Downhill Assist Control - What am i doing wrong?

so i have a 4x4 tacoma and 4x4 4runner. yesterday i took the 4runner up a gravel road that winds up a mountain. on the way back down, i thought it be a good time to try out the dac and try not to wear my brakes too bad. i stopped, put it in 4w-low, and hit the dac button. i let off the brake and it would go a little and then start to skid and beep at me. the brakes seemed like they were harder to get working also.

should i not do this going down a mountain on a gravel road? i thought steep grades is what it is meant for?

 

i thought i was going by the manual. i guess i'll read it over again

 

If you are in first gear (put the shifter in the "L" setting) and in 4lo, there's nothing more that can be used to slow down except the brakes. Even DAC uses the brakes. Crawl control on Land Cruisers uses brakes, too. It's just smoother.

 

yes listen to these guys. i have a 4runner 4thgen. couldnt figure it out at first but its simple now. but i just dont use it. i rather put it in 4lo and L gear. and use the brakes if i need to

 

On very steep, L4 off road downgrades, it is a very interesting system but it works... It makes clicking sounds and the truck will go down ultra steep grades without sliding. I don't recall having it in 1st gear to work (I am an automatic).

 

it does need to be in 4L. the manual says it needs to be in 1st or 2nd. i tried both, but it felt like i was sliding. maybe it was working, but it felt and sounded like something was wrong, so i took it out of dac

 

Weird noises are normal for DAC and A-TRAC... try them and get used to them. The good part is they both work!

 

Ok. But was it a good idea to use it on steep grade with gravel?

 

All those strange noise are from the ABS firing each corner of the brakes from under the hood. If it's difficult to apply the brakes, or the brakes thump under your foot, that's also normal. Takes a little getting used to.

The way you described it sounds like it was operating properly.

Going down insanely steep grades with loose gravel and stuff like shale, it seems like, are reasons for using DAC. I only use it in situations like those, because that ABS computer can think a helluva lot faster than I can, or if i'm just feeling very lazy.

 

thanks for the reply. i'll try it again on the same road one day and see how it does.

 

this

yes

this

 

DAC is a very nice system. However, it is important to note that DAC will not work correctly on extremely uneven or slick surfaces, mainly because of two reasons:

1) If the tires don't have enough traction to arrest a slide, DAC's braking methods won't work.

2) On extremely technical/rocky downhills, 2-4mph (DAC's target speeds) is too fast. This may be fixable via a re-gear, but for truly technical descents, overgearing, 4lo - 1st ratio with a heavy brake foot is still king. A crawlbox is even better.

DAC is best for steep but smooth downhills of long length - and when it works, it's easier on your brakes and tranny than you ever could be engine braking or foot braking manually.

So it's a good system, but like all these electronic whiz-doos, it has its limits.

 

I cant understand why someone would bitch about another asking a question. Then to say read the manual? Get me a FN break the manual half the time gives a crap explanation. I thought that is what forums were for to help other enthusiasts explain in laymans terms a way forward. Ahh hell what do I know?

 

If DAC doesn't work, then just use the brake (which over-rides the DAC)!

 

well in this case i actually did read the manual - but it doesn't say anything about noise, or feeling like you're sliding, and that the brakes don't work like they normally do while using dac.

but it seems like that is normal, and since i was driving over a mile and half down a mountain, i thought it would be perfect application for using dac

 

The DAC stays at like 2-3 mph... A 1.5 mile downhill taking 30 min. seems a bit long... and is there really a super steep downgrade a mile and a half long? I used the DAC only a few times and that was on short, extremely steep 4WD 'jeep trail' type of roads. The kind of steep that you need to be cautious using the brakes too much because the back end may slide and put you sideways. The DAC is designed to prevent sliding and keeps the wheels turning, but at a speed slower than L4 in 1st gear. It's all for eliminating the need to tap the brakes on these 4WD dropoffs.