Hello I have a 1999 Ford Ranger 4x4 it has the vacuum setup. I'm wondering if I can change it to electric.

 

Welcome to the forum

Yes, 1998-2000 Rangers 4x4's use PVH(pulse vacuum hubs) on the front axle
But transfer case was still electric shift

There were no electric hubs, just automatic, PVH or manual

The 1998-2000 front axle PVH hubs can be changed to Manual Hubs, only brand that fits is AVM Rugged Ridge

How-to here: 1998-2000 Ford Ranger Manual Locking Hubs : The Ranger Station

When you have manual hubs you can leave them Locked throughout the Winter months and just shift transfer case to and from 2WD or 4WD high without getting out of the truck, and you can still do it "on the fly"(while moving), just like with Auto or PVH hubs.

It doesn't hurt the front axles to be Locked when driving on dry solid ground in 2WD, in fact 2001 and up Rangers had "Live Axles" always locked front axles, so exactly the same as leaving manual hubs locked.

Benefit of unlocking the front hubs is MPG, you gain .3-.4 MPG with unlocked front axles, yes ain't much but ain't 0 either, lol