Crawl Control failsafe?

Greetings intrepid friends.

In another thread discussing the 4Runner’s various off-road features it was noted that under severe use Crawl Control will disengage to keep the ABS system from overheating. An astute reader asked the type of question that’s only obvious once asked:

What happens if the Crawl Control system shuts itself off
in the midst of a descent?​

Do the brakes lock up? Does the system give some sort of warning? Or do the brakes just let go, plunging you and your truck to your doom?

Has anyone here ever pushed your Crawl Control to the point that it shuts off? What happens?

 

I don’t have CC on my SR5 but I have Downhill assist. I’ve only used it once, didn’t care for it. I prefer to use 4L and 1st gear (engine braking) when descending a steep hill.

 

I'm going to assume it gives you a warning and you have to jump on the brakes to keep yourself from rolling. The brakes don't overheat, the ABS pump does.

 

Good question! I'd like to think it would apply the brakes and give you a warning, but I hope I never find out.

I've tried it a few times, and it generally goes too fast for anything I'd want to try it for.

+1 for this. I prefer 4lo/S1 for a steep descent. And, I always tell newcomers to do the same when we're on a trail run.

 

That's why I've always considered these electronic systems, gimmicks.

 

I agree with both of these posts, but I feel that the 4Runner’s gearing is too high and the compression too low to rely on engine braking to navigate a steep descent. Which means a foot on the brake pedal, which brings us back to ABS-based descent control.

 

I think it is a cool concept. But, I think it could be executed better. I think part of the issue is that we don't have a low enough crawl gear in the 4runners for it to be very effective.

Multi-terrain is probably more beneficial, but either way, I do like the idea of using the ABS to control wheel slip.

 

Haha, I think we are on the same page today.

I wish Toyota would give us a better 4lo ratio.

 

Agree with the general premise and prefer driving skills to electronic nannies.................except
in a case where stupidly put myself in harms way (decending snow covered granite with little margin for error and likely outcome a rollover), learned that crawl control has a couple tricks up its sleeve that no amount of skill can duplicate. Specifically, yaw control/ability to brake individual wheels when nannies sense an upcoming front to rear swap. Concede the racket the system spews while engaged is......uhh......distracting and a ½ MPH low setting would be ideal. Also concede I'd have been Fubar'ed without it.

 

That's very interesting! Thank you for sharing.

 

For some perspective, let us harken back to the olden times and look at the predecessors of Crawl Control. Before ABS, descending a steep incline with challenging traction issues was problematic. If the vehicle had a low enough crawl speed the descent was somewhat easily controlled. But any application of the brakes came with the risk of locking up the wheels on the slippery surface. With the vehicle now sliding, steering inputs were meaningless and the driver’s only chance of regaining control was to gently pump the brakes, which resulted in an increase in speed and momentum, resulting in even more risks.

The first vehicle I owned with ABS traction control was a late ‘90’s Discovery with “Hill Descent Control” and I was pleased at how well it worked on a nearby trail on a descent typically carpeted with pine needles. The idea was that the vehicle would slowly descend in such a way that that the wheels would never lock up, and even if they began to slide there was always some measure of steering control.

Having grown up with old school 4WD vehicles, like many of you, I am frequently quick to eschew all the nanny stuff. But I must admit that descent-control devices can perform some tasks with an ease unachievable even by highly skilled drivers.

 

I agree that the systems aren’t a total gimmick. They can do things with the truck that we simply can’t replicate…. Lifting itself out of deep sand is an example. I haven’t tried it myself, but I’ve seen videos. There’s more going on here than simple brake/accelerator/steering input.

 

This gentleman did a great job of demonstrating the down hill assist system. Although I prefer engine braking, on slick rocks the DHA may have the advantage to control tire slippage. My experience was on loose gravel and dirt which is different than smooth rock as shown in the video.

https://m.youtube.com/watch?v=uMe5Vt9PnLE

 

I’ve tried both Crawl Control and 4LO/1st on the same very steep hill with loose rocks and I felt a lot better with CC engaged.
CC is a lot better than a lot of people think it is IMO

Like others have said, our gearing is not good enough to just be in 4LO/1st without using the brakes. If we had something like the Marin crawler tacobox it would be a complete different story

 

Yeah, our crawl ratio is only (aprox) 33:1, which is definitely nothing impressive. A Tacobox would definitely help! I've watched a few of the Marlin crawler videos, that thing is super impressive.

For comparison, a while back I was interested in Land Rover LR3's, they have a 45:1 crawl ratio.

 

We all make our compromises. Coming here from a decade of Wranglers (don't start.....), my expectations were a significant decrease in offroad ability offset by a more civilized almost everything else experience. Our fully locked Rubicon was the blunt instrument that provided my cover for taking bad lines, etc. The reality of our 4R is that it's surprisingly capable if I actually engage the thing in my skull before the 4Lo lever. Won't ever be a Rubi, but a heck of a lot closer that I imagined. Except for the 18 hour drive to and from Ouray. The day it reminds me of a lifted 2 door Jeep on 35's on the highway is the day it goes on the block.

 

The original question was based off relying on a mechanical locker used over time vs CC or A-Trac used over time and how CC or A-Trac may be idiot proofed and turn off automatically (I hope not).

I guess the concern is the ABS pump and it over heating if using CC or A-Trac over time. I would assume CC should work as long as you need it with no shut off because that would be really really bad if being used in a descent and it just turned off.



99% of the time regular 4L will do the job, but CC can certainly help with a rocky decent and you can control the speed, plus get you out of some really stuck scenarios. So I wanted to be sure CC didn't just stop working.

 

I haven't experienced it myself but I'm assuming you get a warning as temps creep up. The foot brake is the backup.

 

You’re probably right. But it would be interesting to know. Maybe one day I’ll take my 4Runner to a long steep road, like Roscomare Road or Encino Hills Drive, and crawl down on crawl control. Either of those streets is 3 times longer than any technical descent I’ve been on.

 

My guess is, that the ABS traction aids are engineered so their useful duty cycle is greater than the average off road loose traction encounter.

 

I’m in Socal too. I remember an old post where a Runner Trail ATRACed his way up a pretty gnarly trail and it overheated on him multiple times so they had to stop until it cooled off. They eventually made it but I think he ordered a locker the next day.

 

Lol, so long as it’s been verified to work. I struggled just to get the emergency brake to work well enough to hold it’s own weight on my driveway with a very mild slope. Now that I’ve spent some time adjusting cables it does fine stopping the vehicle on flat ground from about 25mph. I dont think it would slow you down that well of it’s already rolling down a steep hill.

Some good comments on here about CC and DA, and positive aspects I hadn’t considered. But In high-danger situationd, I have a hard time relinquishing control to a system if I don’t completely understand how it operates. These aids seem to me to be more like training wheels. Which is fine, but I would rather be the one managing energy on a steep slope.

 

Foot brake meaning the brake pedal, not the parking brake.

 

Ah, I figured overheating would include brake fluid that’s gotten too hot as well (possibly boiling out moisture). But yeah, I’d hope everyone is covering the brake pedal when using CC or DA!

 

I get this line of thinking too. Personally, I would never approach a line that I thought I couldn’t handle myself and then hand it off to the “crawl control” system. That just seems dumb and potentially dangerous.

But I would play around with the system in spots I knew I could handle on my own and then see how the systems handle it and if they do better than me, I’d use them again.

 

So now that you have experienced manual driving vs CC, what are your thoughts regarding the CC performance?

 

I honestly have very little experience with the systems in recreational or “shit hits the fan” scenarios. I’ve played around with them in snow, super bumpy fields, and low maintenance roads just to familiarize myself with how the systems function in case I ever do find myself in a bit of a predicament.

I’m not a recreational off-road guy. My truck is a tool. And I see the crawl control systems as a tool, too. Might the tool come in handy sometime? For sure.

I also think it’d be fun to go out off roading and use the crawl control as a “toy” and a lot of guys probably do that. That’s cool too.

 

Sounds good, I agree, adding tools to your toolbox is a good thing even if you only use it once in a while. I don’t off road just to off road either, but in support of my hobby.