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VX9 low range auto issues

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Matthew Stevenns

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Discussion starter · #1 ·
Hi Guys,


I had the car in low 4 this weekend on a hill decline hoping the car would give me a controlled decline. To my surprise the car changed gears and accelerated. I've called Nissan and they say its normal and pretty much fobbed me off. Anyone had similar issues and any way to fix. I know Nissan asia site has had some chat but no results.


TIA
 
#6 ·
so held in 1?

It should not change up unless your speed exceeds the box safe parameters which in low is unlikely unless you accelerate past it, the software will then change up, in my experience all auto boxes with an ECU do the same old school mechanical boxes wont
 
#7 ·
cssuk said:
so held in 1?

It should not change up unless your speed exceeds the box safe parameters which in low is unlikely unless you accelerate past it, the software will then change up, in my experience all auto boxes with an ECU do the same old school mechanical boxes wont
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Agreed, but in mine if you select low range and lock it in first it will never change up, even revving to the red line at 5,000 rpm it stays in first. Thats what you want from an off-roader - to keep it in 1st low on steep descents.
 
#8 ·
yes it should but its not clear if the stick was in 1 or d with 4 low in the transfer case, i do know most modern auto box ecus will override the controls if condtions demand it and the box will end up outside its operating parameters whether the meat sack inside it likes it or not, my old patrol would actually lock the wheels if held in 4 low and 1 rather than change up but my Jeep which was electronically controlled 6 speed would change cogs if pushed too hard
 
Discussion starter · #9 ·
Sorry for the confusion guys. The car has a semi auto gear box with a manual mode. I was in manual mode and locked it into 1st. I've done this in the past and I believe it has held. I took the car in about 4 months ago for warranty issues, leaking intercooler, and they did a software update. I hadn't tested the slow decline till last weekend as I hadn't had opportunity. Last weekend I commenced the hill decline and after 2.5k revs the gear shifted to second. I had to apply breaks and manually bump it into 1st again. same things happened again so I had to keep the speed down by riding the breaks.
As stated, I called Nissan and they said " we've had a few phone calls with people concerned with this, and it's how the car is meant to perform" I'd already explained that once it hadn't done it and asked if anything could be done, they say " no nothing can be done as its how the car is meant to perform" so i'm not too pleased.
 
#12 ·
Surely better than a wrecked engine?

I notice that some hill-descent systems, which is what you probably need, apply the brakes automatically to maintain a certain speed. If this were not the case, there would always be a hill out there steep enough to over-rev the engine. An exhaust brake might help, but I don't know of any pickup that uses one. A petrol engine is better for engine braking, on account of it having a throttle, unlike diesels....
 
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#13 ·
freemansteve said:
Surely better than a wrecked engine?



I notice that some hill-descent systems, which is what you probably need, apply the brakes automatically to maintain a certain speed. If this were not the case, there would always be a hill out there steep enough to over-rev the engine. An exhaust brake might help, but I don't know of any pickup that uses one. A petrol engine is better for engine braking, on account of it having a throttle, unlike diesels....
Click to expand...

A good off roader will hold a gear in low range even if it throws mechanical parts through the bonnet. The alternative in some terrain is to fall out of control off the side of a cliff.

That being said, some autos, especially Toyota, will change up regardless. This is why old school off road drivers prefer manual Toyotas (to the extent that an auto gearbox is not offered on the 75, 76 or 79 series Land Cruiser).

Whether the gearbox will change by itself or not depends on company philosophy. I'll admit I cannot speak to older models, but while the NP300 is (often infuriatingly) reluctant to change up or down manually in low range, once it has done so, it will hold low range first with the rev limiter pinging, all day.
 
#14 ·
If a hill descent becomes long and steep enough, any engine can get over-revved irrespective of using a manual gearbox or rev-limiters - these will help but only up to a point. This happens on-road too, particularly with 4.3t of trailer, I have found, and early cadence braking is what you have to do in that example.

Seems to me that a Nav is a dual-purpose, low-cost work and leisure vehicle. It is not designed or optimised to be an extreme off roader - if it were, there would be no need for many of the mods I see on the forum. And that 'jack of all trades, master of none' feel suits the vast majority of buyers, I would think..
 
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#16 ·
Landmannnn, if the gearbox in yours does not change up in low-range, then assuming the hardware is the same as the OPs, and all the reported facts are correct, it must come down to different revisions of software. So, to your point, I doubt there is a resolution, but only because I very much doubt the OP will be able to find a tech who has the knowledge to compare or test different code packages.
 
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#19 · (Edited)
Surely it's saying torque converters essentially free-wheel when off the throttle, but this 'coast control' mimics what a manual box (ie it lets the wheels drive the engine to provide engine braking).

I have been down some steep (road) hills when towing, and selecting sport helps, as it changes down earlier to give you more engine braking. When any hill is steep enough however, the momentum of the rig will start to race the engine. It is a good thing that the box changes up so as not to wreck the engine, but in the end you have to brake to reduce speed, else you run away. The point being that all automatic hill-descent controls use the brakes to control speed because engine braking alone won't slow you down on steeper hills (or indeed not very steep hills at all if you are heavy enough) as I mentioned before.

To my knowledge, no Navara or similar pickup in Europe has "exhaust braking" this is a different idea, nothing to do with descent control or "engine braking". It's effective, fitted to many big trucks, and a few big US pickups to aid braking or as a last resort if brakes fade.
 
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freemansteve
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