Project K1500: Posi-Lok or Bust

The Adventure

About a month ago we got a pretty serious snow storm and I decided I was going to have to drive Project K1500 to work.

On the way I took a detour through a field covered with about 10 inches of snow. Halfway through my four wheel drive started to jump in and out, and the light on my display kept flashing on and off. As I continued to work I came to a big hill that a couple of cars were struggling to ascend. I parked the truck at the bottom of the hill and walked up to give them a little extra push since they were in my way. Once they were clear, I got back into my truck and as soon as I pressed on the gas, my rear end went right off the pavement and into the ditch. Although it wasn’t too deep, it was more than the 2wd could handle.

I imagine the feeling could be compared to a mouse stuck on sticky paper, as I was unable to get out of this hole without my 4wd. [Editor's note - luckily Jarred always rolls with a digital camera, and is willing to share his follies with the rest of us!]

After driving around in the ditch for a few minutes, I decided I was going to have to winch out. To make a long story short, by the time I was out and back on the pavement I broke my taillight, spare tire gate, bent the side of the bed, bent the tail gate, broke the snorkel in two, ripped off my side grab handle, bent my mirror, and broke off my side marker light. [Editor's note - again, this is why we love Jarred. Only he would man-up and admit this kind of thing! Wish we'd been there to see it.]

I also broke the front synthetic winch line later that night trying to pull a semi off of a patch of ice. Since the 4wd wasn’t working, I wasn’t getting enough traction to pull steadily so I started pulling forward and tugging it. Unfortunately the synthetic winch line was rubbing too much on the edge of the fairlead and eventually broke. I will say that as far as I could tell the claims were accurate and the synthetic line did not snap when it broke and rather just fell to the ground.

I broke several components on the truck due to the 4WD going out. Click on pix to see detail in larger image.

Figuring Out What Went Wrong

Once the snow cleared out and the pavement dried, I was able to get out and take a look to see if there were any obvious problems that caused the 4wd to quit working. After determining that the problem was more complicated than just a loose wire on the transfer case, I began making some phone calls to the local parts shops. The only component they kept referring me to was some kind of a transfer case solenoid. I got online and checked to see if there were any other possibilities for the problem.

I used the Forums on Off-Road.com to explain my problem and almost immediately got a response back, which told me to check the Thermal Linear Actuator (TLA) located on the front differential/axle tube housing.

The existing 4wd engagement system uses a Thermal Linear Actuator (TLA).

The search for the new part revealed it was going to cost me about eighty bucks.

While looking online I came across a company called 4x4 Posi-Lok which has made an alternative front axle engagement system. This setup, referred to as the Posi-Lok, is 100% mechanical, which eliminates any possibility for a failed electronic engagement (which is what happened to me).

As I read through the additional information on their site I came across a section that explains the problems with the TLA. The first thing I read was that since the TLA relies on heat it can take longer to engage in cold weather, and upon submersion can cool too much and disengage. This definitely seemed like the cause for my failure, although instead of water I submerged it in snow.

Having read all of these details I decided to make a phone call to 4x4 Posi-Lok and see whether they could verify that the TLA was truly my problem. The representative I spoke with seemed very knowledgeable about my specific vehicle, and after I mentioned that my 4wd indicator light was flashing and eventually went out, he told me that the light is directly linked to the TLA. He also told me I can quickly and easily verify this by unscrewing the TLA from the axle tube, chocking the tires, putting the truck into neutral and 4wd. If the TLA were working, the piston should engage.

I ran outside and did what he told me and to my surprise, the piston did not engage. I was relieved to confirm the cause of my problem, thinking that it was going to be something more major and complicated to replace.

After compiling everything that broke from the failed TLA, I determined that I did not want to end up in this situation again. By the time I finally arrived at work, I was all dirty and full of mud from getting my truck out of the ditch. This all made the choice to go with the Posi-Lok engagement system an easy one.

Installation

The kit arrived quickly and I installed it the first chance I had. First step to installing the Posi-Lok was determining exactly where to put the switch. I had to route the cable and place the switch in a bit different location as the suspension and body lifts added another 9” or so from the axle tube. Even with that I still ended up with more than enough cable.

I drilled a hole through the floor right above the transmission/bell housing. Here I would have enough room below the cab above the transmission to route the cable to the passenger side of the engine, giving me the extra length to compensate for the 9 inch height difference.

I drilled the hole right in the center of the floor above the transmission/bell housing.	Now that the cable was routed to the axle tube housing I removed the TLA and threaded in the new Actuator Adaptor Housing and removed the bolt just to the right of the new adaptor.

I reinstalled the bolt with the supplied bracket and mounted the cable to the bracket.	Next I removed the axle tube housing mounting bolts and reinstalled them with the Bell Crank Support Bracket.

Now I installed the Bell Crank, Push Rod with Clevis, Dust Boot and all associated cotter pins. I also routed the cable through the Cable Clamp and aligned everything into the disengaged position.	I returned to the cab where I bolted the switch to the underside of the dashboard. Oh, and all the wires you see hanging are from another project I am currently working on at the same time.. rewiring..

I tested by engaging the Posi-Lok and taking a turn around the corner at the bottom of the street. The tires bound on the pavement, which indicated the the 4wd was engaged.

I am very happy with this installation and will be sure to update you after I get the truck out.