I've been commuting locally around town in my Novara REI IGH (SHIMANO 7speed). One day I decided to carry a heavy load (around 20-25 pounds on my pannier rack and I had to jump off the curb due to an emergency. My bike pounded the pavement hard from jumping off the curb. Next, I started hearing a low grinding noise from the IGH. I ignored the noise and three days later, the grinding noise became louder and louder. I stopped riding this bike and switched off to my fixed gear. Anyone who has a IGH experienced such a noise from the IGH? What can be wrong with it since I can see the gears inside from my naked eye. Please help!

Sounds like you might have stripped a gear... if you're adventurous, you could try opening it and seeing, but chances are it will need to be repaired. Does it make the sound in every gear, or just in certain ones? If it's only in certain ones, then it's very likely a messed up gear. Shift it into your 1:1 gear (should be 4th on that hub) and see if it still is grinding.

Oftentimes frame flex or even a little tug at the shifter cable can cause the gearing calibration to get off. Then, you'll hear grinding in some gears. So, whenever the Shimano IGH gears get a little crunchy, always check that your gearing calibration is okay. If you don't know what this means, then check out: https://www.sheldonbrown.com/nexus-mech.html

Hopefully, this is the problem and not something major. Good luck!

Do you mean that you can actually see the gears from outside the case? If so, I'm guessing you have broken the axle, and the hub case is spreading apart. Not sure, as have not worked on these. Anyway, if you can see the gears, you have at least a rebuild if not a replacement in your future.

I suspect the OP dropped a 't on the can...

If he CAN see the gears inside - please take a picture! This would indeed be an interesting hub...

**** I had a typo. I meant I CAN'T see the IGH from the outside. The grinding noise is not from shifting. It's just from basic peddling .

First try adjusting the cable tension. Shift into whichever gear is highlighted in red on the shifter window. Then, clean off the little clear plastic window on the hub down near the dropout. You'll see two little marks, which should line up. (If your hub is older, it may have two little metal fingers instead of marks inside a plastic window.) Twist the threaded adjusting barrel of the shifter cable, usually located on the shift lever, until the two marks line up.
If your grinding is still there after the adjustment, then you'll need to think about having the hub itself serviced.

There's actually not a 1:1 on a Nexus 7; every ratio is created through one or two planetaries.

tcs

Fourth gear (or whichever one is highlighted on the shifter window) is the gear at which you actually get whatever your chainring/rear cog combination is. That is the 1:1 gear from which adjustments are made.

accurate.

Also you should check for cracks in the frame... I've busted them at the dropout end of the chainstay, and now at the BB end of the chainstay/seat tube. It made it's odd noise when I was pedaling, or any time the frame flex'd.