Drivetrain failure
 

Greetings -- My daily driver is a 2000 Expedition XLT 4x4 4.6L with a new drivetrain problem.

Driving home this evening, I came to a stop before turning left into my subdivision across traffic. While accelerating, my truck when "bang", like it had been barely hit in the right-rear bumper, then went "thump-thump-thump", as if something were stuck in the wheel well. The thumping continued I brought it to a stop and put it in Park with the parking brake pressed.

Upon inspection, I found that the truck had not been hit. So, I put it back into gear to head home. As soon as the truck started moving, more bangs and thumps. I put it in Park and it rolled forward---man, did I hit the parking brake, quick! I tried reverse, and after a foot of movement, more bangs and thumps, and now some crunches that sound like chunky metal in a slowly-rotating garbage disposal.

I put it in neutral, then switched it into 4x4, then 4-Low. No unexpected noises. I returned to AWD, and put it in Drive. The truck pulsated, about once a second, feeling like it was trying to get into gear. I rowed to Reverse, same thing. I was able to row through the forward gears and feather the throttle to get the truck down the street to my driveway. More bangs and thumps, but few crunches.

After parking the truck, a physical inspection shows nothing unusual to my eyes. Driveshafts are nice and tight, no (new) leaks or holes, etc.

Could it be a dead transfer case? A dead transmission?

Upon inspection at a transmission shop, it was immediately obvious that the differential exploded. They haven't broken it down enough to see if the axle shafts are damaged. Quote including 5.5 hours labor is $1800-2200.

I'm capable of doing the work myself, so I'm going to go on a parts hunt before I commit to having the shop do the work. However if parts cost me $1200, and their labor is $600, I may just have them do the work. In my home and work situation, there's a lot to be said for moving past the problem as quickly as possible.

Thanks all for the help thus far :) :)

Any gotchas to watch out for?

Checked it out for myself -- the carrier went, "crunch." Parts everywhere inside the housing. Ring gear is chewed up, too.

I found out the owner of the transmission shop is a fellow musician, he and I swapped a few stories of the local music scene and he cut back the labor charges and the parts markup. Highest he'll charge is $1,300, +$125 if I need an axle due to spline damage.

Not a bad deal considering the weather is in the mid-30s, and my at-home shop is an exposed carport :)