These are 2 completely different things!
Did you check in the instrument panel window?
There is shows clearly when all 4 wheels are powered and when not. That will answer your question once & for all.

 

The AWD is full time on every RX, including your 2010. Locking the "centre diff" on the 2010 is only allowed up to 15 mph, but AWD is always active.

It sounds like some people here are trying to define full-time AWD as something it isn't. Full time AWD does not mean that you have torque going to every wheel all of the time, it just means that the AWD system is always on and not user selectable like a part time 4WD system (such as is used in a truck like the Tacoma, where it is always 2WD or always 4WD depending on what you select).

The RX is always AWD and pushing the lock button temporarily fixes the torque ratio at 50/50 for low speeds.

Jeff

 

Further to what Jeff said - don't know if all models have the dash indicator showing how much power is going to each wheel but mine does. As you drive along with little/no throttle drive is to the front wheels only, push the throttle harder and you can see the rear wheels get some power, try alternating between little throttle and hard throttle, lights up rear wheel indicator as you move the throttle.

As Jeff said the system is ALWAYS active, waiting to be used when required, sure driving along the freeway it's only using the front wheels but it's ALWAYS waiting for the times when traction is less and it will then put some power to the rear wheels as well. And the switch to "turn on" AWD just forces the system into all wheel drive at slow speeds.

Someone said their car slips in the wet, I've tried mine on gravel roads, from a stop hard throttle and she just bites and goes, no loss of traction.

 

That shows how the OP doesn't understand the system, that slippage is due to tires and the amount of power he applies.

 

I see some RX's listed as 4WD, some as AWD. What's the difference for RX350's?

 

The difference as I understand it is that AWD is always in 4WD whereas 4WD must be put into that condition manually.

 

The RX is AWD. You see them listed as 4WD sometimes, but that's because people writing the listings don't know the difference, or don't care.

All-wheel drive

As the name implies, all-wheel drive (AWD) feeds power to each corner. Depending on the system (designs vary), AWD can provide maximum forward traction during acceleration. It is especially helpful in sloppy road conditions and when driving over moderate off-road terrain. It can help get you going and keep you moving through mud, sand, and other loose surfaces. Most AWD systems deliver power primarily to one set of wheels, front or rear. When slippage is detected at one axle, power is diverted to the other axle, in hopes of finding more traction there.

Not all AWD systems are equal. Subaru’s AWD system always directs at least 20-percent of the engine’s power to the rear, and it can direct a larger amount aft if needed. Many other systems fitted to front-wheel-drive vehicles operate with 100 percent of the power normally going to the front wheels; the rear wheels then only receive power only when the front wheels start slipping.
AWD systems are especially helpful in rapidly changing conditions or when driving on a road with intermittent snow and ice. It is commonly used for car-based SUVs, as well as certain cars and minivans

Four-wheel drive

Although four-wheel drive (4WD) and AWD are designations that are often used interchangeably in advertising and sales literature, there is a difference. Generally, 4WD is optimized for severe off-road driving situations such as climbing over boulders, fording deep water, and tackling steep hills with loose, low-traction surfaces. Most 4WD systems have high and a low gear range, the latter used to increase low-speed climbing power. Some have differentials (which allow left and right wheels and front and rear axles to turn at different speeds) to be locked for maximum traction.

Modern 4WD systems are either full-time, which means they stay engaged; automatic, where the vehicle automatically switches between two- and four-wheel-drive mode; and part-time, which require the driver to manually shift between two- and four-wheel drive. Vehicles with a part-time system shouldn’t be driven on dry pavement when in 4WD mode, which could risk damage to the vehicle's drivetrain.

Aside from serious off-road enthusiasts, most drivers never come close to needing the capability that 4WD systems provide over and above AWD systems.

 

Sorry but this is not correct. Though the lines have been heavily blurred, there is a distinct difference between 4WD and AWD.

4WD: All four wheels spin at the same rate when 4WD is engaged.
AWD: Torque is transferred to the rear (or front in some cases) when slip is detected. Even so, all four wheels do not spin at the same rate. Even having limited slip differential (LSD) will not make them spin at the same rate.

RX is not a 4WD vehicle and uses a center diff to engage the rear wheels when slip is detected in the front wheels. But only under 25mph. Please feel free to add corrections as this is always a debatable topic.

 

Not true. AWD does not power each corner independently.

This is true. AWD does the front to back. It does not do side to side, which is the responsibility of LSD. RX may have a brake-based LSD system but no diff.

 

Youtube Video:

 

It really depends on context and terminology.

4WD isn't inherently specific to one type of driveline, just like AWD and 4x4 aren't, though they have common usage.

When most people say AWD, they mean full-time 4WD. When most people say 4WD or 4x4, they mean part-time 4WD. The specifics of how each system within those also vary. Full-time and part-time 4WD are I believe the least ambiguous terms. The difference generally is that a full-time 4WD system will have a centre differential and a part-time 4WD system won't. A system with a centre differential can be driven on all surfaces without any binding due to front/rear wheel speed differences, however it can be detrimental in certain low traction/off-road situations. A part-time system is typically driven in 2WD mode, but can be engaged to provide equal torque to the front and rear wheels, even during wheel slip.

With that in mind, the 2010+ RX is an electronically controlled full-time 4WD (or AWD) system that does not use a centre differential. The transfer case directly drives the propeller shaft going to the rear differential at all times. The function of the centre differential is replaced by the use of an electromagnetic wet clutch system mounted on the input pinion shaft of the rear differential. Without control power applied, the propeller shaft is not connected to the rear differential and so torque is only delivered to the front wheels. By varying the applied voltage to the coil, the clutches can be progressively engaged until they are fully engaged, providing a locked front/rear bias. When not locked, front/rear wheel speed differences are absorbed by the clutch pack.

Each vehicle can and is often slightly different in how it implements a 4WD system. You can have a vehicle with a part time transfer case and front and rear differential lock that will be providing 25% of engine torque to each wheel. You can have an AWD vehicle with three Torsen LSD's and be providing 100% of torque to a wheel that is slipping. There are vehicles like the 2003-2009 4Runner V6 that have a multi-mode transfer case, allowing RWD, full-time 4WD (AWD), part-time 4WD (locked centre diff), and a selectable low-range, when equipped with a rear differential lock (as is used in the 2009 4Runner Trail Edition), it provides a very selectable driving experience for whatever road conditions you encounter.

The new RAV4 on the other hand provides four-wheel electronic torque vectoring. It further removes both the centre differential and the rear differential and uses 5 of the electromagnetic couplings, one at each wheel and one at the transfer case output to control torque output individually to each wheel. The 5th clutch is used to reduce frictional losses by eliminating the propeller shaft from rotating when 100% of torque is being used by the front wheels.

There are plenty of other systems out there as well, all with pros and cons. Some more simple, some more complex, some better, some worse. In the end though, they're most often still able to be described as either full-time 4WD or part-time 4WD.

Jeff

 

My wife just traded in an older 2012 RX350 AWD for a new 2021 version. We have just received our first snow in the Seattle area with I'm sure more to come. Under what driving conditions do you suggest the following procedure? How much snow do you need for this and are there any reasons not to activate this procedure?

 

I push the button but no extra light turn on.

 

(1) Do you have an AWD unit?

(2) At what speed did you push the button?

(3) Have you read the manual, about how the "Lock" function works?

(4) Your info block says you are in Florida. Why would you engage the AWD lock function in Florida?

 

He went off road on Alligator Alley and now he's stuck in mud😀