Rattle when my truck starts

so when my 91 gmc starts it has a little rattle, but only when it starts and it last for about 4 or 5 seconds, just wondering if anyone would know what causes this? thanks for any info

more then likely it is a lower end main bearing knock until oil press goes up.

gm was aware of this problem on these trucks and released redesigned rear main bearings.

as long as oil pressure is good i wouldnt worry about it. just take it easy on the eng until oil press is at normal level. hell i have a 97 with 194k on it and its been making the same noise since 100k.

alrite, so how would i go about repairing this?

Also check torque converter bolts. Loose torque converter bolts and a cracked flywheel caused that condition on my 90.

ok, i'll check it out, i was thinking possibly a flywheel problem, but i was just tryin to see what other problems it could be, thanks