[2002ody]

My 02' ody has 250 miles on it with 80% city's miles. Yesterday, I tried to drive with D3 for about 5 miles and 50 mph was the fastest I go. This morning when I shifted the gear to reverse, there are a little clicking sound that I had never heard before and even on hot engine. I'm concerning is there a problem on the transmission or is it normal for Honda's transmission because this is my first Honda? any info would be appreciated, Thanks.