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LJ70 - Engaging 4 wheel drive?

Carib

New Member
Joined
May 24, 2012
Messages
16
Would like some clarification on this...
I have a 1992 LJ70 SWB, 2LT engine, with manual front locking hubs.

Been bombing around the countryside and having a great time driving through shallow mud and up steep hills... I haven't had any problems until recently... went up the mountain past the snow belt line and got stuck. Rear wheels were spinning, front wheels not rotating.

Usually, I would press the '4H' button, the indicator on the dashboard would light up, and I would feel a noticeable difference when going through slippery or steep areas. I thought all was good. The guys I go wheeling with said they saw the front wheels 'spinning/pulling' the truck when in deep mud or on loose gravel.

However recently, up in the snow, the truck got stuck. '4H' was engaged, dashboard light was engaged, rear wheels spinning, but not the front.
I get out and manually turn the front hub (both sides) from "Free" to "Lock"... now the front wheels spin. Got out of the hole, and was on my way again.

Yesterday, got stuck in some deep mud. '4H' was engaged, front hubs were in the "Free" position. Rear wheels spinning, front wheels doing nothing. After putting it in the "Lock" position, the truck ploughed through everything.

Here's my train of thought...
- Pressing the '4H' engages the front drive shaft and makes the front wheel spin...
- Turning the front hubs from "Free" to "Lock" causes the fronts hubs to lock and spin at the same rate and so help create more traction
- 4H is to be engaged when at a standstill and gearbox in neutral (my truck has a 5sp manual gearbox).
- After moving hubs from "Lock" to "Free", the hubs and 4H would not disengage until I reverse a little, otherwise the '4H' light on the dashboard blinks (noticed from experience)

I can't look up the operation of the system in the owner's manual as it's in German (my truck was imported from Germany). Tried searching, but a lot of info out there is regarding the electronic locking hubs.

Can anyone please shed some light on the operation of the drive system that is equipped with manual front locking hubs?

Thanks,
Carib.
 
The reason for the truck having manual locking/unlocking hubs is to aid economy, by unlocking the hubs ('free') you are removing drag from the drivetrain, so should get better mpg.

In normal 2H your transfer box is only powering the rear diff/axle, hence the rear spin and the front do nothing.

If you put the transfer box into 4H but have the front hubs on 'free', you are powering the front as well, but if 'free' is selected the hubs arent connected to the prop, so the prop will spin but the wheels wont!

Hence when selecting 4H you need to engage 'lock' in order to have 4wd.

If you are going to attempt a climb/mud run or whatever, you need to stop and engage the hubs and 4H. You could leave the hub locked all the time, running in 2H means they wont be powered, although you will see a slight drop in mpg due to drag.

It is normal to have to reverse in order to free up the transfer box in part time 4wd models. Even full time 4wd need this when trying to disengage the low box.

Obvious point, dont drive your truck on a hard or non-slippery surface when in 4H, you will get a 'wind up' in the box, which will go ping.

Cheers

Pete
 
Okay, so let me see if I understand this...

1) To get all 4 wheels powered, "4H" needs to be engaged AND the manual front hubs in the "Lock" position.

2) The truck can be operated (when offroad, i.e. gravel, mud, snow, dirt, shallow streams, rocky roads, etc) with the front hubs in the "Lock" position and the '4H' operated (on/off) as seen fit, e.g. 2H on level dusty/slightly rocky paths and then 4H going up steep rocky hill (front hubs in the "Lock" position all the time)

3) The trans will wind up if driven with hubs in the "Lock" position AND on paved roads. Fairly obvious and logical.



One more question, is there any serious negative effects, other than increased drag, if the hubs are left in the "Lock" position and drive while in 2H on paved roads? Not saying that I do that or will, just curious....
 
Many of us just leave the hubs locked in all the time, especially in Winter. That way you only need to press the button to get 4wd. Never noticed any difference in fuel consumption myself.
 
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Many of us just leave the hubs locked in all the time, especially in Winter. That way you only need to press the button to get 4wd. Never noticed any difference in fuel consumption myself.

with your hubs already locked the beauty is that you can then engage your 4WD on the fly. Good practice though is to have the steering straight and just let of the gas a touch so that your drive train is unloaded when you engage it.
 
I'll give that a try... I was always a bit paranoid about engaging the 4H while rolling slowly.
 
Okay, so let me see if I understand this...

1) To get all 4 wheels powered, "4H" needs to be engaged AND the manual front hubs in the "Lock" position.

Correct

2) The truck can be operated (when offroad, i.e. gravel, mud, snow, dirt, shallow streams, rocky roads, etc) with the front hubs in the "Lock" position and the '4H' operated (on/off) as seen fit, e.g. 2H on level dusty/slightly rocky paths and then 4H going up steep rocky hill (front hubs in the "Lock" position all the time)

Correct. The system relies on an amount of wheel slip to stop the system winding itself up, so going up a steep rocky hill you will probably lift a wheel occasionally, this allows the necessary 'unwinding' to occur.

3) The trans will wind up if driven with hubs in the "Lock" position AND on paved roads. Fairly obvious and logical.

Correct



One more question, is there any serious negative effects, other than increased drag, if the hubs are left in the "Lock" position and drive while in 2H on paved roads? Not saying that I do that or will, just curious....

The only negative effect will/may be a slight drop in economy.

I assume you have an electric locking hub button? If you only have manual hubs (ie no power button) shifting on the fly would be very interesting indeed :icon-biggrin:

If you do, add in 'press the button' between 'lock the hub' and 'select 4H'......

Cheers

Pete
 
The only negative effect will/may be a slight drop in economy.

I assume you have an electric locking hub button? If you only have manual hubs (ie no power button) shifting on the fly would be very interesting indeed :icon-biggrin:

If you do, add in 'press the button' between 'lock the hub' and 'select 4H'......

Cheers

Pete

You have lost me a little here Pete. He doesn't have electric hubs, just good, old fashioned but reliable manual ones. Shifting on the fly from 2 wd to 4 wd by use of the 4 wheel drive button is ok, as long as you have your hubs locked in. Toyota recommend that you are driving in a straight line at a speed less than 62 mph. If you try to engage 4wd without the hubs being locked in, damage is inevitable. As John has pointed out, a lot of drivers leave the hubs locked in permanently. I have junked the hubs and fitted solid flanges.

Roger
 
Definitely have manual locking hubs in the front.
Fully aware now that the hubs have to be in the "Lock" position for the front wheels to be engaged when in 4H
Even though I'm know you can switch on the fly between 2H and 4H (with the hubs locked), I will continue my practice of switching between 2H and 4H and subsequently 4L when at a standstill... It's a habit that will die hard :)
 
Here's a scenario that may change your mind.

If you attempt to drive through a deep puddle or flooded road in 2 WD i.e. rear wheel drive, the front end will be very skittish, even to the point of you loosing control but if you select 4 WD before you hit the water, your stability will be maintained.If you switch of the 4WD after the puddle/flood, you wont get axle wind up and no damage will be sustained.

Roger
 
Will keep that in mind.... and will have to put my manual front hubs in the "Lock" position first...! My slow driving hasn't allowed me to experience having the front end lose grip or get skittish (except in the deep snow) as yet despite having driven in and through deep puddles and flooded roads.
 
One other thing to consider with manual free wheeling hubs and driving in flooded areas is when crossing deep water if the truck starts to float the rear end goes first, if you dont have the hubs locked then you cannot select 4x4 meaning you have no drive unless you get out and lock the hubs which I cant imagine would be fun in deep water while the truck is drifting!

Personally I drive with the hubs locked throughout the winter and during bad weather/road conditions and only unlock them for long motorway trips in the summer.
 
One of the reasons for my decision to fit solid flanges---off an 80 series---was that the local low life had a tendency to switch off one of my hubs. The solid flanges remove this problem and give me peace of mind.

Roger
 
Peace of mind is a good thing to have. Might go that route with the solid flanges in the future. For now, I haven't had the misfortune of dealing with people tampering with the hubs.
 
This thread has totally confirmed all of the things I was trying to work out in January. I was having exactly the same issues as Carib in the snow and didn't know about the locking front hubs. I've had no problems engaging the 4WD whilst rolling slowly and going straight. I'm quite sure that a lot of this will be a learning curve - my first 4x4 and a 1989 one at that. I love it more and more each day though. Excellent response from Wobbly :)
 
A recent test by a 4x4 magazine in Australia, reported no discernible difference between hubs locked and unlocked with regard to fuel consumption.

Roger
 
Roger, I know that the 70 and 80 are different beasts, but did my usual trip to Scotland recently with no front prop, no diffs and no halfshafts - everything else the same, and my economy was WORSE. It was discernibly different to drive and I think that not having the front traction in bends and on roundabouts sapped power. I couldn't wait to get my front diff back in.

I think this bears out the evidence in the report. I don't profess to know anything about the 70 drive train, but the 80's is certainly very well mated and there is no fighting going on with the full time drive line. I know that other vehicles have a less well set up system and being in 4x4 on the road could certainly mean a drop in economy due to those in built resistances. I would think that the 70 is a similar set up to the 80 - no? So driving with components locked probably really doesn't make much difference.
But it does sort of beg the question, why did Mr T make it selectable? Does it feel different to drive at all?

C
 
Interesting point Chris.

The magazine tested the vehicles over a cross country run that included dirt tracks. They concluded that the stability afforded by 4 wheel drive as opposed to just rear wheel drive does help to claw back any losses that may be occasioned by having 4 wheel drive.

The 70 series uses a part time 4 wheel drive system. I fitted 80 series flanges to ensure that 4 wheel drive is always available to me by pressing the 4 wheel drive button on the dash. It's perfectly ok to use 4 wheel drive on a sealed road for a short distance. Situations such as a deep puddle where only your nearside wheels will enter the water are ideal candidates for doing this. Without 4 wheel drive you stand the chance of the motor pulling hard to the left and control being lost.

I am at a loss to understand why Toyota used a part time system. The 90 series went back to permanent 4 wheel drive, so maybe they had learnt a lesson. I don't see cost being the answer as the 70 series needed the manual locking hubs, or even worse, the electrical ones. From memory the 90 used solid flanges and a viscous coupling.

Many of the problems associated with 4 wheel drive systems is the lack of knowledge, on the part of the driver, as to how the various systems work and how to get the best out of them.

Roger
 
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