I paid extra for the anti-spin rear differential. But now I'm not so sure it was worth it. With the ABS equipment applying the brakes to a spinning rear tire and transferring power to the other tire, what does the anti-spin rear diff really do for me?
In my `99 Silverado I could definitely feel it when the anti-slip diff locked up. At the end of it's life, I could feel when it wasn't unlocking, too. But, it didn't have all the electronic traction control the way this '21 Ram does.
The anti-spin diff on 2013+ Ram 1500's is a conventional, clutch-and-cam limited slip differential that engages based upon torque feedback. Same as a "posi" from the 1960s except that the '13+ Ram 1500's don't have any spring preload built in.
The reason they don't have any spring preload built in, omitting that preload prevents the clutches from wearing over time just while driving down the road (example around every corner) and possibly saves a tiny bit of fuel over the life of the vehicle. Because of the traction control system preload is not necessary since traction control will provide the load when it's needed.
Your Silverado may have had a G80 which is an automatic locking differential, not a limited slip. It still uses clutches but it has a pawl that catches a ramp mechanism and it becomes a full lock under the right conditions.
So getting to the question you asked about what good anti-spin does:
simply put it doubles the amount of torque you can deliver to the rear wheel with traction when the other rear wheel is slipping or not in contact with the ground. It also greatly extends the duration that you can continue using traction control before it overheats.
Assuming you know how a differential works, if you deliver engine torque to the pinion (input) of an open differential and both wheels are in the air then both wheels will turn at whatever speed the ring & pinion ratio dictates. If you stop one of the wheels by applying brakes to just one wheel, the free one will spin twice as fast but with half as much torque.
That's what happens when you have electronic traction control (it's called "BLD" in Ram/Jeep products) with an open differential. One wheel slips, traction control applies brakes to that wheel, the other wheel now tries to turn twice as fast but with half the torque.
On a conventional clutch-and-cam limited slip differential when one wheel is given the opportunity to spin faster than the other, preload springs on the clutches cause some drag which forces the spider gear shaft to wedge against cams that apply more pressure to the clutches and this little feedback loop attempts to fully lock the differential. Since the differential is now almost behaving like a spool (to the limits of the clutches) the spider gears are out of the equation and you get full torque to the wheel with traction.. as much as the clutches are willing to transmit.
The anti-spin on '13+ 1500's works exactly the same way except there are no springs pushing on the clutches. The clutches are effectively free and disengaged but the cam mechanism is still there. When one wheel spins faster than the other and it's above the threshold defined by the traction control system's programming, brakes are applied to the spinning wheel. This causes the spider gear shaft to wedge against cams and apply pressure to the clutches and the same feedback loop occurs but with added help from the traction control braking effort. Again this takes the spider gears out of the equation and you can effectively deliver full engine torque to the wheel with traction instead of losing half of it into the spider gears.
Something that may not be obvious; most or all of these traction control systems have a pretty good idea of your brake temperature. It doesn't measure the temperature itself but it has a software model of how much heat the brakes can dissipate and it knows what duty cycle it is applying to the brakes. If you rely entirely on traction control and you're crossing muddy terrain it's possible to overheat the brakes by continuous traction control engagement. Since the limited slip differential is acting in concert with the brake traction control, duty cycle is reduced and can remain in operation a lot longer on the same type of terrain before overheating.