4WD questions (not addressed fully before)

[jwblue]

I will start with the easy question.

 

How does the 4WD on the WD21 compare to 4WD operation in vehicles from the same era?

What about in comparison to 4WD in vehicles today?

 

Has anyone driven a 4Runner in 4WD from the same era?

 

I know this question below has been addressed in other threads, but not to the extent below.

 

This question requires careful reading.

 

 

1) When changing gears from 4H or 4L to 2H Is it necessary to disengage the hub in order to be in 2WD?

 

There seems to be an assumption that is not necessary.

 

The user's manual for the 1994 Pathfinder actually contradicts itself regarding this with the instructions

to go from 4H to 2H (and 4L to 2H).

 

On the one hand, the manual says changing from 4H to 2H can be done at any speed. This implies that it is possible

to be in 2WD without disengaging the hub.

 

Then there is a note below that statement that says.

 

For 2WD operation ..... (it then gives instructions for disengaging the hub)

 

 

 

There could be a misunderstanding.

 

When shifting from 4H or 4L to 2H, is that the same as going from 4WD to 2WD?

 

After shifting from 4H or 4L to 2H without disengaging the hub, is then driving in 2H different from 2WD? Carefully reading the instructions

above from the manual implies this.

 

 

2) Assuming shifting into 2H from 4H or 4L is shifting into 2WD, how much wear and tear is there on the transmission from not disengaging the hub?

 

 

3) I can't think of any scenario why a driver would not disengage the hub when going from 4H or 4L to 2H? Why not take the few seconds to disengage the hub?

Maybe a driver would go from 4WD terrain to 2WD terrain, then back to 4WD terrain. If so, why not just leave it in 4WD short term and not risk wear and tear on the transmission

from driving in 2WD without disengaging the hub?

Edited June 19, 2012 by jwblue

[andreus009]

I would suggest reading this thread first:

 

http://www.nissanpathfinders.net/forum/topic/6957-shifting-on-the-fly/

 

While t may not be a direct answer to your questions, it does contain the info your are seeking

[Trogdor636]

My parents had a 92 4Runner long before I owned my current Pathfinder, but I did some trails in Colorado in it. Nothing extreme, there was snow, and the 4Runner isnt bad at all. I will say the Pathfinder to me feels a little more off road capable, if that makes any sense. The 4Runner seemed better on the street, Pathfinder better in dirt. However, the aftermarket for the 4Runner is a lot more friendly, so it has that going for it. My only real dislike about the 4Runner of that generation is the V6 and its tendency to pop head gaskets.

[KovemaN]

You can shift from 2h to 4h on the fly up to 35mph. Most, if not all pathfinders came with auto locking hubs. You would need to come to a stop for the auto hubs to completely disengage, but it won't hurt anything if they are always engaged. Once the transfer case lever is shifted back to 2H the transmission is completed disconnected from the front differential so there is no chance of damage even with the hubs engaged.. Shifting from 4H to 4L requires that you be stopped with the transmission in neutral.

[jwblue]

1) When changing gears from 4H or 4L to 2H Is it necessary to disengage the hub in order to be in 2WD?

 

There seems to be an assumption that is not necessary.

 

The user's manual for the 1994 Pathfinder actually contradicts itself regarding this with the instructions

to go from 4H to 2H (and 4L to 2H).

 

On the one hand, the manual says changing from 4H to 2H can be done at any speed. This implies that it is possible

to be in 2WD without disengaging the hub.

 

Then there is a note below that statement that says.

 

 

For 2wd operation..(it then provides instructions for disengaging the hub

 

 

There could be a misunderstanding.

 

When shifting from 4H or 4L to 2H, is that the same as going from 4WD to 2WD?

 

After shifting from 4H or 4L to 2H without disengaging the hub, is then driving in 2H different from 2WD? Carefully reading the instructions

above from the manual implies this.

 

 

I believe I found the answer to the question.

 

In the owner's manual, reading further under the note with the instructions to unlock the hub.

 

This will allow for better fuel economy, quieter ride and less component wear.

 

This implies that driving in 2wd with the hub engaged can be done, but not suggested.

 

You can shift from 2h to 4h on the fly up to 35mph. Most, if not all pathfinders came with auto locking hubs. You would need to come to a stop for the auto hubs to completely disengage,

 

For clarification, isn't it necessary to drive in reverse 1 meter to completely disengage.

Edited June 19, 2012 by jwblue

[KovemaN]

For clarification, isn't it necessary to drive in reverse 1 meter to completely disengage.

 

Yes. Sorry I didn't include that.

[Tungsten]

If you want to know how it compares to other 4x4s of the same era I would say the WD21 has the best 4x4 system.

[Kyle94]

I dunno. My moms 1995 montero has an interesting setup. You can run 4hi on two settings. Both diffs locked together, or seperate (kind of like awd?) That thing has never even tried to get stuck in sand or mud... it amazes me... it has 235/75s and a bigger body so???

[Tungsten]

It's all wheel drive. They are not real lockers, just viscous couplings.

[Kyle94]

I'm not meaning locker... I mean either the transfer case spins same speed to the rear and front. Or is more like an open diff. Which was explained to me as, you can run it in 4hi on the road in rain or snow with no problems. Much like awd.

[Tungsten]

You mean a full time 4x4 system? Not sure but it might have come on WD21s and was later standard on R50s. In theory it sounds good but in practice it makes the vehicle thirstier without much of a handling advantage unless you were going really fast.

[Kyle94]

I guess? Lol. All I know is... the montero is way faster than pathy. and it doesn't try to dig in everywhere it goes lol.

But it runs at or over 3k at 70ish on the fwy where as pathy sits around 2600-2750rpm? Pathy rides nicer though. And is way more sexy! ;-)

[Tungsten]

You don't need that much power off-road anyway.

[joshellis]

It's all wheel drive. They are not real lockers, just viscous couplings.

 

Could be wrong but I'm pretty sure the Mitsi of that generation had a mechanical locking center differential much like the Range Rover Classic/Disco 1. Allows for 4x4 on any surface and Can be mechanically locked to ensure 50/50 torque split front and rear.

Edited July 20, 2012 by joshellis

[Mr.510]

How does the 4WD on the WD21 compare to 4WD operation in vehicles from the same era?

 

As far as overall layout and mechanical function it's the same basic part-time four wheel drive system used all the way back to the '20s and before. It does have automatic locking hubs, they are the only "modern" feature in the transmission of power.

 

On the one hand, the manual says changing from 4H to 2H can be done at any speed. This implies that it is possible to be in 2WD without disengaging the hub.

 

This is correct. Once the hubs are locked you can shift from 4H to 2H at any speed. You can also shift from 2H to 4H at any speed if the hubs are locked. Note that you should only shift from 2H to 4H when the front and rear tires are going the same speed. In other words, don't wait until the rear tires are spinning like mad and then yank the lever back to engage the front end. The shock loads when you do something like this are extremely high and can break almost anything in the drivetrain.

 

Assuming shifting into 2H from 4H or 4L is shifting into 2WD, how much wear and tear is there on the transmission from not disengaging the hub?

 

For clarity, take 4L out of the equation since you can't actually shift directly from 4L to 2H, you have to go through 4H to get to 2H. When the hubs are locked the front CV shafts, differential, and driveshaft all turn regardless of what position the transfer case shifter is in. I would not worry much about wear to these components when running in 2H with the hubs locked, they are all seriously beefy components, similar to or stronger than the components in an R50 which has all that stuff turning all the time stock. (R50s came with drive plates rather than locking hubs.) You will lose a noticeable amount of gas mileage with all the front end stuff turning.

 

3) I can't think of any scenario why a driver would not disengage the hub when going from 4H or 4L to 2H? Why not take the few seconds to disengage the hub?

Maybe a driver would go from 4WD terrain to 2WD terrain, then back to 4WD terrain. If so, why not just leave it in 4WD short term and not risk wear and tear on the transmission

from driving in 2WD without disengaging the hub?

 

The place you will most commonly want to switch the T-case to 2H and back to 4H at speed is when there is spotty snow and/or ice on a paved highway. You do not want to run on dry pavement in 4wd, especially at speed as it puts HUGE loads on all the drivetrain components after the transmission. When you come to snow you stop (more below on this), lock the hubs by putting the truck in 4H, and proceed. If you're bombing along at 60mph on compact snow and come to a stretch of dry pavement you should shift to 2H just before the snow ends. Then when you encounter more snow drop it back into 4H just as you hit the snow.

 

You can shift from 2h to 4h on the fly up to 35mph.

 

While the manual says you can do this and the auto hubs will lock I do not recommend it. Often times one hub won't lock and will grind the living crap out of itself as you roll to a stop so it can actually engage. Auto hubs are not known for their durability and asking them to lock at speed is one of the roughest things you can do to them. When I ran auto hubs I always came to a full stop before the initial shift to 4H.

Edited July 21, 2012 by Mr.510

[Alkorahil]

 

While the manual says you can do this and the auto hubs will lock I do not recommend it. Often times one hub won't lock and will grind the living crap out of itself as you roll to a stop so it can actually engage. Auto hubs are not known for their durability and asking them to lock at speed is one of the roughest things you can do to them. When I ran auto hubs I always came to a full stop before the initial shift to 4H.

 

Totally agree!!!!

I always tell people that even though it says you can shift on the fly in the owner's manual....dont do it! Especially with the age now of the vehicles.

[Slartibartfast]

I shift on the fly, but only when it's already had a chance to lock up the hubs. On some days (winter) I'll start out in 4x to get out of the driveway, shift to 2x when I get to the road, and then shift in and out as needed. Until I back it up in 2x the hubs should stay engaged and it shouldn't cause problems. It clunks a little if I wait to engage it until I'm stuck, but it doesn't grind.

[Tungsten]

If you ever have to shift it on the fly, don't go very fast and shift it like you mean it. Stopping to shift is still a much better idea. It doesn't take long and saves the auto hubs from self destructing.

[jwblue]

If you ever have to shift it on the fly, don't go very fast and shift it like you mean it. Stopping to shift is still a much better idea. It doesn't take long and saves the auto hubs from self destructing.

 

I thought I was being too cautious about this.

 

I am glad other people feel the same way.

[Tungsten]

Forgot to add...

 

Never slam the hubs. Meaning do not get stuck with 2H and then shift into 4H and step on the gas. If you ever get stuck in 2H with the front hubs unlocked, shift into 4H and put it into D or 1st gear and just wait for the hubs to engage by themselves slowly. It's better to anticipate and lock the hubs ahead of time by shifting to 4H then back to 2H without reversing because then you could shift back to 4H with the hubs already locked.

[Slartibartfast]

^^That. I've actually done it a couple times to mine, nothing's exploded yet, but definitely something to avoid. It's tough to gently engage the hubs when, for the CVs to move (and thus for the hubs to lock), you have to spin the rears on ice/dirt/whatever. That's why I engage them in the driveway now if I suspect I'll need them at any point between there and where I'm going.

 

Gotta get me some manuals!