Searched everywhere and did some real world testing.

Buddy just scored an 04 SR5 for $1k! 200kmi but in great shape. Anyhow... trying to figure this new fangled "center diff lock" gizzmo out.

So the vehicles always in 4wd/AWD?

There's a viscous differential between the front and rear drive shafts?

The center diff lock "lock" above mentioned differential?

So I had him attempt to crawl it up on a boulder in my yard with the passenger side front. As soon as the suspension was limited the pass rear started spinning but the fronts were almost motionless... looked like they were trying to put down a little power but no where near the same 5-10mph speed the one rear was spinning. He hit center diff lock and boom, fronts turned at same speed as rear and up he went at crawl speed.

He thought he scored a rear E-locker like my 97 but thats no the case. Either way it was $1k, runs and drives perfect. Possible head gasket but we'll cross that bridge when...

Thanks!

Pretty much disables vsc and gives 50/50 power to front and rear.

First off, is it a V6 or a V8? The V6 has a "Part-Time 4WD" system that lets you shift it into 2Hi. The V8 uses an "All-Time 4WD" which means the vehicle is always in 4Hi.

Both front and rear differentials are open, the center uses a Torsen T3 torque-sensing differential that is lockable. In the unlocked position the T3 will bias torque as it senses fit (it allows the vehicles to drive very comfortably in 4Hi without the typical binding you'd find in say domestic 4WDs), but it's got limitations as you noticed when you got one wheel to lose traction. Locking the Center Differential (the transfercase actuator moves the shiftrod and locks it) gives you a 50/50 power split to the front and rear axles. From there you still have open differentials front & rear so ATRAC is supposed to help mitigate that.

I would get the owner's manual for the vehicle if you can, it's got lots of good info. But yes, you used CDL the way it was intended.

Hopefully this can elaborate on the topic. Essentially the V6 & V8 have the same system other than the V8 is setup to be AWD all the time without option for 2HI/RWD like the V6 can do.

V6:
2WD - unlocked (RWD); 4WD - unlocked (AWD)/locked (4x4); 4LO - unlocked (AWD)/locked (4x4)

V8:
4WD - unlocked (AWD)/locked (4x4); 4LO - unlocked (AWD)/locked (4x4)

When the center diff is left alone and unlocked this is most commonly referred to as AWD. If the diff is locked it usually then referred to as 4x4. The 4th Gen 4Runner can function in any drivetrain mode without the diff locked until the user commands it to be locked by pushing the button on the left dash panel.

This is an exceptionally versatile system. For example, 4Lo can be used unlocked. One example that is nice about this feature: I've used this mode when extracting a watercraft from a boat ramp. Being in 4Lo unlocked allows greatest torque application for extraction and more controlled throttle and speed. Also allows ability to maneuver around the boat launch without drivetrain bind until in a good position to select 2Hi or 4Hi.

Few other manufacturers have implemented a system like this. In fact, the only other 4WD system I can think of like this is the Mercedes-Benz G-Wagen.

Got it, thanks guys! It's the v6

The only other thing to note is that while the V-6 is a "part-time" 4WD system, it does have a limited slip diff and can therefore be driven on all surfaces safely without binding. This is markedly different from other part time 4WD systems (like the 5th gens), which lack the LSD. Those systems cannot be used on dry pavement, or you risk ruining the transfer case.