4L vs 4H

[Gbt]

I was wondering about any potential problem of driving in 4L. Some of the tracks I drive often have short rocky climbs where I use 2nd in 4L to climb up, then the track straightens out where the speed gets up to ~30km/hr, then I have another short rocky climb in 2nd in 4L.

What I would like to know, is it "best paractice" to stop after the climb and change back into 4H for the drive to the next rock section? or, Is it fine to drive around in 4L but use 5th and/or 6th gear on the straight flat sections for extended periods of driving? Pros and cons please...

Also, when I am driving in 4L I usually have my window down, and sometimes when I change gear I hear a mechanical clunk (sounds like the gears engaging). Is this a normal noise and I only hear it because I am going slow with the window down, or is the clunck and indicator of some slack some where in the drivetrain?

 

[bradm84]

Should be fine as far as I have heard to use 4L whenever on dirt only, even on flat ground.
When I go 4x4ing in 4wd parks I put it in 4L when I leave the campsite and leave it there all day until I get back to the campsite.
When I'm out in a state forest though, I have it in 4L when on any decent tracks and only go to 4H when I am travelling a distance between tracks and the speed is higher. I generally won't go over 60km/h in 4L.

That's what I have done in all my 4wd's including the Navara and haven't had any issues.
Not sure if anyone else does it different. If I've been doing it wrong I'd like to hear it as well.

 

[bradm84]

The other exception is Beach work, where I use 4H almost always and have only gone to 4L a handful of times in some really boggy sand.

 

[Gbt]

I am pretty much in the same boat. 4H for sand, except when I am crawling out of something. I was just concerned about ticking along in 6th in 4L and if it stresses anything out...

 

[bods]

I'm not sure on the d40s, but from memory in the d22s they have a thing on the back of the driver's side sun visor that you shouldn't go over 45km/h in 4L. I can't see a problem with not changing out of low for a short distance and I'd say you're on the right track with the clunk being driveline backlash, especially when in 4wd as everything is being driven, the front end isn't free wheeling like it is in 2wd.

 

[Jased22]

Yeah stay in low range. No need to change. But i always thought it wasnt good to use 5th gear in low

 

[Old.Tony]

From a mechanical viewpoint, 4LO just employs a reduction gear. Nothing is happening in the vehicle in 4LO that can't happen in 4HI - it's the ratios that change.

The big deal about vehicle speed is the rotational speed of the input side of the transfer case. The output shaft of the transfer case is fine, it does that sort of thing all the time, but the input shaft is rotating something like 2.6 times faster than normal. At 100km/h it'd be like running the gearbox output shaft (in 4HI) at 230km/h. I doubt the drive train is designed for that.

However, if you're happy to limit yourself to 50-60km/h between the tougher sections, then stay in 4LO.

 

[Gbt]

Excellent, on the tracks I frequent 40km/hr is fast. All good, no dramas. Cheers.

 

[Old.Tony]

Just another point to ease your minds: the Navara isn't capable of 230km/h. There's a governor that restricts the engine to 5000 RPM. Top speed is about 90km/h (YD25 power plant, 3.692 diff ratio, 2.625 transfer ratio, top gear, 5000rpm, 255/70R16 tyres will do 89.758km/h in 4LO before the ECU cuts the fuel off).

Your car is more than capable of this speed on either end (input or output of the gearbox/transfer case).

The biggest issue for me at those speeds is the phenomenal amount of torque available. One wrong move - one twitch of the steering on ground that's a little too firm - you could create history (Guiness: fastest non-deliberate destruction of a 4WD transfer case/chain/CV/axle/diff/uni/etc).

But if you are taking it easy, not pressuring the steering too much, there's no reason why you can't do 60km/h in 4LO.

Warning: KCs have a funny issue in 4LO in 4th gear. Their fuel rail starts spiking the rail pressure, it's almost like an odd heartbeat graph. You'll experience it as a surging. Put it in 5th and it's supposed to go away. Back to 3rd gear and all is good, but in 4th the stupid thing surges. Go figure - it'll be some software thing, maybe a reminder that you shouldn't be fanging it with that much of a torque multiplier under you!