HDC query

Hi all, quick question regarding the operation of HDC, I couldn't find a match on a search so here goes, never having used it before I selected HDC this evening and pulled away in first gear, without any throttle I could hear odd noises from the transmission (or could have been the ABS), it was on flat level Tarmac and as I say no throttle or braking, I'd assumed the car would just roll along as normal but can anyone shed any light on this?, sorry if I'm being a bit vague.

it won't accelerate the car

only apply the brakes



you need to be pointed down a................hill, for it to work

Sorry yeah I realise that mate but I wandered what the odd intermittent noise was, as I said it was on level Tarmac and just running on tickover

britishwardog said:

Sorry yeah I realise that mate but I wandered what the odd intermittent noise was, as I said it was on level Tarmac and just running on tickover

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mine makes a right racket when in hdc and always has, i'd assumed that is was a normal feature. sounds like a gear type rattly sound.

Lol, yeah that's the noise!, cheers for your help

no worries anyway it's normal so don't be alarmed

i found out it's the abs pulsing that causes the noise

If you use HDC on a steep hill, you can hear and feel individual brakes snatching on.

Must admit I didn't expect to hear anything in a situation where there wouldn't be a need for braking :-/

i found the noise to be reassuring when i first engaged it on Hard Knot pass

The hdc will not go over 5 mph that's why the brakes engaged and made noises.
It also works great uphill if on ice/snow. And on levelish ground if in deep mud or on a pebble beach etc. In fact if you get stuck just switch it on and engage first, it's never failed to pull me out of what I'm stuck in yet.
Cheers
Mike

Good stuff! Cheers guys!

I had mine on permanently this weekend when not on Tarmac.... It is brilliant. It works at a slightly faster speed than a P38 or Defender 90 when going down steep hills, so you need to keep plenty of distance between you and the vehicle in front.

I had it on when wading and just let it chug through in 1st on idle. No sweat.

Skinny Mike said:

It also works great uphill if on ice/snow. And on levelish ground if in deep mud or on a pebble beach etc. In fact if you get stuck just switch it on and engage first, it's never failed to pull me out of what I'm stuck in yet.
Cheers
Mike

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Err, not sure how that would work then, as the system applies the brakes to whichever wheel it senses is going faster than the target speed, but is disabled as soon as you touch the throttle pedal, or the brake.

HDC is designed for going down hill to maintain a constant low speed, but with feet off the pedals

NOW:

Traction control would certainly help and cause the effects you describe, but does not require switching on

I've never used the HDC on my Freelander, in fact like lots the wire's broke off the switch and I've never put it back.

But I was chatting to an Aussie fella sitting next to me on a plane once and he was saying that he doesn't trust the HDC on his D2 after it lost the plot going down a slope once so just turned itself off and resulted in the car going into freefall down the hill.

the hdc will turn off when the brakes get too hot so always be ready to use your foot on the brake

scarecrow243 said:

the hdc will turn off when the brakes get too hot so always be ready to use your foot on the brake

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This^^^^ Although the HDC ECU doesn't actually know how hot the brakes are. It likely uses a time, speed, applications algorithm to determine brake temperature.
The system fades out much earlier than necessary Imho.

Skinny Mike said:

The hdc will not go over 5 mph that's why the brakes engaged and made noises.
It also works great uphill if on ice/snow. And on levelish ground if in deep mud or on a pebble beach etc. In fact if you get stuck just switch it on and engage first, it's never failed to pull me out of what I'm stuck in yet.
Cheers
Mike

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Saying HDC won't go over a speed of 5mph isn't exactly true. The HDC sets a target speed of 5mph off the throttle. You can use the throttle to set your own target speed if you prefer.
TC is what gets you up a snowy hill. It's automatic in operation

Ok make myself clear,
mines an auto, put it in first select HDC and it goes virtually anywhere
https://www.dropbox.com/s/mw9y6xdptxzn5jx/2010-12-01 09.12.55.jpg
The pics from 2009 when most of Sheffiled came to a stand still, I got to work when all roads were shut and the only thing on the roads were 4x4's. To get to work I have to go up some serioulsy steep hills, got to one (Manor lane past Manor castle) and it would not go up so 4th attempt went back down 10 foot selected HDC and it went staight up, tried it on a few other occasions in mud on beaches etc and it always works better, as i said though mines auto so its a bit different.
Mike

The hdc, traction control, and abs are all linked.

The TC works all the time and hdc only works to control your speed in a down hill situations hen it is switched on.

The traction control gives you the ability to go up hills with limited grip. You only need one wheel to have grip to make progress. Manual or auto the systems work the same.