The vacuum actuator on the axle housing of your Jeep is responsible for locking the two-piece axle shaft together inside the axle when the Jeep is shifted into four-wheel drive. These actuators have been a source of irritation for Jeep owners. They are often removed completely, and the Jeep converted to a one-piece axle. If your actuator fails and you want to keep it, replacing it with a new assembly is the best approach. Trying to diagnose these units is difficult, and doing so is often more time-consuming than it's worth.
Raise the front of the Jeep with a jack and position a set of jack stands under the axle housing to support the Jeep while you work under it. Locate the vacuum actuator on the passenger's side of the axle housing; it has a skid plate over it and a vacuum line plugged into the end of it.
Remove the two bolts that retain the skid plate to the axle housing, using a socket and ratchet. Remove the skid plate and set it aside. Pull the vacuum line off the fitting on the end of the actuator and lay it out of the way.
Remove the four retaining bolts from the vacuum actuator with a 10-mm socket and ratchet. Lift the actuator off the axle housing. Scrape any gasket residue from the mounting surface around the hole in the axle with a putty knife.
Place a new gasket on the axle housing and position the new actuator over the hole. Slide the actuator into place, aligning the shift fork on the actuator with the collar on the axle inside the access hole.
Install the four retaining bolts and tighten them with a 10-millimeter socket and ratchet. Push the vacuum line onto the new actuator, making sure the fitting seats completely on the nipple protruding from the actuator assembly.
Position the actuator skid plate over the actuator. Install the two retaining bolts and tighten them with a socket and ratchet. Raise the front of the Jeep off the jack stands. Remove the stands from under the Jeep. Lower the Jeep to the ground and remove the jack.
