Drive shaft fell off my navigator

My boyfriend went over a huge puddle and as soon as he did, he heard a loud grinding noise from under the car. It drove for about 20 seconds and then stopped moving completely. Tow truck driver looked at it and said he thought it was the drive shaft. Would that coming off keep the car from moving at all ? How easy of a fix is this?

Yup, it definitely would.
It hangs below the vehicle and is fairly easy to remove and replace… but you’re lookin’ at about $400 for the driveshaft (if it was damaged) combined with the cost of the U-joint plus labor. And if upon testing it’s determined that you have some other condition causing oscillations that led to the U-joint failure, well… who knows.

Since you haven’t provided any details, I’ve assumed it’s an aging, high-mileage 2WD?

Its a 4wd. Don’t know much else about it. But the shaft seems to be fine. I think it may have been the bolts or the u joint. Not sure if that makes any sense

Driveshafts come out because a u-joint has failed, usually due to wear or in the old days, lack of grease. Are u-joints grease-able these days? It has been a long time since I had anything rear drive. The puddle probably had nothing to do with it.
The fix could be as cheap as getting a whole used driveshaft from a junkyard. The front of it slips inside the tailshaft of the transmission and bolts to the differential.
You need someone knowledgeable to look under the car first to see if that is what has happened.

Unless there was a pothole living under the puddle. That’s where potholes go to hide.

The fact that it’s a 4WD definitely changes the potential cost picture, but until it’s properly diagnosed it’s tough to guess.

“The fact that it’s a 4WD definitely changes the potential cost picture”

I’m not sure about that.
While there are both 2wd and 4wd versions of these vehicles, since these are essentially RWD vehicles adapted for AWD, is the driveshaft running to the rear axle different on the two versions?

“Don’t know much else about it. But the shaft seems to be fine. I think it may have been the bolts or the u joint.” - OP

Depends on what’s wrong. However, to answer the question, the 4WD doesn’t use the same driveshaft. It has a Xfer case in between the tranny and the rear differential with two driveshafts, one driving the front diff and the other the rear diff. If the Xfer case is broken the cost rises.

The problem is we don’t know what’s busted yet, and the 4WD adds some more possibilities.

Thats what is broken. Everything else is fine.

The first picture shows that the bearing caps for the u-joint are missing. But all will come with the new u-joint.
The second picture shows that when the u-joint went it tore the ears off the Differential Yoke.
You should be able to order a new Yoke along with the U-Joint.

Yosemite

I should have added.

You can remove those 4 bolts that face up in the 2nd picture but use a 12 point wrench.
The new yoke can be re-installed on the new U-Joint along with the drive shaft and it pretty simple to re-install the drive shaft.

Take the old yoke with you. I may have my terminology off and it may not be called a yoke.
They will know right away what it is when you tell them it’s part of the drive shaft. They can also give you the torque numbers for when you tighten those four bolts back down.

Yosemite

You might want to spray those bolts with penetrant repeatedly over a few days. Then use a 12 point box end wrench and a hammer to break them loose.