Nikon 28-105mm lens works okay but the focus feels "gritty" as if there is a little bit of sand in the gears. My concern is that it is on the verge of breaking and becoming unusable. Is the focus mechanism easy to take apart and repair?

Sounds like while you were fixing it, you crossed a thread somewhere. For the focus to be out on both manual and auto is a give in. All it takes is the finest spec of sand or... bogey to get wrapped up in the threads...and it's night nurse. You can try putting it in Manual Focus Mode, rotating the lens slowly till you hear or feel resistence...then you'll get a better idea of where you're at. If there's resistance, it's crossed - if there's a gritty sound, a piece of sand or snot is throwing out the barrels.

Basically that will be extremely expensive, and probably not worth it. Resign yourself to the fact that the camera is fubar, and replace it with a newer model. Remember NOT to get sand in this one.

Hi,af motor or its gears locked for a small particle (sand grain i.e.).Need cleaning.
Greethings

Lens probably does not extend or retract because the sand got stuck in gear box. The lens can in about 50% of the cases be repaired without having to replace it by opening it and cleaning it out. Try to return to manufacturer first. If you're out of warranty, there are third party places that fix them such as camera lens repairs. If you want to do it yourself, there are also free camera repair guide websites that show you how to replace the lens, the replacement part is usually available on ebay. Opening an cleaning requires special equpiment, but you can just replace the whole lens, it's usually a $30 part.

hi, if you can open your camera and remove the lens unit assy(just be carefull to the flat cable its easy to be broken) you can clean by yourself just to remove the sand goes inside of the lens unit and also to the gear.make it sure you need to use magnifying glass to see the small pc of sand .some time the sand goes to the gear that cause of malfunction or not rotate properly and also the focus gear have also sand that why the focus is bad.if you can't do this just bring to service center and request for cleaning.

thank you

Hi!
It's focus system problem - most likely stuck. Could be sand or some dirt inside focus gears. They're very small for these lens which are used in many Nikon, Olympus, Casio and other cameras so even one small piece of sand can block the focus system. The only way to fix it to take the camera and lens apart and clean it.

Sorry for the bad news. I repair cameras every day and you can trust me - I know what I'm talking about.

Tom

Hi!
It could be focus system problem - most likely stuck. Could be sand or some dirt inside focus gears. They're very small for these lens which are used in many Nikon, Olympus, Casio and other cameras so even one small piece of sand can block the focus system. The only way to fix it to take the camera and lens apart and clean it. 

Sorry for the bad news. I repair cameras every day and you can trust me - I know what I'm talking about.

Tom

Hi!
Most likely the focus is stuck. Could be sand or some dirt inside focus gears. They're very small for these lens which are used in many Nikon, Olympus, Casio and other cameras so even one small piece of sand can block the focus system. The only way to fix it to take the camera and lens apart and clean it. 

Sorry for the bad news. I repair cameras every day and you can trust me - I know what I'm talking about.

Tom

If the sand is in the zoom gears or auto focus gears then the camera would need to be disassembled to remove. Nice thing about this camera is that no soldering is required to take apart. A few small screwdrivers, and some tweezers would be all that is required. Canned air and a needle might also be helpful for removing the sand. If the camera just buzzes then I would say that the sand is in the auto focus gears (the stepper motor will buzz). If the auto focus lens is not fully retracted then the camera lens will not go back in (to prevent the auto focus lens from bumping against the shutter assembly)

A piece of sand had worked it's way into your lens machinery. Replace the whole lens, or find the grain of sand in a gear somewhere.