Steep downhill control of an RB30 Patrol

I have read how to descend steep hills in a diesel powered vehicle: 1st low range and do not touch the brakes.

After only having done a few easy drives on hilly / muddy tracks, I wish to learn how to tackle difficult terrain in an RB30 petrol powered Patrol.

Compared to the gearing used for a TB42, 1st gear behind the RB30 is very tall and engine braking is minimal, even in low range.

I have tried to descend some very steep, but short tracks locally, by using different methods.

Using just the engine, it revs to about 2500-3000 RPM before there is any noticeable braking effect.

Of course, by that time the speed is suicidal and I have had to apply the brakes so as not to smash into the bottom of the hill or bounce off the track.

I have also found that applying the hand brake when moving, even very slowly is not an option as it tries to grab and shudder violently.

Fix the handbrake, Cobber... much, much safer and more control than wheel braking

Apart from the grabbing issue it works quite well, there is plenty of meat on the shoes and is within the specified limits, so what do you suggest is wrong with it?

Drum out of round/needs machining?

I will have to check that somehow.

Mudnut,

Even in a Diesel, we have to dab the brakes every now and then to keep speeds under control ..... depending on the grade of the slope. My diesel will sometimes run out to 3000 rpm if I don't.

You may just have to do it a little more often.

I have never driven an RB30, but it must have some engine braking .... I just suspect that it would be at it's best around 4000 rpm which would make it just a little more disconcerting.

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Originally Posted by happygu

Mudnut,

Even in a Diesel, we have to dab the brakes every now and then to keep speeds under control ..... depending on the grade of the slope. My diesel will sometimes run out to 3000 rpm if I don't.

You may just have to do it a little more often.

I have never driven an RB30, but it must have some engine braking .... I just suspect that it would be at it's best around 4000 rpm which would make it just a little more disconcerting.

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Considering how tall 1st is, it is bloody frightening!

you can get different gear ratio's for the low range transfer gearbox . its pricey though . probably more than 2 grand .

Not really an option due to cost.

Hey Mudnut,

As you know I have an RB30 too. I have done quite a few steep hills, including some... interesting... wheel lifts (front and rear) in my rig. The below is just my experience with my rig. Handbrake issue first, I have applied it before and it did aid my braking somewhat with no shudder, so perhaps there is something to look at with yours? Contaminated surfaces perhaps?

As for engine braking, yep nothing like a diesel it but has reasonable engine braking. It's still faster than I'd like to be going sometimes, but I guess I have gotten used to it. I know what you mean with just how tall low first is, if you haven't driven one I don't think you can comprehend just how fast it will go in that gear.

At least in my experience with my GQ I have found that as I tip into a steep descent, even in low 1st it has a tendency to run on and the first couple of times I fairly shat as I thought it would run away, but once revs hit about 4000 (as happygu says above), it does pull it back into line a lot. Once I got used to it, I got relatively comfortable with some pretty steep hills. Mine at least doesn't seem to go above 4000/4500 or so, seems to mostly hold around there, sounds strange descending with that many revs but works. I will say that I tested several RB30 GQ's when I was shopping for mine, and some felt like they had less compression on road when gearing down, perhaps due to more engine wear? Maybe with one of those my experiences would have been different.

I did a lot of dry hills first and am still always careful on muddy ones. Depending on the hill and conditions I will sometimes use the brakes, particularly if there are steep entry drops or rock steps as it will not pull me up enough to avoid smashing the long range tank as it drops off (I have a dent in the tank to remind me)...

Overall mate, I think it will be a matter of what you are comfortable with in your vehicle. Always better to avoid injury or unnecessary damage I reckon.

Cant help too much muddy as i don't have an RB30 but my advice is to always take the chicken track if it's an option. I've done some gnarly tracks up and down but if presented with an option, generally take the chicken track (some exceptions when the blood's boiling). Never be pressured by the group (and good groups would never pressure you). Always better to enjoy the beer at the end of the day than to go all out to keep up with those who inevitably smash their rigs.

Then again you may be asking because you want to or have to and in that case I can't offer you any RB30 advice.

Hey mate, as you know I've got rb30 and steep downhills on 35's was white knuckle stuff. Still sucks on 33's.

Couple of things I learned - find a steep but grippy down hill, something safe, so you can get comfortable with the speed. Plenty a muddy downhill I've done where I've just let the car gain speed and focused on keeping her straight. Of course, not always an option if there's a sharp bend at the bottom, but sometimes it's handy knowing how to do.

Other times, I just make sure I start really slow, and just inch it down. I tend to work the brakes on and off, to try and keep the wheel spinning hoping to avoid a slide. If it's really gnarly, sometimes I'll have the car in reverse with clutch in, so if she does start to go and i can't stop her, I just drop the hammer until she stops (have it in first if you are backing down a steep incline).

Honestly, a lot of it's situational. First low is just too tall in these boxes, and the motors like to rev, so its not a favourable scenario for engine braking downhill.

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Originally Posted by Throbbinhood

snip...

Other times, I just make sure I start really slow, and just inch it down. I tend to work the brakes on and off, to try and keep the wheel spinning hoping to avoid a slide.

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If you mean what I think then that technique is known as 'cadence braking', very common in colder climes where ice etc is an issue, Europe, Canada, US.
Can be quite effective with experience but must admit I have never came close to mastering it
I think it is still taught in the ADF but not sure.

Quote:

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Originally Posted by Throbbinhood

snip...

If it's really gnarly, sometimes I'll have the car in reverse with clutch in, so if she does start to go and i can't stop her, I just drop the hammer until she stops (have it in first if you are backing down a steep incline).

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Jeez dude... that is more than just a tad dangerous thing to be doing IMHO.
An old school 4WD saying is "your right foot may get you there if your left foot doesn't kill you first" meaning you should NEVER be 'clutch in' on a steep ascent/descent

Why wouldn't you attempt the challenge in the correct gear and just turn the ignition off if the speed gets too high and then do a stall recovery technique?
Even if you did it multiple times you would get to the bottom of the challenge without having ever lost control of the vehicle or shitting yourself.

In my Petrol 'Cruisers and MQ Patrol days thats what we would do and indeed is still a basic technique in both Diesel or Petrol vehicles on 4WD courses.

As an experiment, I did shut the ignition off in my old Corolla a couple of times when doing some really steep descents, as it was Fuel injected. I found that the vaccuum created by the engine was sufficient to operate the brakes. The engine brake effect was great but the problem with doing this with the RB30 is that it will suck the carby dry and probably blow the exhaust system and air filter into space when the ignition is turned back on.

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Originally Posted by the evil twin

Jeez dude... that is more than just a tad dangerous thing to be doing IMHO.
An old school 4WD saying is "your right foot may get you there if your left foot doesn't kill you first" meaning you should NEVER be 'clutch in' on a steep ascent/descent

Why wouldn't you attempt the challenge in the correct gear and just turn the ignition off if the speed gets too high and then do a stall recovery technique?
Even if you did it multiple times you would get to the bottom of the challenge without having ever lost control of the vehicle or shitting yourself.

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I do that too, but it doesn't suit every situation. I'd rather have power available, power steering and vacuum assisted braking - than no steering, no assisted brakes, and ability to power out/reverse, no choices basically.

"Why wouldn't you attempt the challenge in the correct gear and just turn the ignition off if the speed gets too high and then do a stall recovery technique?"

I've done both techniques plenty, they both have their place. My gearing is too long to have the clutch out and have it in gear (even low first) at really slow speeds down a hill. Once my tyres are clogged up, they aren't going to clear with the engine off slipping and sliding down a hill. Some steep slippery clay hills, i'll be picking up speed with all four wheels locked and engine off. I've tried it. No technique is a be all and end all.

Quote:

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Originally Posted by the evil twin

If you mean what I think then that technique is known as 'cadence braking', very common in colder climes where ice etc is an issue, Europe, Canada, US.
Can be quite effective with experience but must admit I have never came close to mastering it
I think it is still taught in the ADF but not sure.




Jeez dude... that is more than just a tad dangerous thing to be doing IMHO.
An old school 4WD saying is "your right foot may get you there if your left foot doesn't kill you first" meaning you should NEVER be 'clutch in' on a steep ascent/descent

Why wouldn't you attempt the challenge in the correct gear and just turn the ignition off if the speed gets too high and then do a stall recovery technique?
Even if you did it multiple times you would get to the bottom of the challenge without having ever lost control of the vehicle or shitting yourself.

In my Petrol 'Cruisers and MQ Patrol days thats what we would do and indeed is still a basic technique in both Diesel or Petrol vehicles on 4WD courses.

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Clutch should never be disengaged on descents, simply asking for trouble. Agee 100% with what ET says above. When I had my 2.8td engine, same problem as Muddy has, so I dropped in a set of marks 85% gears and fixed it, but this is not an option, so just feather the brakes and start slow.

I had a bit of an insight as to what might happen on a trip to the Otways, with the tyres I am running. I had these brand new BFG Rugged Terrains and after a light shower, they struggled a bit on a steep ascent.

I will definitely go for a chunkier tread next, even though I do 99.99% on road.

Would have to agree with ET and PeeBee, would never have the clutch disengaged on steep descents and 4wd training I have had has taught the same. Any engine braking is going to assist and occasional light application of brake to keep the speed down or as others have said, fix your handbrake and use that.

Quote:

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Originally Posted by mudnut

I had a bit of an insight as to what might happen on a trip to the Otways, with the tyres I am running. I had these brand new BFG Rugged Terrains and after a light shower, they struggled a bit on a steep ascent.

I will definitely go for a chunkier tread next, even though I do 99.99% on road.

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Your trip to the Otways, was that the day trip in 2014? It get bloody slippery when it rained but I felt ok with my BFG AT's.

Yup. My Q's bum was all over the shop.

Hey mudnut. Did GQ wirh RB30s have a different gearbox ratio???
I used to owne a GQ with a RB30 and up the high country decending in 1st LOW i had to tap the accelerator a lot and not the brake. I'm wondering was this due to different gearing in GU's that youre experiencing. Ironically it was the gearbox letting go on me in toolangi that ended the GQ...

I am not rapt with the lighter gearbox bolted to the RB30. Yes they had a higher first gear, as its guts is designed for skylines. When I was seeking info about rebuilding the first gearbox that let go, a supplier confirmed that it had the same ratios that Commodores ran.

Quote:

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Originally Posted by mudnut

I have read how to descend steep hills in a diesel powered vehicle: 1st low range and do not touch the brakes.

After only having done a few easy drives on hilly / muddy tracks, I wish to learn how to tackle difficult terrain in an RB30 petrol powered Patrol.

Compared to the gearing used for a TB42, 1st gear behind the RB30 is very tall and engine braking is minimal, even in low range.

I have tried to descend some very steep, but short tracks locally, by using different methods.

Using just the engine, it revs to about 2500-3000 RPM before there is any noticeable braking effect.

Of course, by that time the speed is suicidal and I have had to apply the brakes so as not to smash into the bottom of the hill or bounce off the track.

I have also found that applying the hand brake when moving, even very slowly is not an option as it tries to grab and shudder violently.

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I guess there's an issue with the hand brake shoes/drum to give out a shudder like that.

I've done steep downhill engine braking on first gear, but can't remember I compensated with brake or not.
I'll have to try again.