Does it sew okay on a single or double layer as this sounds like the threading up is not correct to me. The grinding may be that the bobbin case isn't in correctly.
However, best way to diagnose is to start fresh, take off the thread, remove the bobbin case, clean out the rotary hook (under the needle plate) clean the feed dogs and remove the needle. Clean the tension discs too (turn to zero and floss between the metal discs with selvage edge of a clean piece of cotton scrap fabric, until its clean, no gunk coming out). Turn tension dial back to 4 or 5, your normal setting.
Now wind a fresh bobbin making sure it winds nice and smoothly, keep tension onto the thread spool to achieve this and watch as the thread goes onto the bobbin, give it a nudge so it fills the bobbin smoothly across the whole core, top, middle and bottom.
Now put bobbin into bobbin case and ensure it goes into the tension spring correctly. I can't see an image of your machine to know if it is top loading or front loading bobbin, sorry. But refer to your manual to ensure you get the thread fully into the tension device. With a front loading bobbin, there is a removable bobbin case. Ensure that this is holding the thread with enough tension, if you suspend the bobbin and bobbin case and just hold the thread tail there should be enough tension on the thread that the case just hangs, but if you give it a litle jolt, it should release some thread. Adjust the tension spring with a little screw on it in 1/4 turn increments until you get it to this point.
Try this link for some images and trouble shooting help on bobbin case. http://www.sewusa.com/Sewing_Machine_Repair/Thread_Tension_Settings.htm
If you can't get the tension right on the bobbin case at all, then take it to the Brother shop and buy a replacment one, sometimes the springs do fail on them.
Now put in a new needle and make sure you have used the right size needle for your fabric, ie medium weight woven you need a size 80 universal, but if it is a knit fabric like jersey you need a ballpoint 70 or "stretch 70" if its got a lot of lycra in it.
Now thread up the top thread and pay careful attention to getting the thread into all the thread eyes, particularly the take up lever and make sure it goes into the top tension discs fully (always thread with the pressure foot raised so the tension device is open). Lower the pressure foot and pull the thread just before the needle, it should feel very firm if the top tension is working right. If there is no resistance there, you've got a dodgy tension dial, take it for service/replacment.
Continue threading to the needle, bring bottom thread up to the top by turning the flywheel through one cycle towards you. Now hold both threads together at the back and test stitch a seam.
If you are still getting the noise from it and thread jamming up underside then the fault may be more timing related in which case you'll need to take it to a sewing machine technician too.