Hi,
your details are a bit vague but I would recommend getting a mechanic to look at that right now. Just knocking can be fairly minor, but grinding could be something a bit naughty like bearings or brakes. I think the 1st, 2nd gear thing might be a red herring, if not it could be the gearbox. Either way you should err on the side of safety.
Cheers
Ken Chapman
April 2007
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