2000 4x4 4.0 - 86,000

So after I just got the truck running well again (due to bad plugs), I drove it for a couple of days and then I had a no start at the grocery store and had to have it towed home. Side note : after I replaced the plugs (autolite iridium), I could hear the spark through the radio. Yes the wires are all seated properly. Any thoughts?

The real issue though is the no start. It will crank and it does so very strong, but won't start. Yes, there is spark. No, there are no codes.

Here is what is new on the truck and what I have checked:
New plugs, wires, coil pack, crank sensor, fuel relay switch, IAC.
Cleaned the MAF, and checked the fuel shutoff thing wasn't tripped under the dash. Also, people say "turn on the ignition and see if you can hear the pump". Yes I know what it should sound like, but in the year I have had this truck I have NEVER heard the pump prime from in the cab or even when I had someone turn the key while I was under the truck (before any of this happened). So that's not a valid test.

So, could this be anything else before I go through the trouble of taking off the bed and replacing the pump? No, I don't have access to a fuel pressure gauge.

 

Well, to check for fuel other than the fuel pump SOUND, you could check for residual pressure at the fuel rail, or I suppose, pull the hose loose at the fuel filter and stick it in a bucket and see if you get some fuel out when you turn on the key. No fuel in the bucket... no fuel to the injectors. Good luck!

 

Replaced the pump and it started right up. While I had the bed off, I replaced the rear pinion seal since it had a slight leak. On the test drive after, I heard a slight high pitched noise from the rear of the truck the faster I went. I put a quart of gear oil in after I replaced the seal (which is about what leaked out during the process) is this noise the seal breaking in or should I add more oil or did I totally F something up.

 

I would check the actual gear oil level. It should be full to the bottom of the filler hole and no more. It could be over full... or low on oil. Did you tighten the yoke to specifications, or just as tight as you could get it? The yoke has a specific pre-load you have to put on the nut and most differentials have a crush collar that is only to be used once. I am more familiar with older 8" and 9" Ford diffs from the 1960s and 1970s. So other members please chime in here if this is no longer the case.

 

You are correct in your advice. If and when the yoke is removed, you are to replace the crush sleeve, they are not reusable. You can however get a crush sleeve eliminator kit that would allow reuse and only needs to be torques to spec.
I would say that the noise you are hearing is your pinion bearings screaming because you tightened them beyond their specified range.