I can't really tell what's going on. at first I had a squealing chirp sound that I suspected was my belt that I only noticed when I would drive on my street because I was going slow enough to hear it. I later found out that there are axle u joints on 4x4s too so I checked those with the truck on the ground and both those are shot. I didn't have to rotate the axle and jack it up or nothing. you could wobble them by hand with it on the ground.

ok. what worried me though was it sounded different today. I noticed a fan like sound going woooooop woop like whirring almost but not metal on metal. me being the paranoid guy I am I tried to see if I could find any play in the rear driveshaft to see if my piņon bearing is lose. no play. I don't have a good jack, just a cheap one that barely reaches my truck with blocks on top just incase of a flat. it came in one of those cheap roadside kits and there's no way id trust it to jack the whole rear end up.

my question is when a piņon goes bad is the only way to check it for sure is to jack it up and give it gas ? or will it always have play ? sorry if that's a really stupid question but I've never heard a u joint make that kind of sound before. at least not online. then again I get real paranoid about any noises from my truck because the first one I had made a very subtle gear whine that I thought was power steering or something and sure enough my tranny blew within 2k miles of ownership. at least it broke down on me right down the street from my house.

 

May not hurt to have a look at your brakes as well. They can make some odd and strange noises when they get worn down.

I would suggest picking up a jack, and some jackstands, and doing a thorough inspection of the running gear. See what ya find.

 

You can use a jack with a fairly short reach if you put it on the shock perches on the rear axle. If you're working in the dirt you can modify some jack stands like I did and weld a piece of plate steel (I used 14 gauge) to the base and they won't do a leaning tower of Pisa impersonation every time you put weight on them.

You say fan noise but not metal rubbing metal, the chain in the transfer case might make a noise like that. Check the fluid.
The gears in the rear end could also make that noise.
The springs in the rear brakes could also make that noise, I had one pop off once and half of the springs in there got ground down to dust, the spring kit at the parts store is pretty cheap.

Here's what a chipped pinion gear that hasn't gone bang yet sounds like

 

I had a similar problem on my 3rd gen. Would squeek at low speeds and chatter from time to time. But not when going over 30mph. Lasted for about a month then my center bearing went completely out. I believe it was caused by a universal joint going bad.

 

so now my truck grinds and shutters when I come to a complete stop so I'm about 99% sure its a u joint or my brakes. I just tried to go to work and it started today so im gonna jack the truck up and see what I find. I don't know if front u joints can cause it to shutter or grind like that when slowing down but the noise sounded like it was coming from the rear. its only when I slow down so its not the rear end. I had to replace wheels studs just 3 months ago and the brake I looked at looked good. at least that's what my buddy said. Ive never done brakes before.

ive kept an eye on that seepage from the rear end and I wiped it down. its just a really slow dry seep so idk if its worth replacing the seal yet.

the wooh wooh sound is probably my u joints I bet and the squealing / squeak sound when slowing down was probably my wear indicators.

my boss still wanted Me to drive to work. I said **** no.

 

I would caution driving it with the shuttering as well. I ignored mine the day it started to shake and shutter. Ended up snapping the yoke at the trans overdrive. That is a very specific part on a dodge truck as it took me weeks to find a shop that could order it and cost a good bit ($190) for my negligence. Not to mention paying a shop to tow the truck and install the part with new u-joints. But what you are describing sounds just like what happened to me. If your truck is an extended cab and long bed look at the center bearing on the drive shaft. Its so close to the center of the truck that the squeak can sound like its coming from anywhere.

 

I don't see a center bearing anywhere on my driveshaft. is this just a 2wd thing ?

 

Nope, it's a wheelbase thing. My 4x4 club cab long bed has one. Not sure which ones have it and which don't. I'm guessing regular cab short bed does not have center bearing.

 

Take close look to the front axle shaft joints. I had slight ticking sound from them, and since I didn't fix them in time, I ended up taking front axle apart on a road trip because RH joint busted and it was just a moments away from destroying the u-joint ears at the axle shafts.
And while you are there, check the dust shields. If they are rotted and leaning against the rotor, they'll make noise.

 

When mine was making really rude noises when I stopped, it was the rear brakes being worn down to the rivets. You would have thought the whole truck was going to shake apart. New shoes/hardware/cylinders/lines, and all was good. (one of those jobs where taking one thing apart, breaks the next, and so on..... )