When is Four Wheel Drive engaged?

[DiscoDave]

My Series I has all the 'normal' gear levers for a series Landy (without PTO or overdrive) - black, yellow and red. In a Series III, as I understand it, low ratio is always 4WD but in high ratio 4WD only operates if you press the yellow lever. However reading through the operating manual for 48-51 Land Rovers it talks about engaging the "Front Wheel Drive Lock" (the yellow lever) which can only be engaged when in LOW ratio. This locks the "overrun freewheel unit". In high ratio "when the engine is coasting with the vehicle travelling forward drive is to the rear wheels only".

This sounds like a different system entirely to the Series III or have I got it wrong? When does my Series I have 4WD engaged?

[101RRS]

Are you talking about the very early series 1 with constant 4wd via the flywheel thingy or your 86. Your 86 will operate the same as any other series - push down to engage 4wd, pull back the lever to engage low range etc

I assume for the early flywheel ones it as you read in the handbook

Garry

[DiscoDave]

So there was a redesign of the 4WD system between '51 and '54?

[101RRS]

I believe so - sometime around 50/51 but I am not sure - others more knowledgeable than I will no doubt give the right answers.

Garry

[JDNSW]

The first Landrovers were constant four wheel drive, with the front axle (equipped with Tracta CV joints) driven via a free wheel unit (same as was used on some Rover cars). Since this would mean that there would be no drive on the front axle in reverse, the free wheel unit could be locked by a pull ring on the floor near the High-low lever.

This was replaced fairly early by the familiar yellow knob to operate the lock, disengaged by engaging and disengaging low. (can't lay my hand on a date)

The free wheel and the CV joints were replaced about 1951 by the familiar part time four wheel drive system that remained unchanged except for details until the early 110s.

John

[DiscoDave]

Thanks to both of you for clearing that up for me. :)

[UncleHo]

G'day DiscoDave:)

The first of the Series 1 80" inch vehicles had the "Ring Pull" gearbox transfer units, that was in use by Rover from about1932 in various forms, the 1951 models (late50 onwards) were the first to use the Selectable Four Wheel Drive system,(although the records suggest that the last 1950 models had these transmissions fitted) and the larger 7"inch Headlights, the parking lights (side lights) were moved to the Guards(wings) in the Spring of 51.

cheers

[Roverray]

Just for the record my 1950 has the tractor headlights side lights on F/wall but the later T/case ---yellow knob!

[JDNSW]

Just for the record my 1950 has the tractor headlights side lights on F/wall but the later T/case ---yellow knob!

Some at least of the free wheel front drive systems used the yellow knob instead of the ring pull to lock the front drive. But since the transfer case is interchangeable, what it has now is not necessarily what it came from the factory with.

The free wheel unit is quite different in appearance (tapers forward rather than parallel is the easiest way of describing the difference) from the later transfer case extension housing, so it is easy to tell which you have by looking underneath.

John

[101RRS]

Can someone explain how this flywheel 4wd system works? I know that one of its disadvantages is that it didn't work in reverse - why? and why were the advantages over the simple diff system used in later landies.

Thanks

Garry

[Blknight.aus]

ITs sort of a one way sprag clutch that drives the front axle and it was setup so that when the back wheels slipped the front wheels would recieve drive from the sprag. IT was lockable with a sliding collar which is what the ring was for.

And its a freewheeling unit not a flywheel..

[101RRS]

ITs sort of a one way sprag clutch that drives the front axle and it was setup so that when the back wheels slipped the front wheels would recieve drive from the sprag. IT was lockable with a sliding collar which is what the ring was for.

And its a freewheeling unit not a flywheel..

Thanks - I guess I need to google what a sprag clutch is.

[Blknight.aus]

Nahh, its a one way clutch. When torque is applied in one direction it is transmitted when applied in the other direction nothing...

Theres 3 or 4 different types that do the same thing in about the same ways with different minor advantages...

But delving into them here would be a hijack.

[101RRS]

OK looked it up and I think I understand - so the car was not constant 4wd as douted but rear wheel drive and when the rear wheels slipped, so turning faster than the front wheels the sprag clutch activates engaging the front wheels.

I was confused because the early landies were marketed as constant 4wd when they were rear wheel drive with an automatic on demand awd system - while the mechanicals are different the result is the same as the Viscous Coupling fitted range rovers (rear wheel drive and only AWD when the rear wheels slip) and the Freelander being front wheel drive and only awd with full torque to all wheels when the front wheels slip.

Cheers

Garry

[Blknight.aus]

you need to remove two words from your post....


the I think....

Mate for a lay description youve nailed it.

[JDNSW]

OK looked it up and I think I understand - so the car was not constant 4wd as douted but rear wheel drive and when the rear wheels slipped, so turning faster than the front wheels the sprag clutch activates engaging the front wheels.

I was confused because the early landies were marketed as constant 4wd when they were rear wheel drive with an automatic on demand awd system - while the mechanicals are different the result is the same as the Viscous Coupling fitted range rovers (rear wheel drive and only AWD when the rear wheels slip) and the Freelander being front wheel drive and only awd with full torque to all wheels when the front wheels slip.

Cheers

Garry

NO. They are full time four wheel drive, with both front and rear wheels driven at the same speed. When driving straight all wheels are driving. When turning, because the front wheels take a longer track, the rear wheels only drive unless the rear wheels slip, in which case the front wheels drive as well. Effectively (forwards only not reverse) it is the same as a locked centre diff or selectable four wheel drive engaged, not like a viscous coupling, as it does not allow power to be given to front and rear axles turning at different speeds.

The advantages over a centre diff were:-

1. No need for a separate lock except for reverse.

2. The free wheel unit was already in production in the company, reducing tooling costs.

The reasons for dropping it have never been explained that I know of, but were probably because the free wheel unit in this application proved less than reliable, possibly because the setup allowed full low range torque to be applied to the rear drive during turns intermittent gripping of the rear wheels could then put high shock loads on both the free wheel unit and the rear diff and drive shaft.

John

[Lotz-A-Landies]

This sounds like a different system entirely to the Series III or have I got it wrong? When does my Series I have 4WD engaged?
Dave

Sorry for coming to this thread very late, but I have been lazy or busy or something. (Or feel treasonous :wasntme:)

Yes the early Series 1's had a different 4 wheel drive system. In fact they were actually a full time four wheel drive with an integral freewheel unit on the front output shaft which allowed the front propellor shaft to rotate faster than the rear one. This only happened when cornering, where the front outside wheel takes the longest path so rotates faster to cover the distance until the end of the corner where all wheels are traveling in the same direction at the same speed and drive is applied equally to all wheels.

The issue came when you wanted to have 4wd in reverse. In this case the freewheel unit needed to be disengaged (or locked) into 4wd.

From the begining of the 1948 production model to gearbox number 06104014 (VIN 06103884) in the early part of the 1950 model the freewheel lock was actually a small metal ring recessed into the floor on the RHS of the gearstick behind the transfer box lever. At gearbox number 06104015 the "ring pull" was replaced by a yellow knob that looked the same as ther later yellow knobs on the part-time 4wd transmissions. The function remained the same as the ring pull chain to engage 4wd in reverse.

The selectable part-time 4wd transmission came early in 1951 at gearbox number 16102314 (note that in 1951 there were multiple destination codes so the gearbox number is the best guide.)

Onto the body styles the first of the yellow button/freewheel unit models still had the headlamps behind the grill and the wide transom with the "sprung shovel" shaped seat backs although the "fishplate" that held the bumper bar on had been replaced by the later style bar where the mounting brackets were now part of the bar. By the introduction of the part-time selectable 4wd transmission, the Land Rover had the 7" Lucas headlamps, the spade shaped folding seat backs and the 2 1/4" wide front springs with the shackles at the rear of the spring. So essentially the elements that remained to the end of Series 3 production.

Hope this helps. :cool::cool::cool::cool:

Regards
Diana

[scrambler]

To go back a bit - a freewheel is what the drive hub of most road bicycles have, allowing drive to be applied in one direction only (forward) while the wheel can travel faster than the drive chain (or shaft in the case of a Series I).

One implication not mentioned yet is that engine braking in an early Series I would only transmit to the rear wheels, making driving down a steep slope a rather interesting idea.

[Blknight.aus]

actually I was going to suggest the simple is it all wheel drive or not test....

jack up all wheels one at a time with the vehicle in gear, park brake off and see if you can spin the wheel in each direction...

IF you only move all 4 wheels far enough to take up driveline slack you have a full time 4 wheel drive.

If a wheel can be rotated freely its not a full time four wheel drive.

The early S1 fails this test as you can freespin the front wheel forwards when the freewheel lock is not engaged. In realitly the only time this might happen is if you are doing a steep descent under engine braking (which means you should have the freewheeler locked up anyway) and the backs break away. (as previously mentioned.

[scrambler]

Perhaps it could be said that the early Land Rover arrangement is full-time 4 wheel DRIVE but not full-time 4 wheel ENGINE BRAKING?

[JDNSW]

1. To go back a bit - a freewheel is what the drive hub of most road bicycles have, allowing drive to be applied in one direction only (forward) while the wheel can travel faster than the drive chain (or shaft in the case of a Series I).

2. One implication not mentioned yet is that engine braking in an early Series I would only transmit to the rear wheels, making driving down a steep slope a rather interesting idea.

1. Patented 1869, first mass produced 1898 by Ernst Sachs for use on bicycles.

Free wheel units were commonly included to the rear of the gearbox in up-market cars, particularly from the UK, in the 1930s. This is because with free wheel, almost as soon as you disengage the clutch, the gearbox will stop rotating, enabling an easy, noiseless change to any gear without needing synchromesh - and the clutch engagement will be smooth as well, since the drive will not be taken up until the gearbox output shaft is going as fast as than the tailshaft. Rover was fitting freewheel units to their cars from 1932.

2. The freewheel lock was provided to enable front wheel engine braking as well as four wheel drive in reverse.

John

[Blknight.aus]

Perhaps it could be said that the early Land Rover arrangement is full-time 4 wheel DRIVE but not full-time 4 wheel ENGINE BRAKING?

ahh but what about reverse and cornering?

would it not be more accurate to say that Its a full time four wheel drive unless your engine braking, reversing or cornering?

wouldnt it be easier to say its a part time fourwheel drive?

:angel:

[wrinklearthur]

The 80" that AlexH has just acquired, has a free wheeling transfer box and the yellow knob to lock the free wheel device.

On our joy ride around my paddock we headed down the steepest bank a-n-d away we went!!!! :twisted:

It looks like to me that the locking mechanism isn't doing it's job as the rear wheels skidded from top to bottom.

What should we be looking for in possible broken and/or missing parts?
.

[dennisS1]

No it is doing its job the front wheels can turn faster than the back, If you turned around and tried to drive up the hill at least 1 front wheel and 1 back would spin, just like any new constant 4WD.
The traction control is not that good or I can’t find the switch on my 48.
Dennis

[back_in]

Dennis
I though you knew were the Traction Control was on a 48/49
it is called your right foot
you doing the Bay to Birdwood this year?
about time you blew the spiders out of the 1957 waggon
cheers big fellow
Ian