How To Use 4Wd?


Dear car gurus,

recently I started to explore more about the function of a 4wd system. As mentioned in other thread, I own a toyota prado TZ 3.0 and after searching from the internet, I learn that this is a full time 4WD vehicle (4wd come with differential lock).

The 4WD has 4 shifts: H, HL, N, LL and comes with standard auto transmission system (P, R, N, D, 2, L)

My daily use setting is engaged on the "H" and just put on "D" when driving.

When is the time to engage HL, N, LL?

I did test every 4WD shifts and learned that when shifted to HL, the rear wheel tended to skid. When shift to "N" and "LL" the car never move at all although I put my auto trans to "D-Drive". I tested it on the pavement road but with very slow speed (worry if spoil the trans case).

When I park my car (in "P" mode) and shift the 4WD to "LL", I noticed that the "A/T P" light is on. What does it mean?

When the mechanic warnned me not to try 4WD on the pavement road, I felt scared and never try it after that. But I dont feel satisfied untill I get to know how to use the 4WD.

Can any guru dont mind to teach a word or two?

Thanks.



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Hello,thought I'd reply to your questions seeing as no one else has tried to help although as I don't like either automatics or 4WDs I may not seem like the one to try to help.

Ah well, we'll see.

Ok,it's a full time 4WD which means it will have a centre differential unlike selectable 'part time' 4WD.

P,R,N,D,2,L : Park - for when you're leaving the vehicle. R - Reverse gear, N - Neutral for sitting in ques of traffic or at junctions (I imagine), D - Drive for standard driving, 2 - Drive 2 I think it uses two gears instead of the normal amount or perhaps it's more for economy driving, L - Low Range As in geared for more acceleration or possibly for towing trailers or caravans though that's a guess I'm afraid.


H,HL,N,LL - I'm guessing this stand for High, High Locked, Normal,Neutral?, Low Locked. Locked most likely refering to your centre diff which is often an option on full time 4WD vehicles that are designed to be capable Off Roaders.

Your mechanic is right to a certain degree but as you said it's a full time 4WD so you have no option but to always drive in 4WD. When he says not to try 4WD on the pavement road he must be referring to the HL and LL settings when the diff is locked.Driving on road with the centre diff locked is a BAD, BAD idea.

Full time 4WD cars can drive on the road specifically because they have that centre differential which allows the front and back wheels to turn at different speeds.This is required for everyday driving and cornering at typical road speeds.

It's also why when cars have part time selectable 4WD they should not be driven on road in 4WD because they don't have a centre diff.

The centre diff allows that difference in the turning speeds between the front and back wheels. Without it the fact that both axles are turning at the same fixed speed means that there will be extra stress and axle wind up during normal driving conditions like cornering and turning at speed.


When off road however the centre diff lock is of much greater advantage.

HL would be best used while driving on snowy,icy,muddy or loose gravelly surfaces where you would be off road driving at higher speeds.


LL for steep gradients,over rocky or rough surfaces where you're typically driving at much reduced speeds.When in Low Range there is greater torque delivered to the wheels but increased torque doesn't mean increased traction in fact on loose, slippery, icy, snowy and muddy surfaces greater torque will normally greatly increase the loss of traction.

Low Range is ideal for towing heavy loads or like I suggested on very rough off road surfaces i.e rocky,uneven or steep tracks.


Using HL on road will promote wheel spin and not advisable. Using N or LL probably has some failsafe in built designed so if you try to use it on road it automatically stops the drive going to the wheels and causing damage.


The N setting I'm unsure what it means Normal, Neutral??


As for the warning light A/T P it's simply letting you know it is in Park - Automatic Transmission Park. i.e you need to engage D, D2, L.

Anyway, I hope this helps a little.

 

I found this website 4x4abc.com quite interesting and with some useful articles.

 

 

 

 

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