A 2014 Ford F-150 came in with the 4wd not working. I found that the vacuum-operated wheel hub/axle shaft coupler (Ford calls it an IWE, for Integrated Wheel End) on the left front wheel was bad, not allowing the axle shaft to turn the wheel. These are so bad, in fact, that the aftermarket doesn't even offer a replacement. Instead, there is a kit that replaces both sides and essentially locks the hub/axle together and doesn't allow it to freewheel. And if you're asking why we didn't get a direct replacement from the dealer and do just the bad one, A, they didn't have it (par for the course here); B, one IWE costs more than this kit; and C, the other one is likely to take a shit later anyway. Anyway, the call went smoothly, no hassle, and Car Shield will pay $210 of the $394 bill. Not what they imply in their advertising, but at least they paid something instead of trying to weasel out of it.

This IWE setup is either very clever or very stupid, depending on your point of view. It uses engine vacuum to engage or disengage. Oddly and (to me) counter-intuitively, the vacuum holds the IWEs disengaged when in 2wd and vacuum is taken away to engage them in 4wd. Also, the new setup, instead of letting the hubs freewheel, now turns the axle shafts and front propeller shaft all the time. Other 4wd setups do this, too, so it shouldn't hurt anything.

I recall, and so did Chevrolet, a '95 Blazer I bought new had vacuum operated 4 wheel drive. Simply a dash mounted push button. IIRC, you needed to reduce road speed or stop to engage it. It didnt work right from the start so the recall was spot on.

Yes, on the S-10 pickups and Blazers, the front diff had its axle shafts coupled by a vacuum servo pulling a cable. And it was cleverly located under the battery so acid could drip on it. SMH.

I like the old style, manual locking hubs.

Bad weather, lock them in and if the road suddenly goes to shit, you pull the lever to engage the transfer case.
Very nice driving down the road and being able to engage the four wheel drive at highway speeds.

But we won't talk about the 700r4 which was in said vehicle.

Google reviews of CarShield.