5 Spd tranny clicking sound in first gear?

I had my tranny rebuilt earlier this year and recently noticed a clicking sound under acceleration in first gear only. I put it in neutral and applied some gas to look for the same noise but did not get it. It only happens under acceleration in first gear. Is this normal to have a little but of noise or not? It is hard to hear over the engine noise, but if you look for it, it is there.

Rich