Question for those w/ FRONT ARB or Harrop lockers

Question for Tacoma drivers with FRONT selectable lockers:

If you jack your front driver wheel up off the ground in 2WD with locker unlocked, and rotate the driver tire by hand: does it turn your front driveshaft?

Please comment if you have verified this, and specify which brand selectable locker you have in your truck.

(Reason I ask: I have a front autolocker in my Tacoma (Torq), and I am the only one I know with a front autolocker. I recently discovered that the driver side tire is linked the front driveshaft even when the locker is open.

This is unnoticeable in 2WD because the front driveshaft spins freely in the transfer case. However, if I put just the transfer case in 4WD and leave the ADD fork in the 2WD position (by first unplugging the ADD), I will go into “3WD”. This seems to be distinct from trucks with a front differential that has no front locker installed; in that case, if the ADD fork stays in the 2WD position, the truck seems to stay in 2WD when the transfer case is switched to 4WD.

I am waiting to hear back from the manufacturer regarding whether this is normal, and have gotten conflicting reports regarding whether this is also the case with selectable lockers.)

 

What your locker is doing is to be expected.
An auto-locker (when power applied) does not allow either side (axle shaft) to turn slower than the ring gear, so this is why you end up with 3WD (similarly, during coast/no power applied, an auto-locker doesn't allow an axle shaft to turn faster than the ring gear, so is why the driveshaft spins).

I have an ARB, the driveshaft does not spin with the driverside wheel in 2WD (nor can it cause 3WD if the ADD is in 2WD position) because the ARB is same as a fully-open stock differential when not locked.

 

Would it be accurate to say, when power is applied to an autolocker, it will allow neither side to spin slower OR faster than the driveshaft?

(I’m having a hard time thinking of a realistic hypothetical scenario where a tire would spin faster than a driven wheel, but let’s say you are driving down a street that is a solid sheet of ice — it is smooth enough that there is not even enough friction to turn the tires as the weight of the vehicle pulls it down the hill. But you have one front tire of the vehicle on a rocky dirt shoulder. You apply gas to keep the tires on the ice turning slowly, but the slope of the hill accelerates the vehicle body faster than the driven tire speed, causing the wheel with traction in the dirt to — turn faster than the driven tires, or not?)

 

It all depends on what direction each tire (axle shaft) turns relative to the ring gear (the differential itself), and whether the differential is under power (accelerating), or coasting (under engine braking).

Another way to explain it is if torque is applied at one tire (let's say the left tire), the other (right) tire can then rotate freely in an opposite direction, but it can only rotate as fast as the left tire going in the same direction (same speed as the ring gear). This ability to turn opposite is what allows you to make turns without the tires scrubbing against the ground.

You should be able to demonstrate this for yourself by having the truck in gear (in Park or 1st) (ADD also locked) and both tires off the ground...
If you attempt to rotate one tire (let's again say the left tire), the differential will lock, and not allow the tire to rotate because the ring gear itself is prevented from turning by the driveshaft (truck is in gear).
While holding pressure on the locked tire, you should then find that the opposite (right) tire will rotate freely in a direction opposite of how you are holding pressure on the left tire, but it cannot be rotated in the same direction.

If you switch tires and/or directions, you will again find the same (the left tire will rotate freely in the direction opposite of pressure held against the right tire, for example).

If the ADD is unlocked (in '2WD' position), the driverside axle and ring gear will always spin as one because there is never any input (or output) torque at the passengerside at all.

In your sliding-on-ice example, the tire in the dirt would actually be prevented from turning faster than the other tires, and could cause the truck to veer off course on the ice as well.
Ice is a tricky situation for any traction-aiding differential, especially an auto-locker... If one tire catches traction, then that tire will be the one to receive all the torque. This is why you might hear some say that an open diff is better in extremely slippery conditions such as ice... If one tire catches traction with an open diff, little-to-no additional torque will be sent to that tire, lessening the chance of veering out of control.

That help?

 

It's accurate to say one wheel cannot spin SLOWER than the ring gear. The situation of a tire spinning faster than a driven wheel is not just hypothetical and is very realistic. In fact, it's how the locker operates every time you turn. In a turn the outside tire is overrunning the carrier and the ring gear is matched to the speed of the inside tire which is receiving all the torque. If you apply enough throttle and slip the inside tire enough it can "catch up" to the outside tire and then lock the axle entirely to the same speed. This is the feature that differentiates an auto locker from a spool.

How you describe your locker working is exactly as would be expected.