the sound usualy only occurs when it just shifts into OD and accelerating. the sound is compareable to a tin can with pebbles inside.
it sometimes happens in 3rd.
i already got under it to make sure there was no broken exhaust hangers, tapped the cat to see if the sound may be coming from there. that was solid.
im pretty sure i dont have spark knock. so maybe a loose torque converter, maybe a bearing in a the transfer case is destroyed.
what do you guys think.

 

I have the same sound, and I also had the same noise happen to an older minivan a while ago. turns out it was the exhaust rusting. my noise comes on when im about to take off, or when im slowing down.

on the minivan, it went on for about 3 years until exhaust just fell.

 

What your describing sounds like spark knock to me. how old are the 02 sensors ?. If there original with over a 100.000 miles on them, then they need to be replaced, they can cause the problem your having. when was the last time you did a complete tune up ?. Also, what grade of gas do you use ?. Around here were I live I have to use premium all the time because the lower grade gas has ethanol and it makes my truck run like crap.

 

i just did a complete tune up less than a month ago. i use 89 fuel.
the sound only happens when im on the throttle, usually when cruising at 40-50 mph in od. it doesnt do it all the time. not every time that i cruise at 40-50 mph does it make the sound. only sometimes. the sound is also coming from right under me.

 

Have you checked to see if everything under the truck is tight ?.

 

Yes sir. The sound is coming from under me

 

have you checked the output shaft snap ring on the t-case?

 

No, lemme Google it to find where it is an ill go check it.

 

Is it something I can check just by getting under it? With taking anything apart I mean.

 

No, gotta drop the rear driveshaft, and pull the tailhousing off the t-case. (block the front wheels first, leave the trans in neutral.) Doesn't take long to check it.