noise after warming up

Hello all. I will do my best to describe my issue. Went on a roadtrip 2 weeks ago. After about 30-40 minutes I started to hear this what I can best describe as " a rock being thrown on my floorboard/tightly strung guitar being plucked" That is what it sounds like in the cab. Sounds like it's coming from the middle left to  rear left. I hung my head out the window and it is more like a loud clank. It is also very inconsistent. It could go 5-10 minutes without hearing it but then I could hear it back to back or five times within a minute. Like popcorn. The truck continues to run normally just for the fact that this noise gives me extreme anxiety.
I normally drive just 20 minutes to work so the truck never really gets to heated. This problem may have existed for awhile. But after this roadtrip and now longer trips of over 30 minutes I notice it. (Recent resolved issues include, rebuilt transmission, front brake pads, front wheel bearings) Two mechanic shops expected and  said my U joints are fine. Any ideas where to start? It's really hard to diagnose since the truck has to be running hot to hear it and even so it is very inconsistent. Thanks for any advice.  (03 Cladded Z71)

I suspect it's coming from the transfer case.

enoniam said:

I suspect it's coming from the transfer case.

Click to expand...

Ah, the dreaded pump rub good call.. Check the back of the transfer case for a small hole and the oil level..

May not have any oil in it.. If you can use a mirror and look around the case and see if there is fluid on it that might be a good place to start as already said.

Do a search on "Chevy pickup Transfer Case Pump rub through" and you will find many threads on this topic.

DO NOT DRIVE THIS TRUCK...

Verify if this is the issue or not. If it is the issue you can expect a sudden boom as the transfer case internals come apart due to lack of lubrication. It only comes out while the truck is running down the road so you seldom see a puddle. Note that if the transfer case grenades the repair becomes a lot more expensive than just installing a case saver and a new half shell. You could have chain wear at this point if has been going on for a while too.

Good luck!

Rodney

Ok. Well I do not want anything to explode. A little freaked out now.   It is dark outside but I shined a flashlight as much as I could up and around the case and I do not see any fluid. Looks dry. We live on an incline so as soon as I get it to level ground I will check the fluid level or take this thing in to the shop ASAP.

Take a look at the heat shields on the catalytic converter also.

My 04 z-71 avy has the catalytic converters rattle as well. But mine sounds like coming from passenger side middle.