I have a 2006 tacoma 4x4, the differential lock won't engage probably from lack of use. Is there any way to manually free up the lock? If this can't be done, how do you pull the diff lock

check that the clutch is fully engaging by checking if there is free play at the throw out lever and clutch push rod . If you cannot push the rod back into the cylinder then the slipping is because the clutch is only partially engaged. Replace the clutch master cylinder if that is the case. If it is right then the fault will be in the pressure plat/ cutch plate and it may require a clutch kit.

Ok I know this question is old but for any one else who has this problem, I want to clear some info up. GM did not use vacuum on the 4x4 systems on the full size series. Only used on the S series (S10, S Blazers). Here is how to accurately trouble shoot these problems with the full size 4x4. Remove the front actuator from the front axle ( keep it plugged up and let it hang). Put the T-Case in 4x4 Hi or Lo doesn't matter. Turn key on (don't start the engine) . Now check the actuator to see if it has extended. If (no) now check the plug to see if you have current . If you have current to the plug, change the actuator. Problem solved. If no current to the plug. Check for broken wires ( fix if any) If no broken wires. There is another switch on the T-Case that sends power to the actuator Replace it.. Back to the actuator.... If everything checked out and actuator works. With the T-Case locked in 4x4, try to turn the front drive shaft by hand. With the T-Case locked in 4x4 you shouldn't be able to turn the drive shaft. If drive shaft doesnt turn the T-Case is in good shape and the problem will be in the front differential. In these cases the most common problem is an exploded thrust washer. At this point the front differential needs to be rebuilt. Back to the T-Case..... With the T-Case locked in 4x4, if the drive shaft spins, the problem will be in the T-Case and at this point the T-Case will need rebuilt......... I hope you get the information you need to troubleshoot the GM 4x4 issues.

front differential has a electronic modulator / actuator it engages / lock in front differential they burn out frequently I bought a manual one from my local 4X4 shop no more problems

Quadratrack transfer units work by way of an internal fluid coupler (same as your mechanical clutch fan but bigger) It is always on but not always engaged. It engages when the rear wheels start to slip.
It should lock in low range though. (in low range you should not drive over 15mph).
if the front wheels won't engage at all, then either there is something wrong inside the transfer case or inside the front differential. Both are usually noisy if they have failed but I've seen some that the ring gear has been removed as well as the driveshaft (sometimes) after the diff has failed, so it can be driven. Find another shop that's more familiar with that unit and have them take a look at it if you don't see anything obvious.

Other than the oil change I would recommend replacing the spark plugs, change the coolant, air filter, cabin air filter, rotate the tires and check brakes, change transmission fluid and differential fluids and transfer case if 4x4.

There are actually two actuators, one is located in the transfer case and one on the front differential. the one on the transfer case provides power to both front and rear driveshafts, the front actuator must engage so that the front differential locks and provide traction to the front wheels. This means that even if the transfer case is engaged in 4x4 mode the front wheels will not have traction if the front diff actuator is not working.

could b a number of things


actuator on rear end no vacuum going to the actuator switch bad etc......

if its not leaking do not touch it. its lifetime.

there is a vacuum port on the front differential acuator if you have acces to a lift apply vacuum to the port until it pulls the differential into 4 wd its probably just stuck from lack of use or try TAPPING it with a hammer not HAMMERING it

more than like have a broken axle shaft, un hook the rear drive shaft and put it in 4wd if it wont move then you know you got a broken axle shaft or spider gears broke in the pumpkin