4x4 Posi-Lok

[arveetek]

After nearly 20 years and many thousands of miles of trouble-free service, the thermal actuator quit on the front axle of my Tahoe. This is the electrical device that disconnects the passenger side axle shaft from the differential. This prevents the front driveshaft from turning when in 2WD, saving wear and tear and improving MPG.

I was on a 4x4 trip in October, and at the end of one of the trail rides, I noticed the 4x4 light on the floor shifter was no longer illuminated. This light normally turns on when the front axle is engaged. I did some trouble shooting, and verified that the front actuator was no longer working, so no more 4WD!

The most common solution is to upgrade to the newer electric actuator instead of replacing the original thermal actuator. The electric version is faster and more reliable, but it does require some wiring modifications, including running a new wire from a 12V + ignition source. I seriously considered this option, but I decided to go another route, and install the fully-mechanical 4x4 Posi-Lok:

https://4x4posi-lok.com/product/psl600-4x4-posi-lok/

This replaces the electric/thermal actuator with a mechanical version that is operated by a push/pull cable mounted in the cab. For me, there were two advantages with this option - 1. No more having to rely on anything electrical or electronic; even with the more reliable electric actuator installed, it would still require an electrical signal from the floor-mounted shifter to tell the actuator to engage. 2. The Posi-Lok will stay engaged, even with the ignition turned off; this is an upgrade in safety when using 4WD and parked on an incline; with the electric/thermal actuator, the front axle could disengage when the engine is turned off, causing a loss of traction when parked off-road, when winching, etc.

The install was actually easier than expected, and even moving slowly due to a recent minor surgery, I was able to complete the project start to finish in about 2 hours. It works great, and is simple to use.



New actuator installed:

https://live.staticflickr.com/65535/54136888377_e07b712dab_b.jpg



Push/pull cable mounted beneath dash:

https://live.staticflickr.com/65535/54137740851_6ca408bde6_b.jpg



2WD position:

https://live.staticflickr.com/65535/54136888367_7e83f1262d_b.jpg



4WD position:

https://live.staticflickr.com/65535/54138024428_b928b2d088_b.jpg



4WD indicator still works on floor shifter:

https://live.staticflickr.com/65535/54136888357_f456a6d1e3_c.jpg



Back on the trail again:

https://live.staticflickr.com/65535/54086988527_7e5c5c84e6_h.jpg


I am really pleased with the product, and feel like I have a very reliable 4x4 that will work every single time I need it.

As a side note, if you ever find yourself in an emergency situation and your actuator won't engage, just grab a 3/4" impact socket. Remove the original actuator, toss the 3/4" socket into the axle, and then reinstall the actuator. This will cause the actuator to push on the lever inside the axle and engage the front axle permanently, and makes it just like a Jeep Wrangler - as soon as you pull the transfer case into 4WD, you're ready to go! The front driveshaft will spin at all times, though. I actually did this for a few weeks while I contemplated what I wanted to do. However, I could tell my front driveshaft was not perfectly balanced, and I could feel it vibrating, especially at interstate speeds. You can actually buy a "PermaLok" that does this exact thing, but there's no need to spend over a $100 when a perfectly good socket does the job! :D I decided I wanted to be able to have a front axle disconnect after all.

Casey

[Yukon6.2]

Thanks for the write up and information
I will be looking at getting one for my Diesel Sub, as it will be our road trip vehicle with off road intentions.

[arveetek]

Thanks for the write up and information
I will be looking at getting one for my Diesel Sub, as it will be our road trip vehicle with off road intentions.

If you purchase one, I suggest watching a YouTube video on how to install. The included instructions are confusing, and they even recommend draining the front diff fluid, which is not required at all.

Casey

[Robyn]

Great posting

Those thermal actuators can be a real pain.....And they never fail when you don't need the 4x4 :rolleyes:
I have replaced a few over the years.....
I think you made the best choice with the posi-lock.....

[JohnC]

I miss my Warn hubs, and slogging through the muck to lock them. (Actually, as you all know, the key is to lock them before you go into the mud...)

[Robyn]

Locking hubs are IMHO the best thing ever invented.....
The new single wide bearing "Hub assembly" are a poor design and do not do well with big tires....
The electric actuators (Or vacuum or ?????) are trouble waiting to happen and at the worst possible time.

Flip the hubs in before you get into the rough stuff and then yank the lever when needed.

In all my years with 4x4 rigs....Never had one of those fail

Some of the "Auto lock" hubs were sketchy.....Take them off and throw them in the dirt....Get a nice set of Warn hubs....Life is good....
I will say this....Most of the stock GM standard locking hubs were decent.

Trying to improve on near perfection is usually a waste of time (Auto lockers)

Now we have a button on the dash that tells the computer what to go do and then various modules and the maze of wires to make another gizmo activate the parts to get the 4x4 working.....
What part of insanity is this ???

With the 4x4 shifter off the floor it allowed the center console to cover the hump area.....aesthetics was more important the common sense.
Tossing your gloves on the hump to dry by the heater vent was perfect......

I digress....

[Yukon6.2]

I agree to much BS in modern vehicals
Locking hubs and a leaver, pretty much bullet proof compared to a new truck where a bad wire will leave you with a useless truck in 2WD
my 04 GMC gasser has an issue with the electric passenger side window again, i fixed it about 10 years ago. I have never had a manual window give me grief since i started driving. It's always the electric ones that FU ,switch, wire, motor. Have had issues with all of them.Up here in the cold it is usually the wire that breaks by the door hinge.
The last time it was the motor in the 04,water gets into the housing rusting the motor shaft which makes it hard to turn which then pops the circuit breaker leaving the window down.

[Robyn]

The stuff of late use "Body control modules" to run all the accessories on the rig
The window button just tells the BCM what you want and it activates a relay that feeds the power to the window motor......
Far too complex.....
Sort of like bolting a computer to a broom.....Rather sketchy

I have rarely had issues with electric windows in the older rigs.

Yeah the motors can die....But the more they overthink the plumbing the easier it is to plug up the drain......

I would love to find an old square body in good shape.....The 91 Burbs and Blazers were sweet....
The bugs were worked out and there were rarely any issues
Actually....Get back to before the electronic transmissions (TH 400 ERA ) YEAH...Pretty bomb proof...

Ya notice that all the military rigs (HUMMER) They do not have electronic trans or electronic injection.....That says it all....

Just not dependable enough when the going gets tough and ya gotta get outta Dodge in a hurry....

[Yukon6.2]

I need a good blazer to round out my square body collection, of course they are hard to find in any condition here
I do have a project one, rust free but heavily damaged by the drivers door.Arizona truck that got hit hard.I would have to replace the firewall drivers door frame and floor boards,already sitting on a good frame