What mechanically is actually going on behind the dash? Obvi the brakes and accelerator are being applied, but there seems to be a LOT more going on.

A lot of the noise is the ABS system pulsing the brakes. I wouldn't say all of it, but a lot of it is.
You get used to it. The first time I used crawl control I really didn't like the noise. A few more times, and now I hear it, but kind of ignore it.

The noise is a combination of things, but primarily you're hearing and feeling the brake booster pressurize the braking system and then the solenoid valves (electronic hydraulic valves) open and close in rapid succession. That combined with the shuddering that happens from the brakes that results from that rapid application and release of braking at each corner combines to give you crawl control noise/feel. There is a lot going on inside the master cylinder at one time and it's quite a complex unit do function as it does. You'll notice that it's much less harsh in the higher speed settings. I think a future advanced version will being to move from a binary application where it's on or off at each brake circuit to some sort of continuous variation in pressure so the system would operate smoothly and quietly but have the same effect. That's what I'd expect to see in a next generation version. Possibly with more integration of things like skid turning and front dig capability like the land cruiser has some early versions of.

2022 4runner with 2100 miles, tried crawl control for the first time after reading manual and watching youtube vids. In grass and loose grave drive. Grinding, expect from left front drive...this can not be normal...grinding, I can not expect this to be normal. Plan to visit my dealer tomorrow for explanation. I have owned many 4x4 and understand the expected normal sounds, grinding means gears are not meshing...result, metal filings.

There is definitely more going on.

This isn’t just smooth cruise control braking. This is actual noisy ABS style braking that occurs when you would otherwise skid.


Sent from my iPhone using Tapatalk

It's normal. There's no disconnect on the driver side and we do not have locking hubs.

The majority of the noises you hear is the ABS system actuating solenoids, the brakes grabbing the rotors sharply, and the drivetrain alternating between having a little slack and taking that slack up. It's likely normal operation, particularly if it's the driver's front area given that the majority of noise comes from the ABS unit itself.

You say you've owned many 4WD vehicles, but have you owned any with systems like crawl control or A-TRAC? This is old hat for anyone who's owned a 4th/5th Gen 4Runner, FJ Cruiser, 2nd/3rd Gen Tacoma, 2nd/3rd Gen Tundra, and/or LC100/LC200. They've all been noisy and sound like they want to blow apart when A-TRAC, Downhill Assist, and/or similar features engage.

Make sure you have the volume up when you watch those YouTube videos again. You’ll definitely hear the ABS actuators running in the background.


Sent from my iPhone using Tapatalk

Yup. Normal. Crawl control, Downhill Braking System and the A-Trac all use repeated pulsing of the brakes.

The 'grinding' noise you hear is from the brakes being applied and released repeatedly
by the 'fancy electronic' brake system.

If you are used to old time traditional 4 wheel systems, the grinding/bumping is not a good noise.
But in this case, it is perfectly normal.

When I first got mine and was playing around with crawl, I got the brakes pretty hot, for what i thought was a short period of time. I guess not short enough. Cool feature.

Nice synopsis but I think you are way too optimistic. We are talking about the company who is using the same 5 speed transmission from 20 years or so ago and is celebrating the 40th year with a colorful decal.

Crunch..grind..crunch.. grunt.. grind..

Yeah its working normal!

Eh, I mean the A750x was/is damn solid transmission, probably one of the best Toyota/Aisin made. Given how many ZF transmissions seem to have issues, so much so there's rumblings about multiple class action lawsuits because of it; I'll take a 5spd that will easily last 200k+ vs. a needless number of gears for the sake of marketing.

Thanks to everyone that replied. I have one question, do wheels have to lose traction in order for alternating breaking to occur? Because testing system in lawn grass it sounds like it is trying with no wheel spinning. Thanks for your input.

The ECU definitely has to see a difference of speed between the wheels to actuate which is why it falls short or a locker.