mm f/2.8 corner to corner is unbeatable so far).
If you have questions please do not hesitate to ask.