Hi, Just thought I'd share this problem with other members. I tried to push the lever over to Diff lock the other day and it was seized solid. No amount of brute force would shift it, so I started to undo the 4 screws holding the centre console in - 2 at the front and 2 in the cubby box.
Unsrew the gear ***** & gaitors.
Take the clip off the handbrake pin and remove the pin.
Now carefully lift out the console.
There is a rubber cover with a metal band around, fixed in place with rivets.
Drill a few 3mm holes about 20mm away from each rivet (Required for re-fitting with self tapping screws).
Now drill out the rivets and gently lift the rubber cover and metal band.
You are now looking at the top of the gear box.
Undo the variuos nuts, bolts & clips on the right hand side of the hi/low gear stick.
Use an 8mm/10mm socket to remove the 4 bolts that hold the hi/low gear stick box to the main gearbox.
Take the box and look at the shaft running through the centre, spray with WD 40 and let it soak.
Take the plate off the top and position the whole box over a vice with just enough room for the shaft to fit through the vice gap.
Use a solid rod the same size has the shaft and hit the shaft with a heavy hammer until the shaft moves.
Once you've gained access to the shaft, clean with wire wool and grease all the moving parts.
Put it all back together and operate the Hi/Low gear stick at least once a week to prevent it seizing in the future.
Hope this will be of some assistance to other members.

 

The procedure for disassembly will be useful. But my shifter isn't mechanically seized. Instead, it sometimes shifts into low very smoothly, and other times won't budge. It always shifts smooth between locked and unlocked. I think the problem is the lockout-solenoid is preventing it from shifting into low. That could be because the solenoid for the lockout pin is faulty or the switch on the transmission that activates the solenoid circuit when in neutral is faulty.

It seems to work fine when everything is cool (been parked for 10 minutes). But in the process of driving, I go to shift into low-gear and it refuses. I try rolling back and forth, rocking, shifting around searching for a lever position that will unlock it and it just stays stubborn. If I get out, kick the tire, and walk away for 10 minutes, come back, it will shift like butter. I hate that because it it's like it's not quite broken enough to make me want to tear it all down and do something about it.

 

Thanks for that write up Growlinbear. I had a U joint blow up a couple weeks ago on my front drive shaft so I removed it and put my truck in Diff Lock so I could get by until my new one arrived. It took a lot of force to even get into Diff Lock. After I installed the new drive shaft, I couldn't get out of Diff Lock, my shifter just wouldn't budge to the right. I followed your process and got the console and shifter out and it was full of some nasty grease that had hardened into red glue. I ended up dismantling the entire CDL shifter and cleaning/re-greasing. Works like a champ now. The only thing I did differently than you was I made the existing holes slightly larger on the trim ring for the rubber cover, then got sheet metal screws that fit the existing pop rivet holes. Thanks again.