Well...here's my next question for everyone:
It is looking and sounding like the pinion bearing in the rear end of my 2006 Expedition is out or headed that way.
Pretty loud howling from 40 mph to 80 mph.
Replaced the wheel bearing hub assemblies since each of those was pretty suspect over the last 6-8 months.
Truck has about 160k miles on it now.
Every time I replaced a hub, things got better and quieter, but I could hear the next worst bearing.
Now it is looking like the rear end itself is making noises.
Once weather cooperates I am going to start hitting it with my laser thermometer and see if that shows anything.
I see a little bit of play at the other end of the driveshaft, at the transfer case.
Maybe a few thousandths, .005" or so when I work hard to push the drive shaft side to side at the transfer case end.
Thought I might have been hearing the tail shaft bearing a few weeks back.
I checked all the lube and fluid levels then, all looked good.
The following week (when I repaired a broken wire to my EVAP system-another of my threads getting help here ) I see gear lube leaking at the pinion seal.
Going out this afternoon to see if anything else points to the diff.
IF...it does I am wondering...
is it possible to do anything on the front of the diff at all?
Can the pinion bearing be worked on from the front at all, or does the carrier and everything have to come out the back to get at it??
Not sure if it is something I am going to tackle as the truck has more issues and may be getting replaced soon but if it is a matter of dropping that shaft, removing pinion nut, pulling seal, and being able to remove and replace the bearing, just may try to do it in the driveway and garage...
Doubtful...but have to ask.
THANKS all around once again ! ! !

 

You sure it's an 8.8 and not a 9.75? I could be wrong but I thought the 8.8 was for the front and the 9.75 was for the rear?

 

That very well could be.
Sorry
Stock axle in it.
3.08 gears open diff
No fun towing for sure

 

Yes you have to disassemble the carrier to change the pinion bearing(s).

 

I thought that was the "case"...
Kind of makes me miss all the old 9"s that were in my old trucks and Broncos.
Still not 100% sure where the howl/whine/noise is being generated.
Pinion seal leak just became noticeable within last 3 weeks to a month ago.
Very small leak, nothing on garage floor; just seeping onto bottom of diff.
Had the rear end raised up and tried to see if anything seemed loose.
Did not find anything at pinion.
Seemed like there was more play in the diff or gear set itself than what I would have expected.
It is an open diff so I held the driveshaft in place and turned one tire until it started to try and turn the driveshaft.
Opposite tire would move other direction, but seemed like it took a lot of travel before things connected.
Maybe a 1/16 of a revolution of the tire.
Felt like there maybe excessive lash or clearance between ring and pinion...maybe??
The front of the rear shaft where it enters the transfer case tail shaft housing does seem to be getting more slop/play in it too.
Wishing I had a hoist that I could trust to run the truck and let tires spin while in the air.
May visit a friend who has a shop and see if that is something we can do...?
With some other issues on the vehicle, may sadly be time to replace it entirely too
Thanks as always for the info and helpful advice

 

What's the condition of the u-joints? Some of that play can be the driveshaft turning and the tranny/t-case plus the u-joints taking up slack.

 

I don't see any play in the driveshaft u-joints or cv joints in the rear axles.
I am guessing by sounds and way it seems that it either needs pinion bearing or tail shaft bearing in the transfer case.
Sounds a lot like it did when wheel hubs/bearings get bad, but turning doesn't effect it at all.
Changes pitch with wheel speed, doesn't react to whether or not giving throttle or coasting. Just vehicle speed-road speed.
Thought putting it in 4wd and getting front end to pull might take stress off and quiet it down, but doesn't change either.
Tried hitting pinion area of diff and the rear of the transfer case with my laser thermometer yesterday but didn't find any high temp areas.

???

 

It will only run hotter if the bearing isn't getting lubricated.

 

You got a point there.
It is full and I was surprised how fresh the lube in the rear end looked when I checked it.
Transfer case also.
Thanks for that too.

 

Well, another week of listening to it howl...
The pinion seal is still dripping slightly.
But the driveshaft's front end at the transfer case seems to have more slop/play in it.
I can even see rubber dust from seal wear around the area where the yoke enters.
I am planing to compare with our 2004 Expedition tomorrow and see if there is drastic difference.
Been searching to see what it takes to replace the tail shaft bearing and seal if that is in fact the issue without much luck.
Any info on that available?
I only see one nut when I looked quick at what it might take to get at it...
Splitting the case?
Able to use a puller from the rear where the shaft goes??
Appreciate it if anyone has info as to what it takes ! ! !
As always THANKS