NPS fines AWD owners…

[DaveInDenver]

They increase the gearing range a little, but it's more for MPG than anything else. By comparison, the transfer case on my truck is a 2.64:1 ratio.

Comparing a F150 10spd 3.73 to my Tundra, the overall gearing is:

F150: 1st = 17.5
Tundra: 1st = 14.3, 1st Lo = 37.8

So 1st on the F150 is still over twice as high.

You answered exactly the question I had. Thanks! I want to say that I can't imagine how they'd get away with no low range but I know why it can be.

I used to wonder why they stopped putting locking hubs on trucks, what with the potential increase in MPG you'd get removing that drag. Oh, yeah, there's probably some marketing angle about a night on the town and getting your tuxedo soiled.

But I came to the conclusion that perhaps the more likely reason is if they didn't spin the diff ring gear with one side the condensation and lack of lube would be a warranty nightmare from the seized and rusted gears inside. 4WD truck owners used to know to lock them in periodically, or just actually used them enough...

 

[IdaSHO]

When I see legislative changes like these I look at them as final efforts to keep dumb people from doing dumb things. Unfortunately, the next step could easily be partial or complete closure of problem areas. Regardless of how things ate defined or how informed LEOs are, its always easier and cheaper to lock a gate than the police the dumb people.

 

[plainjaneFJC]

When I see legislative changes like these I look at them as final efforts to keep dumb people from doing dumb things. Unfortunately, the next step could easily be partial or complete closure of problem areas. Regardless of how things ate defined or how informed LEOs are, its always easier and cheaper to lock a gate than the police the dumb people.

If laws were really focused on dumb people that do dumb things then they’d be passing laws against themselves…

 

[1stDeuce]

They increase the gearing range a little, but it's more for MPG than anything else. By comparison, the transfer case on my truck is a 2.64:1 ratio.

Comparing a F150 10spd 3.73 to my Tundra, the overall gearing is:

F150: 1st = 17.5
Tundra: 1st = 14.3, 1st Lo = 37.8

So 1st on the F150 is still over twice as high.

This is correct, but do you really need such low gearing in normal use? I suspect the answer is that 17:1 is plenty low for most use.

Look at it this way... In the 70's, a Chevy with a TH400 and a 203 or 205 transfer case had a lowest ratio, assuming 3.73 gears, of 18.6:1. That's barely lower than the new F150 that you pointed out. Coupled with the transmission option on new trucks being an auto, I suspect they're plenty low for 99% of intended use, even without low range.

All I'm saying is that low range might not really be a deal breaker for this, even though the NPS points it out as "necessary". In practice, it's going to be pretty hard to know if a newer half ton truck has it or not.

Just food for thought...

 

[rruff]

In practice, it's going to be pretty hard to know if a newer half ton truck has it or not.

And... the assumption from the article that 4wd will have lockers, is not correct either.

 

[1stDeuce]

And... the assumption from the article that 4wd will have lockers, is not correct either.

Nothing in the compendium or the letter to subaru owner that suggests the NPS thinks about lockers. Only mention of that is speculation in the article written by Jalopnik... I read everything they write while keeping in mind that most of them are enthusiasts, but also generally pretty clueless about what they're writing about from a technical perspective... It's mostly entertainment with sometimes a tiny bit of enlightenment...

 

[tirod3]

A lot of modetn 4WD still lock and unlock the hubs. Fords use vacuum to engage the hub splines, one hack is to control each thru a manual control when needed. Differentials are a mixed bag, a limited slip geting hammered thru a corner locks up, a ratchet at lower speed or with better grip - tires have some influence - won't disturb as much. There's no guarantees out on the trail.

Having owned both a 90 Cherokee and 99 Forester, I was at one time comparing them side by side in the drive and on dirt. That Jeep was no match for the Subaru. Neither had lockers, the Forester was AWD, vs 4WD, and losing traction was beyond my willingness to explore. The Jeep, tho, got me towed in my own yard. By my son's. He was on more level, dry ground.

Both had the same ground clearance, about 8", Jeep to the bottom of the differentials, Subaru to the unibody. The unfortunate situation with law, tho, is when too much is specified yet progress goes on, negating the letter and even mocking it.There is also the matter of skill, rarely taken into account.

That is where "officer discretion" comes into play. Just because someone owns a highly capable vehicle, it's no indicator of skill. Surf "Lambo crashes" for examples, altho many would dispute it. Nonetheless, a good driver with a less capable vehicle can negotiate terrain that a poor driver would fail in a great off road vehicle. The issue is the patrolling officers see it all the time, and they make the call, not our ego.

 

[DaveInDenver]

This is correct, but do you really need such low gearing in normal use? I suspect the answer is that 17:1 is plenty low for most use.

Look at it this way... In the 70's, a Chevy with a TH400 and a 203 or 205 transfer case had a lowest ratio, assuming 3.73 gears, of 18.6:1. That's barely lower than the new F150 that you pointed out. Coupled with the transmission option on new trucks being an auto, I suspect they're plenty low for 99% of intended use, even without low range.

That is an interesting observation about TH400 (2.48 1st) + NP205 (1.96 low) + 3.73 axle gears. It would have been driven by a small block but an emissions neutered V8 back then would not have much power anyway. So a modern even turbo I4, nevermind the V6 or V8 options, with a 17:1 is probably as good or better.

So yeah, in the context of driving a mildly difficult NPS road having half again or more lower crawl probably isn't strictly necessary. I think having a part time transfer or a locking center diff is an important feature in technical situations. Even with a low or lower crawl the full time Toyotas I'm familiar with can overheat the center diff and I would imagine in an AWD this could be a significant issue. Also the traction control and being able to disable it, which is AFAIK all trucks do in low range.

Guess the point is a car that can do well in snow and even has some clearance does not make it an "off road" (off highway!) capable vehicle for extended use. Even these new trucks without low range aren't intended for it, the use case being more to keep them from being stuck on a muddy construction site more than get you around 100 miles of 4WD road. That's the thing with that old TH400/NP205, it's could take a lot of abuse. I mean, though, I don't know what the drivetrain in this example new truck looks like. So maybe it's alright in this respect.

 

[Jupiter58]

My experience with my wrangler rubicon and f150 on difficult terrain was I used 4 lo mostly for long steep slippery descents (like in the rain) where consequences were not something you wanted to dwell on. Definitely kept the braking to a minimum. Sometimes on climbs which were very steep and rough or having to restart mid climb. Situations I would have been uncomfortable with in my outback.

 

[deserteagle56]

Transfer case in Lo range makes it much easier on the automatic transmission when in difficult terrain. I always use low range when climbing steep roads at low speeds (and back down those same grades also). Matt of Matt's Off-Road Recovery makes that point in one of his latest videos. He has temperature gauges on the trannies in his recovery vehicles and sees a big difference - much lower - transmission temperatures when using Lo range versus Hi range.

 

[casioqv]

DEFINITION

A four wheel drive vehicle is defined as a sport utility vehicle (SUV) or truck with at least 15-inch tire rims and at least eight inches of clearance from the lowest point of the frame, body, suspension, or differential to the ground. Four wheel drive vehicles have a transfer case between the front and rear axles that locks the front and rear drive shafts together when four wheel drive is engaged. All wheel drive (AWD) vehicles do not meet this definition.

Interesting... by this strict definition a lot of light duty cars nobody think of a 4x4s would count as four wheel drive here, and a lot of purpose built 4x4s would not! My wife's Nissan Rogue checks all of the boxes just barely: 8.2 inches ground clearance, a button that locks the center diff below 18mph, and 17" wheels. Nissan calls this AWD, they do not call it four wheel drive. I think a lot of small japanese vehicles without low range have some type of center diff lock, and meet all of these criteria- I know the first gen Toyota Rav 4 has a locking center diff.

I think one could even find some small sports cars that meet all of this criteria... the 80s/early 90s Subaru XT could even be ordered with air suspension, a center diff lock, and 15" wheels, however I think most only had 13" wheels.

Plus you'll find some pretty serious purpose built offroad vehicles that technically don't meet this- For example you can buy a Porsche Cayenne 958 with rock sliders, air suspension, rear diff lock, swaybar disconnects, etc. but with a Torsen style center diff that doesn't qualify. Quite a few members on here do some really impressive technical stuff in these vehicles.

I'd also bet if you take their definition completely literally, most purpose built 4x4 trucks with solid axles and/or leaf springs don't truly have 8" of clearance from the lowest point of the differential, or bottom of the suspension parts on the stock tire sizes. I'm pretty sure a Jeep CJ-7 for example really only has about 7" of clearance by this standard... interesting that this would make a stock japanese sports car count as a 4x4, but a stock Jeep may not qualify. A lifted pre-runner with a rear locker certainly would not. I've seen really aggressively built Jeeps that drop to small wheels for massive sidewall when airing down- not a four wheel drive anymore in that case?

I'd change it to something more like this:
Vehicles must be equipped with all terrain tires, have adequate ground clearance to avoid body/suspension contact on the road being driven, and drivers must have adequate skills levels and carry proper equipment for the conditions. The drivetrain must be capable of providing motor torque to at least 2 wheels at all times, even if all other wheels have no traction.

 

[sg1]

Interesting. I have two Ford Transit AWD campers, one in Europe and one in Canada. Both have 16 inch rims and enough ground clearance to meet the requirements. The European Transit has lockable push button 4 wheel drive, the Canadian one a system where a computer decides how much power goes to which axle. In reality the Canadian Transit is more capable because it has a lot more low end torque and an automatic transmission.