Banging noise Heard after start up

[jtnm]

I have a co-worker with a 07' 6. 7 auto, he says when the truck sits for a day or so, he firsts starts the truck and around 2 to 5 seconds later he hears a loud bang from under the truck, possibly from transmission or torque convertor maybe? Sounds like something metal. Has any one else heard or had this type of noise. P. S. the air condititoner is off (dealer said a/c was on) "not the case".



thanks

jtnm

 

[jelag]

If the truck is in the defrost mode, or you ask for air to the windshield the AC will start on its own..... Is the heat/ac unit in the off position?

 

[jtnm]

If the truck is in the defrost mode, or you ask for air to the windshield the AC will start on its own..... Is the heat/ac unit in the off position?

Nothing is on, yes it is in the off position. The noise is heard when the truck has been parked overnight or a few days. Its only happens when the truck has been off for long period of time. He says sounds like a cling sound.

 

[Jeb_H]

Dude, you might want to see if the tail pipe behind the rear axle is hitting the leaf spring by it. Mine was and did the same sort of sound. It gets real close to the spring.



You can loosen the last section clamp and twist the tail pipe downward just a little and mine moved away from the spring far enough to stop the banging of the spring right at start up when the motor torques over... Might be worth a look see anyway

 

[Jeepstang]

Not sure if this was his case or not but I had this experience the other day

I never paid attention before and I think this was the first time that I noticed it. When I started the truck the voltage gauge read almost out of the range on the lower end of the scale on the gauge. after running for 5-10 seconds or so the voltage regulator must have turned the alternator on full field for a second and the entire truck shook and made a banging sound and I watched the gauge go back up to the higher end of the normal range around 14 volts or so. i would have him watch the voltage gauge and see if he has a similar experience.