GX550 Premium, only front left wheel and back right wheel spins (1 Viewer)

[sunnyday]

Hi, noob question here.

Today I got stuck in sand with gx550 premium.

I enabled L4, then pressed the button with wheel lock.
But only two wheels spun: front left wheel and back right wheel.

I wanted all 4 wheel to spin.

What did I do wrong?

 

[bart]

Likely nothing, that’s how open differentials work - torque “chooses” the path of the least resistance so it goes to wheels with less traction. Non-overtrail models only come with a central locking diff - when engaged power is split 50-50 between front and rear axles, not between left and right wheels on either axle.

That said, even non-overtrail GXs come with Toyota A-TRAC system which applies breaks to wheels with less traction, when it senses slip, in order to send power to the wheels with more traction. That system supposedly engages when the track is put in 4Lo, and, from what I heard (never actually tried myself), is pretty efficient - locking diffs should not be needed unless in very hard, rock crawling conditions.

 

[sunnyday]

Likely nothing, that’s how open differentials work - torque “chooses” the path of the least resistance so it goes to wheels with less traction. Non-overtrail models only come with a central locking diff - when engaged power is split 50-50 between front and rear axles, not between left and right wheels on either axle.

That said, even non-overtrail GXs come with Toyota A-TRAC system which applies breaks to wheels with less traction, when it senses slip, in order to send power to the wheels with more traction. That system supposedly engages when the track is put in 4Lo, and, from what I heard (never actually tried myself), is pretty efficient - locking diffs should not be needed unless in very hard, rock crawling conditions.

Thanks! This clears up my confusion.

If I wanted my wheels to actually spin on the wheel that touches the sand, do I turn on the wheel lock? What about L4?

 

[bart]

I don't actually do any offroading - don't have any practical knowledge. I only understand how the mechanics works.

When it comes to "controlling" which wheel gets torque - you don't have such control in non-overtrail trims. In overtrail you'd lock the rear diff and both wheels would rotate at the same speed. In non-overtrail the only thing that "simulates" that is a-tract - traction control will apply break to the wheel that is slipping in order to send power to the other wheel.

What does 4L do - it multiples the torque. More torque going to the wheels for the same engine output. In practice it has two effects

• fine throttle control at very low speeds. In H4, even the smallest blip of the throttle translates to a relatively large surge of wheel movement. In L4, that same throttle input produces much less actual wheel rotation, so you can creep over rocks, through ruts, or down steep descents with surgical precision without the engine "jumping." It's the difference between trying to do detail work with a power drill vs. a screwdriver.
• the engine can pull through resistance it couldn't in H4 — deep mud, steep climbs, sand. Without the torque multiplication you'd either stall or have to rev the engine hard (which kills traction control's ability to manage wheel spin).

What does central lock do - it locks the transfer case so that each axle gets exactly 50% of the torque. In practice that is useful when wheels on one axle are slipping and both wheels on the other axle have traction.

I don't know why didn't you get unstuck - why the a-trac didn't help. The GX manual is a little convoluted. In some places it means "Active TRAC" and "VSC" together in some it doesn't... Maybe switching to 4l and locking center actually disables a-trac . Manual says

When the four-wheel drive controlswitch is in L4 with the center differentiallocked, VSC is automatically turned off.(The center differential lock and VSCOFF indicator lights come on.)

But then in the section about "Active TRAC" and "VSC it says

Disabling the Active TRAC system ... “Traction Control Turned OFF” will be shown on the multi-information display. Turning off the ActiveTRAC/VSC/Trailer Sway Control ... VSC OFF indicator light will come on and the “Traction Control Turned OFF” will be shown on the multi-information display.

My guess is this means that 4l + center lock don't turn off Active TRAC, but I don't know. Did you see both “Traction Control Turned OFF” and VSC OFF indicator light?

 

[sunnyday]

I don't actually do any offroading - don't have any practical knowledge. I only understand how the mechanics works.

When it comes to "controlling" which wheel gets torque - you don't have such control in non-overtrail trims. In overtrail you'd lock the rear diff and both wheels would rotate at the same speed. In non-overtrail the only thing that "simulates" that is a-tract - traction control will apply break to the wheel that is slipping in order to send power to the other wheel.

What does 4L do - it multiples the torque. More torque going to the wheels for the same engine output. In practice it has two effects

• fine throttle control at very low speeds. In H4, even the smallest blip of the throttle translates to a relatively large surge of wheel movement. In L4, that same throttle input produces much less actual wheel rotation, so you can creep over rocks, through ruts, or down steep descents with surgical precision without the engine "jumping." It's the difference between trying to do detail work with a power drill vs. a screwdriver.
• the engine can pull through resistance it couldn't in H4 — deep mud, steep climbs, sand. Without the torque multiplication you'd either stall or have to rev the engine hard (which kills traction control's ability to manage wheel spin).

What does central lock do - it locks the transfer case so that each axle gets exactly 50% of the torque. In practice that is useful when wheels on one axle are slipping and both wheels on the other axle have traction.

I don't know why didn't you get unstuck - why the a-trac didn't help. The GX manual is a little convoluted. In some places it means "Active TRAC" and "VSC" together in some it doesn't... Maybe switching to 4l and locking center actually disables a-trac . Manual says

But then in the section about "Active TRAC" and "VSC it says

My guess is this means that 4l + center lock don't turn off Active TRAC, but I don't know. Did you see both “Traction Control Turned OFF” and VSC OFF indicator light?

Thank you for the detail. Learned a lot!