1995 Tahoe Clicking noise

[1995BigRed]

Hey folks, my name is Vince and I just bought a 1995 2 door Tahoe LS 4x4. It has 119000 miles and is a two owner lady driven truck. When I bought it I did not hear a clicking noise coming from what seems to be the area around the 4x4 shifter on the floorboard. This seems to have started this morning on my way to school. I checked all my fluids, tranny, oil, power steering everything is full, no oil or transmission leaks. This click happens only when the truck is cranked up. It is rythmic and when in park or neutral, I rev the engine, the clicking frequency gets higher. It also follows the same role while driving down the road. At highway speeds (65+) it becomes a lot less noticeable. Transmission shifts great both at low rpm and WOT. Any clues or help that anyone can give me? Possibly transfer case fluid? Maybe just a heat shield. If u get under the truck you cannot here any noise at all.
Any help is greatly appreciated!

Vince

[glenncof]

Just a wild guess.... Could be a lock-out relay clicking...

[AACrT]

You may be hearing a noise eminating from the catalytic converter, when they begin to load up they will get very hot, then you may hear a click from that, or if the internal material has broken apart, you may be hearing it "rattling" around at higher RPM's. Lightly tap on the cat to see if there is anything rattling around inside, then run the engine under the same circumstances till you hear the clicks and check cat to see if it is glowing.