How to use hi / lo.

[nickmcdonald]

Ugh.....I get the feeling im gonna get torn a new one for asking this...but here goes.....

I dont know how to use my 4wd Lo setting on my r50 terrano. Its a total soccer mum cruiser, and the only 4 wheel driving it really does is dragging my jet ski trailer up the beach.

I decided Id have a play before I left work. So with the engine idling in Park, I dragged the lever down from H, to N. A light on the dashboard showed up 'ATP', and the little lights showing which wheels are being driven disappeared. How does this differ from selecting neutral on the auto shifter?

I dragged it down to 4LO which is fairly self explanatory. I drove home normally, and decided to have a play up and down my street with the 4LO setting, just to see how it felt. But this time, the ATP light didnt come on when I put it into N...wierd? It also made some crunchy noises (gulp). Am I supposed to be doing this in Park or Neutral?

Be kind.....cheers.

[Crash bandicoot]

Don't be alarmed. I'm sure I was the first one to ever put my imported mistral into 4wd. it was damned tight at first but now you can engage 4H on the move and 4L in a jiffy. the ATP light will come on if the 2wd select lever is not engaged properly in N or one of the ratios. and if it's hardly being used at all be surprised if the light did go out as apposed to staying on.

as for selecting neutral on the transmission selecting neutral on the transfer case disengages the transmission/gearbox completely from the driveline.

[nickmcdonald]

Ah cheers Crash. So ATP means somethings not quite kosher. Sweet. So give me and example of when Id use the Neutral on the transfer case? Im struggling to think of a situation where Id use it?

I obviously havnt been using the transfer case, and my cousin who had the truck before me probably never used it, so I guess that may explain the tight shift feel and slight grinding noise? And its Park Im supposed to be shifting in right?

[Smurf]

You only use neutral when you don't want to go anywhere, it is the same as neutral in your gearbox.
No drive gets through the transfer to the driveshafts when the transfer is in neutral.
Although handy at night if you want good light behind you shutting a gate etc. handbrake on, put transfer in neutral and select reverse in gearbox, awesome torch light.

[Crash bandicoot]

You can't tow a conventional automatic car? why because if the trans is in neutral the wheels will still turn drive shaft which is connected to the output shaft of the transmission.

now neutral is fine in a auto vehical...but unlike a manual it isn't a total disconnection from the trans. the bands are still in contact and towing a auto with the engine not running will wreck them in a minute flat.

with neutral on a transfer case you can tow a automatic 4wd for example on an A frame behind a house bus. as above....it completely disengages the drive line from the transmission just like a manual gearbox.

As for the grinding, It only does that when there is load/tension on the drive line. i.e parked on an uneven surface.

[kiwipete]

One word of caution, do not drive on any sealed or concrete road/drive in 4WD as you can cause damage to it, you can bind up the drive line. Go out to a shingle road or similar and try there.

[nickmcdonald]

Ah cheers everyone, very enlightening information. Ill give it a whirl on the weekend and try and get the hang of it, on some gravel of course. Thanks again.

[imsohi]

[quote="Crash bandicoot"]You can't tow a conventional automatic car? why because if the trans is in neutral the wheels will still turn drive shaft which is connected to the output shaft of the transmission.

now neutral is fine in a auto vehical...but unlike a manual it isn't a total disconnection from the trans. the bands are still in contact and towing a auto with the engine not running will wreck them in a minute flat.

with neutral on a transfer case you can tow a automatic 4wd for example on an A frame behind a house bus. as above....it completely disengages the drive line from the transmission just like a manual gearbox. [quote]

Exactly right Towed a friends jeep out of lake daniells at Christmas auto lever in park and transfer in netural and it towed fine.

[The Stranger]

Ah cheers Crash. So ATP means somethings not quite kosher.

ATP should light when your transfer case is in neutral and your gearbox is in Park.
It is to warn that you actually have NO park as the driveshafts are now disconnected from the AT.

[haz77]

Can I just ask,

Why can you not drive a part time 4x4 on sealed roads when full time 4x4s obviously are fine?

I have used mine in 4x4 when towing heavy loads short distances down the road, is it seriously a major no no?

[mercutio]

fulltime 4wds have a diff in the transfer case which sends the power front to both front and rear wheels but shares it around so to speak whereas a parttime 4wd sends the same drive to both front and rear axles since both axles travel different distances this causes what is referred to as wind up in the drive line and can have serious consequences especially when driving on a sealed road it isn't so much of an issue on gravel roads as there is slippage in the gravel which allows things to unwind

[Dirtydog]

Can I just ask,

Why can you not drive a part time 4x4 on sealed roads when full time 4x4s obviously are fine?

I have used mine in 4x4 when towing heavy loads short distances down the road, is it seriously a major no no?

Comes down to how it is set up.

A typical full time vehicle has a center "Diff" which distributes the power to the front and rear, most have a center diff lock aswell for muddy situations.

Whereas a part time 4wd has no diff to differentiate the amount of power going to the front or back.

easiest way to explain it is this.

Fulltime 4wd (when center diff is not locked) = a Open diff
Part time 4wd (when in 4wd) = a locked diff

when you go around a corner with an open diff, the wheel turning faster is aloud to 'over run' the slower wheel, taking the harshness out of the drive train, but limiting traction as when power is applied to it, it takes the path of least resistance (i.e the wheel up in the air when 4x4ing)

The part time 4wd (when in 4wd hi or low) is like having that axle locked, so when turning a corner you have both wheels spinning at the same speed, bad news when that outer wheel wants to travel twice as far in the same amount of time. thats when stuff starts getting broken like axles etc.

although when the part time 4wd is in 4wd, it does give better traction because it is essentially a 2wd (when there are no lockers or lsd's) compared to 1 wheel getting the power.

Which is why most full time 4wd come with a center diff lock, to get better traction when needed.

I hope this helps in some way, im not the best at explaining things but i am trying.

[haz77]

Dont be so modest, very good explanations thanks, I now understand clearly how the system works and not to use 4x4 on seal unless its an emergency.

The main reason I have used 4x4 on limited occassions on short distances is purely that it makes for better towing of heavy loads nothing to do with traction, I guess the situation is then that if I cant pull it in 4x2 then its to heavy for the truck, good reason to tell the wife we need a bigger truck!

out of interest, are all part times set up like this or would newer vehicles have unlockable / selectable diffs?

[DieselBoy]

Range Rovers have had full time 4WD, and a lockable center did since the 70's

Basically, with a part time 4x4 system such as yours, don't engage 4WD unless you are on a loose surface.

If you do engage it on a hard surface, the transmission while wind up, the tyres will scuff and chirp and wear prematurely, the steering will get heavy and you risk serious transmission damage.

[Dirtydog]

In the older terrano's it can cause tie rods etc to bend aswell, which is a nuisance.

If you have manual locking hubs you can get away with putting it in 4wd lo , just dont engage the front hubs and youll still be in basiclly 2wd.

[lax2wlg]

A typical full time vehicle has a center "Diff" which distributes the power to the front and rear, most have a center diff lock aswell for muddy situations.

Which is why most full time 4wd come with a center diff lock, to get better traction when needed.

I thought the purpose of a centre differential lock was to maintain an even 50/50 torque split between front and rear, & that in pre-viscous coupling days, Land Rover recommended keeping it engaged at all times when offroad, to prevent power surging to one end of the vehicle and stressing it.

Its a myth that a centre diff lock adds any type of real traction advantage, it just keeps the power evenly distributed front/rear as the manufacturer intended. The final drive is still open, the same wheels are spinning, to me in the real world, this doesnt equate to any traction advantage.

[Dirtydog]

A typical full time vehicle has a center "Diff" which distributes the power to the front and rear, most have a center diff lock aswell for muddy situations.

Which is why most full time 4wd come with a center diff lock, to get better traction when needed.

I thought the purpose of a centre differential lock was to maintain an even 50/50 torque split between front and rear, & that in pre-viscous coupling days, Land Rover recommended keeping it engaged at all times when offroad, to prevent power surging to one end of the vehicle and stressing it.

Its a myth that a centre diff lock adds any type of real traction advantage, it just keeps the power evenly distributed front/rear as the manufacturer intended. The final drive is still open, the same wheels are spinning, to me in the real world, this doesnt equate to any traction advantage.

Well when you think about it, if most the power is going to the back of the vehicle (if it has open diffs all round) your really only getting one wheel drive, but if the center diff is locked its basicly becomes a 2wd.

Thats like saying an lsd doesnt give any real traction advantage.

[lax2wlg]

Well when you think about it, if most the power is going to the back of the vehicle (if it has open diffs all round) your really only getting one wheel drive, but if the center diff is locked its basicly becomes a 2wd.

Thats like saying an lsd doesnt give any real traction advantage.

Ok I get what you're saying, centre diff lock equalizes power front and rear, and smoother power delivery = better traction/driveability.

But re; LSD, I can't agree mate. LSD gives a direct traction advantage because it operates on the final drive - it attempts to redirect useful torque within one axle.

Just So theres no confusion on centre diff lock/locking differentials:

Ask ARB - Air Locker vs Center Diff Lock
http://www.arb.com.au/getting-started/ask-arb/air-lockers/020%20Air%20Lockers%20vs%20centre%20diff%20lock.php

[Dirtydog]

Im not saying that its the same as an lsd, im saying that it would give a similar benefit as having a lsd rear, with no center diff lock, ideally you would want a locker for both axles and the center lock, as it would potentially give 25% power at each wheel,

was merely dissagreeing that a center diff lock gave no real traction advantage, as having two wheels with power (one front one rear) is alot better than having only one (at the front or rear)

[rokhound]

A typical full time vehicle has a center "Diff" which distributes the power to the front and rear, most have a center diff lock aswell for muddy situations.

Which is why most full time 4wd come with a center diff lock, to get better traction when needed.

I thought the purpose of a centre differential lock was to maintain an even 50/50 torque split between front and rear, & that in pre-viscous coupling days, Land Rover recommended keeping it engaged at all times when offroad, to prevent power surging to one end of the vehicle and stressing it.

Its a myth that a centre diff lock adds any type of real traction advantage, it just keeps the power evenly distributed front/rear as the manufacturer intended. The final drive is still open, the same wheels are spinning, to me in the real world, this doesnt equate to any traction advantage.

This is exactly correct. A full time 4wd rig with the ctr diff lock engaged is exactly the same as a part time 4wd, in 4wd with hubs locked. I have know idea what DD was trying to say as it made my head spin......
A full time 4wd needs a ctr diff to stop full transmission wind up, as when cornering ALL THE WHEELS take a different track, and hence they all travel at different speeds.

[haz77]

So by that you should never drive a full time 4x4 on seal with the centre diff locked then?

[Dirtydog]

A typical full time vehicle has a center "Diff" which distributes the power to the front and rear, most have a center diff lock aswell for muddy situations.

Which is why most full time 4wd come with a center diff lock, to get better traction when needed.

I thought the purpose of a centre differential lock was to maintain an even 50/50 torque split between front and rear, & that in pre-viscous coupling days, Land Rover recommended keeping it engaged at all times when offroad, to prevent power surging to one end of the vehicle and stressing it.

Its a myth that a centre diff lock adds any type of real traction advantage, it just keeps the power evenly distributed front/rear as the manufacturer intended. The final drive is still open, the same wheels are spinning, to me in the real world, this doesnt equate to any traction advantage.

This is exactly correct. A full time 4wd rig with the ctr diff lock engaged is exactly the same as a part time 4wd, in 4wd with hubs locked. I have know idea what DD was trying to say as it made my head spin......
A full time 4wd needs a ctr diff to stop full transmission wind up, as when cornering ALL THE WHEELS take a different track, and hence they all travel at different speeds.

Im not good at explaining things....

So by that you should never drive a full time 4x4 on seal with the centre diff locked then?

I wouldnt say never, but it certainly is not a good idea.

[rokhound]

If you wouldn't drive your part time 4wd in 4wd with the hubs locked on the said surface, then no, you shouldn't drive an all time 4wd with ctr diff locked on those surfaces either. In some cases it is actually worse to drive with the ctr diff locked as a centre diff is quite often a lot weaker than a transfer case
(pointing finger at 90 series playdoh and kzn 185 surf....).
Transmission bind is really hard on components and it will blow apart the weakest link if given the chance.

[lax2wlg]

x2, good to get some factual accuracy here.

Using the centre diff lock on tarmac will actually cause drivetrain windup/bind, the exact thing it is designed to prevent on loose surfaces.

[churchill]

I'm splitting hairs here but an open diff provides a 50/50 torque distribution and a locked diff can provide 0/100 torque distribution to either side. If you have a truck with front and rear diffs locked (and center locked if it exists) and only one wheel is on the ground it will send all the torque to that wheel and none to the others hence 100% of the torque is going to that wheel.

[Dirtydog]

Not reading properly

[DieselBoy]

I'm splitting hairs here but an open diff provides a 50/50 torque distribution and a locked diff can provide 0/100 torque distribution to either side. If you have a truck with front and rear diffs locked (and center locked if it exists) and only one wheel is on the ground it will send all the torque to that wheel and none to the others hence 100% of the torque is going to that wheel.

Dirty Dog is wrong, you are correct.

[Dirtydog]

I'm splitting hairs here but an open diff provides a 50/50 torque distribution and a locked diff can provide 0/100 torque distribution to either side. If you have a truck with front and rear diffs locked (and center locked if it exists) and only one wheel is on the ground it will send all the torque to that wheel and none to the others hence 100% of the torque is going to that wheel.

Dirty Dog is wrong, you are correct.

Sorry didnt read that right, didnt relise you were talking about torque. whole different story.

[aotror]

Just to confuse the issue, If its the r50 terrano and a 3.2 diesel auto they have a switch on the dash that you can flick to the lock position which locks the center diff, or or some other setting, ("auto" i think it is called) where it is ok to use it in 4wd on the road. The car senses the need for 4wd and engages it when it needs to when in auto.
I hope thats the case as thats what i assumed when i had one, and used it like that.
I dont think the 2.7's have that as a standard option.

[Crash bandicoot]

Just to confuse the issue, If its the r50 terrano and a 3.2 diesel auto they have a switch on the dash that you can flick to the lock position which locks the center diff, or or some other setting, ("auto" i think it is called) where it is ok to use it in 4wd on the road. The car senses the need for 4wd and engages it when it needs to when in auto.
I hope thats the case as thats what i assumed when i had one, and used it like that.
I dont think the 2.7's have that as a standard option.

maybe not the 2.7 terrano, however in saying that my mistral (the 98 onwards x type) has it.