Explain rear Differential and pinion to a dummy. 2005 XLS

[louhazosc]

Hello,
2005 Expedition XLS. Had a once over done on it and all suspension and gaskets were bad.
I did the upper control arms, shocks, ball joints, tie rods, sway bar links & bushings and next is the ever so annoying oil pan gasket.
So that's my level of knowledge. Alternators, starters, etc.

Was also told the differential isn't even worth a rebuild and needs to be replaced and there is an awful noise coming from the pinion.

I know ZERO about how to do this and more so and where I'm asking for help...what should I even be looking at for parts?
If I look on Auto Zone (no, I won't be buying one there) I see new Zumbrota 3.73 ratios around $1800.
Looking on ebay I'm seeing 3.73 ratio differential "Carrier"...I know this makes me give up a man card but what does it mean when it says carrier?
Still, only a couple hundred.
So then would I need the gears and seals kit.

Basically what would be your opinion on going about this for a complete novice. I am NOT doing this myself. Don't worry.
Would it be the simplest and longest running solution to just drop a couple grand and drop a whole new diff in?

Then there is the Pinion issue...Pinion seal? Again, not a job I could do. I know my limits and no lift. It'd be on the ground in the driveway. No thanks. Suspension rebuild was bad enough on the ground.

Thank you much.
Any links or anything to help me gain knowledge and understanding it better. Anything is appreciated.

 

[SafariGoneWrong]

The differential carrier is what you see under the vehicle with the axle shafts and driveshaft attached, most folks simply call it the "differential". The differential itself is inside the carrier and it is what the ring gear bolts to, it contains the spider gears and side gears. Not a bad idea to be looking for a working as removed differential carrier (with all the internal components of course) if you think you can remove it from the vehicle. Bad differential noises are usually due to worn pinion bearings and/or carrier bearings. Pinion seal problems show sweating or leaking around the pinion flange area but won't cause noises. Full disclosure--I've never removed or set up an Expedition 9.75", my experience is plenty on Ford's 8.8" but they are functionally similar. If going with a junkyard differential, I wouldn't preemptively replace the pinion seal because you have to be careful getting the pinion bearing preload right after removing/installing the pinion flange. Not getting it right can set up for problems down the road (no pun intended).

 

[whtbronco]

Zumbrota is one of the few companies rebuilding the IRS 9.75 diff. It's the one I decided I would go with had I bought a reman diff. The parts can be purchased separately to rebuild yours with a better limited slip diff like the Eaton TruTrac and a local 4x4 shop can do the work for 4-5hrs of labor. I was quoted $600 labor by a local shop.

I will also add that many salvage yards offer a warranty. My local yard is 60 days. All they will do is replace it, they do not pay labor or anything else, but it just might be worth it. If you could find a diff with 100k miles or less it might be worth it.

 

[whtbronco]

I believe the carrier is what the pinion gear mounts to, that's what I've always known as the carrier.

Here's a limited slip example(purple springs) and an open example:



A Zumbrota diff will likely last the life of the vehicle. Truth is there is reason not get a Zumbrota diff from AutoZone, they are just reselling the same product you'd get from Randy's Worldwide who now owns Zumbrota. AutoZone can make it easier at times too since they are local you have a place to drop off the original diff.

 

[louhazosc]

Thanks for the reply guys. I wasn't too far off.
Why I said I wouldn't buy from Auto Zone was simply thinking "big box" store, a la Home Depot. As stated, Randy's kind of backs that up.

All and all...I personally am more comfortable changing out an entire differential/carrier versus gears and seals. I was also told there is zero chance to rebuild mine.
Also as I said, I'm not doing this as no lift. Removing and replacing a differential is not a jack stand driveway job. OK, it can be, but why put yourself through that.

This gives me a way way better idea of what prices I'm looking at and that was the big question. I was told around $4k but it's far less even if I go new diff and the pinon seal.

Thanks again. Helped a lot