Steep, rocky climbs - throttle control and gear selection

[insect_eater]

I did the first two days of a three-day 4wd course on the weekend, and need some advice on tackling steep, rocky climbs.

Firstly, I have a NX manual with 14Kkm, with fresh 50mm lift HD springs. The tyres are Dueler 697s (265/65, 70% tread) at 20 psi. Although I have a TJM steel bar, winch and LR tank, it is oversprung when unladen.

Many of the climbs were tight through trees and rocky - shaley, but grippy (when the wheels were on the ground....).

I found that I struggled to hold the recommended 2nd gear (LR). If I went as slow as asked, or necessary to wind between trees, the revs dropped to below 1500, when the throttle became unresponsive. When this happened, it either:

1. stalled
2. the revs flared (5-700rpm) when it lifted a wheel, and if I caught it cleanly, it would proceed up,
3. it chugged up without my ability to increase revs (EDIT heart in throat, waiting for stall)

In all of these circumstances I didn't feel in control of the vehicle - I couldn't feel how much throttle had been dialled in (the throttle was unresponsive), and whether it dies or proceeded was a function of the terrain and my ability to moderate flaring revs in a way that avoided losing turbo spool but minimising wheelspin (TC seemed a little slow....).

I could easily drive up these slopes in first, but was advised that this was too dangerous as 1st had too much torque, and there was too much risk of breaking traction.

I am obviously inexperienced, and do need to learn better throttle control, but I am reasonable mechanically attuned and sensitive to engine load/control.

Any thoughts appreciated

[andy_q]

Pajero's do not have a very low range so depending on the instructor this may not have been taken into account. It sounds to me like first is probably the correct gear.


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[Aussie_Dan]

I could easily drive up these slopes in first, but was advised that this was too dangerous as 1st had too much torque, and there was too much risk of breaking traction.

The torque that the engine produces, and hence the torque sent to the wheels, is directly proportional to how heavy your right boot is.
If it were me in the situation you have described, I would be using first gear. Just go easy on the throttle....
Cheers, Dan.

[NJV6]

I have a NT manual and what you experienced is my biggest dislike of this vehicle. You would be better off in 1st, remember most other vehicles have a much lower 1st gear so therefore a lower 2nd gear as well. 1500rpm is often far to fast in 2nd so you do need to use low.

I just use low in those circumstances, its far easier on you and the vehicle, the dead spot down low is pretty poor on these, my other shorty (V6) is far easier and more forgiving to drive slowly than the 3.2 as low down performance is far superior.

I also discovered the engine got warmer on the ultragauge (up to about 104) when climbing in 2nd (struggling) and intake temperatures were over 100 as well. Once I started using 1st and had a bit of boost on board everything dropped including my temperature as it was pretty high to do disappointment in the engine. My 2.8 hilux will eat the pajero until 1500-1700 rpm.

[Aussie_Dan]

I have a NT manual and what you experienced is my biggest dislike of this vehicle. You would be better off in 1st, remember most other vehicles have a much lower 1st gear so therefore a lower 2nd gear as well. 1500rpm is often far to fast in 2nd so you do need to use low.

This is one downside to the NT onwards (with manual trans). They use a 3.9:1 diff ratio from memory.
I am not sure what the NS manual uses.
The NM / NP 3.2 manuals use a shorter 4.1:1 diff ratio. Whilst they might rev a little higher on the highway, they pull better from low RPM like in the situations we are discussing....
Dan.

[BruceandBobbi]

Was the course at Braidwood?

You know the talk. If it isn't a Toyota or Nissan it isn't a real 4X4.

We use 1st if the terrain warrants it.

[nj swb]

As long as there's somebody else around when you're driving your 4by, you'll have somebody giving you advice. Not all of it will be good, which is something you learned on your course that wasn't necessarily on the curriculum.

As noted by others, Pajeros have a relatively poor low range, so our low range 2nd is rarely as low as low range 2nd in most other 4wds. Most of the time, low range 1st will be a more appropriate choice.

Generally, if in doubt, select a lower gear.

About the only time I question this is on steep & loose climbs, for two reasons:
1. If the terrain is too loose, a lower gear is more likely to spin.
2. If the terrain is steep & the loose is patchy, you may need momentum to carry you over the loose spots - low range 1st may be too slow to develop the momentum you need.

At the end of the day, I'd rather not make a climb because I was going too slow. Going too fast is more likely to lead to trouble, so if you're not sure, try slow first.

[insect_eater]

Thanks andy_q, Aussie_Dan, NJV6, and BruceandBobbi

First did just make sense to me, but not to them...

When below boost and gravity was exceeding torque, right foot did nothing (except lose my sense of throttle position, and risk of flare when traction lost). When in first, I had that direct relationship between throttle and torque - so that felt like the right gear, as you suggest

I didn't look at the ultragauge -but my feeling was that I was operating the engine outside it's comfort zone, so I' wouldn't be surprised if it was starting to raise temps.

I did wonder about diff ratios - sounds like the earlier gens had better crawl capacity.

The course wasn't at Braidwood, but 'real 4WD's' and '80 or 70 series/patrols' seemed a constant focus.

[insect_eater]

NJ swb - thank you for your counsel (especially the thought about the extra-curricular topic)

The hard part for me is discerning between good and bad advice - I'm trying to balance the feedback from the vehicle (again trying to work out whether it it my inexperience or unfamiliarity of the vehicle, or inherent vehicle limitations) against the advice who have much more experience than I about what a 4WD should be able to do.

[nj swb]

NJ swb - thank you for your counsel.

The hard part for me is discerning between good and bad advice - I'm trying to balance the feedback from the vehicle (again trying to work out whether it it my inexperience or unfamiliarity of the vehicle, or inherent vehicle limitations) against the advice who have much more experience than I about what a 4WD should be able to do.

That is always the trick - knowing when to trust others, and when to trust your instincts. It all comes down to experience - obtaining your own, so that you can better evaluate the experience of others.

You're obtaining experience.

[old Jack]

Unless the Instructor is familiar with the Pajero and other medium size modern 4wds (and most are not) then they will have little or no idea about how to get the best out of a modern 4wd, and teach to the National Standard which is out of date in so many areas and does not suit many modern 4wds. This is one reason why I refuse to be an accredited trainer because I will not teach to the National Standard.

The NT Pajero manual trans has a low range 2nd gear low range is 17.7:1and this is not very low, combine this with a modern 4 cylinder turbo diesel that has no or little boost under 1800rpm and you have a vehicle that will struggle to be able to do a controlled steep climb at low speed over broken ground. 2nd low is only marginally lower than 1st high which is 16.6:1 ratio.

However low range 1st is 31.5:1 and this is significantly lower and is a similar ratio as many "proper 4wd" 2nd low. This is the gear you should be using as it gives you the most control and less likely to stall. In regards to "too much torque" this can be counteracted by using less right foot and when the wheels start to lose traction if you back off the right foot very slightly then traction will be regained. If you are too slow at backing off then the Pajero's excellent traction control will initially apply the brake to the spinning wheel and if continuos operation of the traction control continues then engine power will be cut.

Whilst a general 4wd course is an excellent introduction to 4wdriving it is only the start. Joining a club that is manufacturer specific or similar, and doing their training will result in a greater knowledge and understanding of your Pajero. Regular trips off road with experienced people driving similar cars will result in practical skill development, experience and confidence.

Even within the Mitsubishi range you need to drive the Pajero differently to the Challenger and or the Triton, manual trans require a different technique than auto trans, 1985 differently to 2000 differently to 2016, diesel different to petrol, turbo differently to non-turbo , so there is no "one size fits all" technique that must be followed.

OJ.

[insect_eater]

Thanks OJ.

What you say about the standard is interesting. At times I felt like the course should've been named "80 series Landruiser training", as there was a resistance to tailoring the techniques to each vehicle.

Second gear felt wrong - too much speed, loss of throttle control as off-boost, and any backing off risked stalling. In first it was easy - enough leeway in revs to have full throttle control with no risk of excessive flaring when a wheel lifted, and the speed was suitable for tree dodging, line picking, and to avoid jolting around. I felt comfortable (although with healthy trepidation) and in control of the vehicle in first, but neither comfortable nor in control of the vehicle in second.

After 4hrs doing these climbs and descents on the first day, I suggested the above to the in-vehicle trainer, and I thought he concurred. However, the next day, at the direction of the head trainer, I was required to attempt all climbs in second (with a 5psi reduction in tyre pressure). Most I just managed, but it took intense concentration to keep some spool on the turbo (it seems to hold some spin to around 1500, as long as you haven't backed right right off and killed it), and to be ready to catch flaring revs, as many times the throttle had become unresponsive- but it often manged to chug through out of my (throttle) control.

I will pursue the opportunities to learn more and gain confidence. I think I'll also give greater credence to my feel for what is right for the Pajero.

[old Jack]

Thanks OJ.

What you say about the standard is interesting. At times I felt like the course should've been named "80 series Landruiser training", as there was a resistance to tailoring the techniques to each vehicle.

Second gear felt wrong - too much speed, loss of throttle control as off-boost, and any backing off risked stalling. In first it was easy - enough leeway in revs to have full throttle control with no risk of excessive flaring when a wheel lifted, and the speed was suitable for tree dodging, line picking, and to avoid jolting around. I felt comfortable (although with healthy trepidation) and in control of the vehicle in first, but neither comfortable nor in control of the vehicle in second.

After 4hrs doing these climbs and descents on the first day, I suggested the above to the in-vehicle trainer, and I thought he concurred. However, the next day, at the direction of the head trainer, I was required to attempt all climbs in second (with a 5psi reduction in tyre pressure). Most I just managed, but it took intense concentration to keep some spool on the turbo (it seems to hold some spin to around 1500, as long as you haven't backed right right off and killed it), and to be ready to catch flaring revs, as many times the throttle had become unresponsive- but it often manged to chug through out of my (throttle) control.

I will pursue the opportunities to learn more and gain confidence. I think I'll also give greater credence to my feel for what is right for the Pajero.

Never discount the set of the pants feelings, if it doesn't feel right then do not do it!
When I train people I teach that you must become one with the vehicle and use all your senses, sight, hearing, feel and smell.
See, what lies ahead, read the terrain.
Hear what is happening, does it sound good or bad?
Feel through your hands, feet and backside what is going on with the steering, brakes, engine, gearbox, tyres and suspension.
Smell, does the vehicle smell hot or have an abnormal smell?

Early detection of abnormal conditions, correction of driving technique and intervention can prevent damage to your vehicle.

As the saying goes "It is not what you drive but how you drive it that counts" too many people in very capable vehicles never learn to drive correctly as the vehicle covers for the drivers lack of skill and ability.

OJ.

[pajeromack]

Keep it in first, low range. The low range on the Pajero is pretty poor and makes manual 4wding very difficult on steep and stepped climbs.

Even first in 4L is still too high at times. On those extremely steep rutted climbs in my NP it would lift a wheel, traction control would brake said wheel and the car would abruptly stall. Only way up then is to slip the clutch and hope that you don't kill it.

[Axis]

This is one downside to the NT onwards (with manual trans). They use a 3.9:1 diff ratio from memory.
I am not sure what the NS manual uses.
The NM / NP 3.2 manuals use a shorter 4.1:1 diff ratio. Whilst they might rev a little higher on the highway, they pull better from low RPM like in the situations we are discussing....
Dan.

I have a feeling the NS Manual is the same ratio as the NP Manual.