Flappy noise coming from transfer case/transmission area.

[BiLLz0r Advanced Member Find all posts View Profile Close BiLLz0r]

We have this noise coming from the transfer case area when accelerating. If the car is coasting or breaking it doesn't do it. The noise is a type of flapping/dull clicking noise. Any ideas what it might be?
I thought it might be the bits of plastic bolted to the underbody guards so took them off. I also noticed the afm sensor clip had broken off holding it to the bracket so cable tied it back on. Took it for a test drive but it's still there. After about 20mins or so of driving it seems to get quieter. It's very noticeable when cold and very annoying. Inside the cabin it sounds like it's coming from the area under the center switch blanks/low range stick.

[BiLLz0r Advanced Member Find all posts View Profile Close BiLLz0r]

No one has any ideas?
Oil levels seem fine. I tried to listen for it whilst the car was in park and although I can just hear it it's way too noisy to tell where it's coming from.
It's due for a 200k service soon so might just get the mechanic to have a look.

[BiLLz0r Advanced Member Find all posts View Profile Close BiLLz0r]

Well I've been driving the Prado the last 2 days. Yesterday the noise got to me too much so dropped it into the Exhaust place that did my cat. He found a leak in the gasket between the extractors and cat on the passenger side. Today he fixed it and it sounds like a song now. It just puuurrrrs.