Do you have an IFS Chevy or a Jeep or Dodge with C.A.D. (Central Axle Disconnect)? Ever lost 4WD and you didn't know why...and the front driveshaft was spinning and nothing was broken...yet you still did not have 4WD?
There are a lot of Chevy, Dodge & Jeep 4x4s running around with some ill-conceived 4WD systems-trucks with 4WD actuators that engage the passenger axleshaft to the differential, utilized in an effort to minimize the front drivetrain's impact on fuel economy. These actuators can be found on early XJs & all YJs, Dodges from '85-'02, and the '88-'98 Chevy fullsizes & all S-Series Chevy midsize trucks. Chevy fullsize trucks use a thermal linear actuator that engages when it heated up (we're sure you can already figure out problems with this one), while Dodge & Jeep used a vacuum actuator that engaged when a vacuum boss in the transfer case allows a suction to come through the hoses
We curse all these systems! All the OEMs did was add more things to go wrong with your 4WD system.
Posi-Lok has been building solutions for the actuators for a long time now. Their replacement unit consists of a mechanical actuator that engages the axleshafts with a pull of a cable
 The Posi-Lok kit is not a...  The Posi-Lok kit is not a complicated kit to install. A pull-cable actuator comes with brackets to place it on the front differential. The cable pushes a pin that presses on a shift fork to engage a collar over the outer passenger axleshaft and the intermediate shaft. This goes for the Jeeps, the Dodges, and the Chevys. |  For our fullsize Chevy kit,...  For our fullsize Chevy kit, the front pivoting bracket (and bellcrank) ties into the two bolts that hold the front differential passenger tube onto the frame. These are not studs, so you'll have to have a box wrench on the back of these to get them off, and man those bolts are on there tight from the factory! They should be, as they hold up the differential. |  Here is the stock thermal...  Here is the stock thermal linear actuator (from a Chevy) above the new Posi-Lok push rod, dust boot, and adapter housing. You simply unplug the thermal linear actuator, tuck the other side of the harness away in the wire loom, and unscrew it from the differential using a big box wrench or adjustable wrench. The Posi-Lok assembly goes fits directly in its place. Add some grease onto the push rod and some RTV sealant to the housing threads, and you should be good to go. |
 The Posi-Lok cable has a bright...  The Posi-Lok cable has a bright red handle that attaches to a (supplied) bracket below your dash. You'll have to drill a hole (or find an existing one) in your firewall. The cable feeds down to a cable bracket on the differential. The cable itself attaches to the end of the bellcrank and with a push or pull engages or disengages the push rod from upon the shift fork. |  Your finished product should...  Your finished product should look like this for any K-series '88-'98 Chevy. The same idea is incorporated into all of Posi-Lok's kits. If you're still scratching your head after seeing this image, you might want to think about getting a more knowledgeable friend to help you complete the project. | |