No, it's the regular OHV 4.0 liter V6, which leaves the truck underpowered. I wish I could use my mechanical stethoscope to pinpoint the noise, but it's hard to poke around under the hood or under the truck at 20 mph. Whatever it is sounds like something small. That is to say, the sound is free of any low pitch components.
@myf16
No, it really isn't hard. I've successfully diagnosed both front and rear wheel bearings as being the noise source, as opposed to differential gear support bearing noise or pinion bearing noise, using this method.. Put the truck up on 4 jackstands very securly placed, wheels off the ground. Place in 4X4 HIGH, have a confederate (usually a wife), start the engine, place in D, and carefully run up to the desired road speed, while you crawl around underneath with your stethoscope, which can be a long screwdriver. I use Craftsman screwdrivers, since they have a nice rounded end on the plastic handle. Hold the tip of the blade against a surface where noise production is suspected, and at the same time depress your ear's little thingy closed with the round handle. You'll be surprised how many unusual sounds you will be able to single out, never before heard. I did this on the underside of rear differential, having a grumbling sound of bearing failure, heard the noise detected in the drivers seat, but found it much louder at the wheel bearing hub. Definite diagnosis! Here's the failed hub bearing outer race.
Some of my methods are not to be found in the literature. It is dangerous to crawl around under a vehicle with it's drivetrain in motion, yes. OTOH, only a moron would allow contact with rotating machinery under such conditions, won't you agree? I've messed with cars since my teens, 60 years. Formulated ways of my own, because of limited finances. I hope this helps you. imp
PS: A real doctor's stethoscope would be invaluable for this work.
