Metallic Slap After Starting

2.7 5 speed manual

Anyone else get a single metallic slap right after the engine catches? I hear it maybe 50% of starts. It sounds almost like the tailpipe gets torqued and hits something. Sounds from the rear of the truck. It seems possible given that the engine and trans mounts in this truck are made of jello but if that was the case I'd think the forces on the mounts during actual driving would be much greater and I'd hear this sound in motion too - but I never do. Just wondering if anyone else has experienced/pinpointed what this might be. It seems fairly harmless.

I do notice that the brake drums sometimes clunk the first time I apply the brakes (after the parking brake has been set and released). But that seems unrelated.

 

I think you're hearing the exhaust pop. Normal on the 2.7 trucks, gets worse in cold weather.

Think of it like a small backfire.