1992 Pontiac Bonneville Knocking noise on cold start around

92 Pontiac Bonneville SSEi SC 3.8 V6 ... on cold start I get a knocking noise from area under the heat sheild that covers the crossover pipe on the drivers side on the engine. I occurred that it might be a trans problem.....like cracked flex plate to converter or loose converter bolt or planetary self destruct. Or could it be a
heat expansion issue in the crossover jpint. Any suggestions in this area would be greatly appreciated. I spent over 30 years in automotive and some of the new stuff is still a learning experience for me. I guess that's the nature of the beast......thanks ...Ed