Towing up steep hill / diff wind question

[Lee argyle]

Originally Posted by John Kennett

I agree with all of that apart from the last bit

What would I know , I only run a 4x4 specialist garage (island4x4.net) and been a qualified off-road instructor for 15 years

[Lee argyle]

Originally Posted by Dhf

Seeing as the front and rear axles have different ratio's,
locking them with the transfer diff will cause one axle trying to overtake the other axle,
usually the rear has highest ratio, and this can have an effect on the steering on solid ground,
I've experienced it myself, its not like you can't steer at all, but it feels like somethings gonna brake if you keep going.

Never heard of that before, what vehicle are we talking about running different axle ratios.............

[paddlers]

My landrover 90 is a pig to steer on the hard stuff with the centre diff locked and I drive it almost every day !!! Spend hours in low box lamping with no issues!

[John Kennett]

Originally Posted by Lee argyle

What would I know , I only run a 4x4 specialist garage (island4x4.net) and been a qualified off-road instructor for 15 years

In that case I'll bow down to your immensely superior knowledge!

When I've needed to use 4WD with no centre diff on a hard road I haven't had any difficulty steering. Having said that it's not something I do very often for all the reasons that you gave. Does the steering only become affected once the transmission has got wound up?

[bedajim]

Stolen from Answers to your 4 wheel drive questions and off-road training by Harald Pietschmann.



If you own a vehicle with part time 4WD the need for different rpm front and rear represents a major problem. The transfer case will power the front and rear drive shafts with same rpm and is not able to satisfy the front axle's need for more rpm. Remember, the combined rpm of front wheels (A+B) is higher than the combined rpm of the rear wheels (C+D). Only full time 4WD systems are able to negotiate the needs of front and rear.

So, with part time 4WD engaged your front wheels are forced by good traction on the ground to rotate faster than the rear - but since the front drive shaft delivers only the same rpm as to the rear there is a fight between front wheels and rational force coming from the front drive shaft. The front drive shaft in effect tries to slow down the front wheels. This results in very wide turns (understeer) and dangerous handling on pavement.

The name "part time" derives from its use. It can only be used part of the time - most of the time (for most uses) it has to remain in 2WD. Only "full time" - notice the name - can be used full time for all uses.

The fight between front wheels and transfer case also makes 4WD performance suffer - the front wheels are not pulling like they should. They are in effect hindered by the front drive shaft.

The slowing effect caused by front wheels stresses all components between wheels and the transmission. It causes mechanical components to bind instead of moving freely - this situation is called "axle binding" ,"driveline binding" or "driveline wind up". First indicators while driving is a hard steering feel and the vehicle displaying jerky movement. Shifting back to 2WD will become impossible (gears and levers are extremely forced together). Continued 4WD use on dry surfaces will cause the weakest links to break (U-Joints, axles, differential gears, transfer case gears and chains, bearings, drive shafts).

When starting from a standstill with sharply turned wheels: The need for higher rpm in the front will most likely prevent you from getting started at all. If you step on the gas really hard (plus slipping your clutch) you might get the vehicle moving with spinning rear wheels but stress on all driveline components will be dangerously high. Chance is that you will break something.

When traveling with part time 4WD on high traction surfaces like asphalt, concrete, etc. handling of the vehicle will become unsafe (understeer) and the "driveline binding" will eventually cause component failures. Part time 4WD should not be used on high traction surfaces! Even when going straight most of the time, slight differences in tire pressure front to rear or vehicle load resulting in different axle speeds will cause "wind up" and eventually damage.

When traveling with part time 4WD on low traction surfaces like sand, gravel, mud, snow, etc. handling of the vehicle is unsafe (understeer) as well, but not as severe as on pavement. The slowed down front wheels simply skid a little on gravel, sand, snow, etc. during a turn. This in mind you should always approach difficult off-road obstacles in a straight line otherwise you might lose some of the much needed traction due to wheel slip on your front wheels.

Do not listen to guys who tell you it is OK to use part time 4WD on pavement! Severe damage will be the result.

Here is another important fact: Since front and rear axles are not able to rotate independently ABS will not work properly.

[Dhf]

Originally Posted by Lee argyle

Never heard of that before, what vehicle are we talking about running different axle ratios.............

Sorry Lee I was led to believe there's a number of different rear axle ratio's available for the L200,
and told the rear was higher for all 2wd option 4x4's, and this is what caused steering issues with diff lock,
so what is it in your proffesional experience, that causes the steering issue's in diff-lock?
I've had a few 4x's, Two LR's and three mitsi including the L200.

[Bigmuz7]

Originally Posted by bedajim

Stolen from Answers to your 4 wheel drive questions and off-road training by Harald Pietschmann.



If you own a vehicle with part time 4WD the need for different rpm front and rear represents a major problem. The transfer case will power the front and rear drive shafts with same rpm and is not able to satisfy the front axle's need for more rpm. Remember, the combined rpm of front wheels (A+B) is higher than the combined rpm of the rear wheels (C+D). Only full time 4WD systems are able to negotiate the needs of front and rear.

So, with part time 4WD engaged your front wheels are forced by good traction on the ground to rotate faster than the rear - but since the front drive shaft delivers only the same rpm as to the rear there is a fight between front wheels and rational force coming from the front drive shaft. The front drive shaft in effect tries to slow down the front wheels. This results in very wide turns (understeer) and dangerous handling on pavement.

The name "part time" derives from its use. It can only be used part of the time - most of the time (for most uses) it has to remain in 2WD. Only "full time" - notice the name - can be used full time for all uses.

The fight between front wheels and transfer case also makes 4WD performance suffer - the front wheels are not pulling like they should. They are in effect hindered by the front drive shaft.

The slowing effect caused by front wheels stresses all components between wheels and the transmission. It causes mechanical components to bind instead of moving freely - this situation is called "axle binding" ,"driveline binding" or "driveline wind up". First indicators while driving is a hard steering feel and the vehicle displaying jerky movement. Shifting back to 2WD will become impossible (gears and levers are extremely forced together). Continued 4WD use on dry surfaces will cause the weakest links to break (U-Joints, axles, differential gears, transfer case gears and chains, bearings, drive shafts).

When starting from a standstill with sharply turned wheels: The need for higher rpm in the front will most likely prevent you from getting started at all. If you step on the gas really hard (plus slipping your clutch) you might get the vehicle moving with spinning rear wheels but stress on all driveline components will be dangerously high. Chance is that you will break something.

When traveling with part time 4WD on high traction surfaces like asphalt, concrete, etc. handling of the vehicle will become unsafe (understeer) and the "driveline binding" will eventually cause component failures. Part time 4WD should not be used on high traction surfaces! Even when going straight most of the time, slight differences in tire pressure front to rear or vehicle load resulting in different axle speeds will cause "wind up" and eventually damage.

When traveling with part time 4WD on low traction surfaces like sand, gravel, mud, snow, etc. handling of the vehicle is unsafe (understeer) as well, but not as severe as on pavement. The slowed down front wheels simply skid a little on gravel, sand, snow, etc. during a turn. This in mind you should always approach difficult off-road obstacles in a straight line otherwise you might lose some of the much needed traction due to wheel slip on your front wheels.

Do not listen to guys who tell you it is OK to use part time 4WD on pavement! Severe damage will be the result.

Here is another important fact: Since front and rear axles are not able to rotate independently ABS will not work properly.

Makes sense now I was about to post earlier on this as I have had various 4x4's of which, some scrub tyres on a full lock, in low, and some dont, and I put it down to some electric wizardry of the central diff. I had an 04 plate Isuzu trooper that if in low 4, putting on a full lock whilst on concrete brought it to a complete stop, and you could tell it wasnt good for the transmission

[biffer]

Anyway to sum it up, use it

[Rokraider]

Diff ratios are usually the same front and rear. You can drive the vehicle on a hard surface in low range with no dramas, as long as it is in a straight line. If you turn the steering the front wheels will travel a different distance to the rear due to being able to turn in a tighter circle, that the rear cannot do. This will wind the transmission up and potentially damage the driveline. If you are driving in a straight line up the hill, you can use Low range.
Next time it snows or you are on a sandy beach drive your vehicle in a circle on full lock and look at the tyre patterns you leave, you will see 4 individual ruts, which illustrates why you need a differential to allow a vehicle to turn, each wheel has travelled a different distance.
There is a lot of confusion when the word difflock is mentioned. Some vehicles such as the Defenders, Discos and Older Range Rovers have a 3rd Diff in the transfer case that is able to be locked off road to stop the power all escaping to one axle or wheel. With the diff locked it splits it 50/50 front to rear. This is a very good setup, as it allows you to use Low Range on a grippy surface, without winding the transmission up, perfect for shunting heavy loads about or pulling a trailer up a steep slope.
You also get axle difflocks that allow you to lock the diff so equal power is sent to each wheel in that axle, so you would have equal power driving the wheel with the grip as the wheel with no grip, rather than losing all the power to the spinning wheel. With the axles locked you will have virtually no steering unless the tyre can slip.
To complicate things further, the Americans use different terminology to us. Over here, Part time would usually mean 4x4 on road and Full time would be the off road setting.
Part time in the USA means the off road setting and Full time means on road. Jeeps are a good example of this on their 4x4 controls.
Regarding the confusion over different diff ratios, you can change the ratios if for example you want to fit taller tyres, as they will raise the gearing. Normally you would do both diffs the same, unless you were running different tyres front and back

I have been selling and installing the ARB Airlocker since 1989 and their video explains things a bit better..
Air Lockers

[Chris Caton]

Originally Posted by biffer

Anyway to sum it up, use it

nicely put Biffer

[Jon Tallis]

Just be aware that if the climb involves any tight turns you will wind up the driveline (even though it's a centre difflock only). Particularly with a big load on there is a risk of breaking something, but that's probably balanced against a certainty of cooking your clutch if you have to do it in 'high'.

drop it in low and go easy on the gas

[Pikey Dave]

I'm sure some git said yonks ago that..........

Originally Posted by Pikey Dave

..............Diff lock will make it a bugger to steer around any corners unless there's some "slip" to be had.

[paddlers]

Originally Posted by Pikey Dave

I'm sure some git said yonks ago that..........

Lots of gits in Yorkshire, the place is full of them......

[Pikey Dave]

Originally Posted by paddlers

Lots of gits in Yorkshire, the place is full of them......

Aye! tha' not wrong

https://www.youtube.com/watch?v=pedAc8rQimw

[paddlers]

[mick]

Originally Posted by Pikey Dave

I'm sure some git said yonks ago that..........

ah but because you didn't use at least a 1,000 words and spend hours typing it out no one listens

[kerny]

Originally Posted by paddlers

Lots of gits in Yorkshire, the place is full of them......

[emoji2] [emoji6] [emoji106]

[HughN]

Originally Posted by Lee argyle

What would I know , I only run a 4x4 specialist garage (island4x4.net) and been a qualified off-road instructor for 15 years

You are right.

The only case when the front and rear axle might be travelling at more or less the same speeds is if the rear wheels were steering by the same amount as the front, i.e., four wheel steer. And the centre of gravity was dead in the middle of them. And all the tyres were the same. And the tyres were all at the same pressure.

You only have to see what the 'centre diff' of a Freelander does to the rear tyres...

[Peter_C]

Originally Posted by biffer

That's what the cars designed for, you're not running at speed or for a long way so it shouldn't do any harm whatsoever

You should see what a rock crawler goes thru with the diffs locked!

Tires scuffing and binding is not a problem as they will slip. Far less strain, then running over a rock and binding. The hardest part is going to be getting it out of 4lo and back into high gear. Drive straight, and back up if needed. You can gently let the clutch out in neutral, wait a second and ease it into a high gear. Turning the front wheels back and forth will also help unload the driveline.