Diff locks (operation)

Michael H. · Feb 8, 2024

j3t3r said:
Can you really lock the center dif at speed? I thought neutral had to be engaged first (obviously can still be rolling in neutral)

My understanding (and experience) is that it can be locked on the move, up to 40km/h.

j3t3r · Feb 8, 2024

Michael H. said:
My understanding (and experience) is that it can be locked on the move, up to 40km/h.

Do you engage your center diff in drive, or always switch gear into neutral first ?

Michael H. · Feb 8, 2024

j3t3r said:
Do you engage your center diff in drive, or always switch gear into neutral first ?

I’ve been locking the centre diff in Drive (up to 40km/h) although I would note that in the Getting to Grips with your Grenadier video, the instructions are to stop and engage Neutral before shifting.

Tinerfeño · Feb 8, 2024

If there is no wheel slip and you are not cornering I can't see need for any speed limit.
I've locked CDL and connected partial 4WD on parctically all my cars at ~80 km/h (normal winter speed limit in Finland).

Tazzieman · Feb 8, 2024

Michael H. said:
I’ve been locking the centre diff in Drive (up to 40km/h) although I would note that in the Getting to Grips with your Grenadier video, the instructions are to stop and engage Neutral before shifting.

NA manual: "The center differential can be locked and unlocked with the transfer case selector while on the move so long as the axles are rotating at the same speed"

Dirt road , snow etc, no problem. Mine shifts easily at 60km/hr. Same as with old LR , Disco
Rough terrain - stop first

Logsplitter · Feb 8, 2024

You can engage centre diff lock whilst moving at low speed but to change between high and low you need to be in neutral and stationary.

Tazzieman · Feb 8, 2024

Logsplitter said:
You can engage centre diff lock whilst moving at low speed but to change between high and low you need to be in neutral and stationary.

Indeed. As the manual states (always read the manual , even if it has been written in a peculiarly wordy way!)
"Range changes require shifting to N(Neutral) on the automatic transmission."

Tinerfeño · Feb 8, 2024

Tazzieman said:
Rough terrain - stop first

Or even better: lock before entering

Tazzieman · Feb 8, 2024

Tinerfeño said:
Or even better: lock before entering

I shift on the bitumen just before I hit the dirt , otherwise my wife chimes in to remind me!

klarie · Feb 8, 2024

Tazzieman said:
I shift on the bitumen just before I hit the dirt , otherwise my wife chimes in to remind me!

In my area its like so - bitumen -> Gravel -> dirt. On Gravel I leave centre diff unlocked but when moving towards the dirt the centre lock will be set while in motion. Unlock the same.
High Range to Low range and vice versa always in neutral and no motion.

K1LL3M · Feb 8, 2024

Regarding CDL, understanding what, may help with why.

The Grenadier is full time 4wd. Meaning in a straight line the front and rear prop shafts are spinning at the same speed. So long as they are, engaging the lock is not a problem as you are connecting them together, so they cannot spin separately

If they are not spinning at the same speed, eg if it was not a fulltime 4wd, you are turning or spinning wheels or powering through something, the CDL would shock load the systems, causing serious damage

The speed limit on the change, is predominantly to cover if there is any minor variation in speed between the front and rear, it should not be that great, but it is why you should not be turning or accelerating when engaging. Constant straight line speed no worries, or stop and engage

Low range, you're changing gear ratios, engaging reduction gearing, clearly doing this while moving is not going to be a good day.

Miki · Feb 8, 2024

The central diff lock is essentially a spring loaded pin that lock both outputs of the transfer box together. Power is distributed evenly to both propshafts/axles when it is engaged.

In simple terms. To engage a spring loaded pin is pushed into a hole, to disengage the 'push' is removed and the spring draws the pin out.
To get the pin in the holes have to line up and to allow the pin to get out there mustn't be any sideways grip on the pin.

The holes are in alignment when the front and rear axles are rotating at the same speed.
In this happy state the pin can be pushed in and will pull out easily.
Sometimes just lifting your foot off the accelerator (so the car is rolling) will be enough to release any pressure in the diff and it will lock/unlock easily, braking accelerating and cornering will all create pressure on the pin stopping it moving (in or out).

If you leave the pin in and drive around on the road (or other grippy surface) with the CDL 'locked' then you will increase the pressure on the propshafts which may damage the diff.
Modern locks are better than the older versions, for example in the older Land Rovers you would often need to stop and reverse for a few yards to get the CDL pin to spring out and disengage the CDL.

K1LL3M · Feb 8, 2024

Miki said:
The central diff lock is essentially a spring loaded pin that lock both outputs of the transfer box together. Power is distributed evenly to both propshafts/axles when it is engaged.

In simple terms. To engage a spring loaded pin is pushed into a hole, to disengage the 'push' is removed and the spring draws the pin out.
To get the pin in the holes have to line up and to allow the pin to get out there mustn't be any sideways grip on the pin.

The holes are in alignment when the front and rear axles are rotating at the same speed.
In this happy state the pin can be pushed in and will pull out easily.
Sometimes just lifting your foot off the accelerator (so the car is rolling) will be enough to release any pressure in the diff and it will lock/unlock easily, braking accelerating and cornering will all create pressure on the pin stopping it moving (in or out).

If you leave the pin in and drive around on the road (or other grippy surface) with the CDL 'locked' then you will increase the pressure on the propshafts which may damage the diff.
Modern locks are better than the older versions, for example in the older Land Rovers you would often need to stop and reverse for a few yards to get the CDL pin to spring out and disengage the CDL.

A bit more than a pin in a hole, eg locking collars and stuff, but close enough

nuclearbeef · Feb 8, 2024

Mountain4x4 said:
Automatic lockers are for mild use. They lock and unlock at will, they are not ideal. In the case of the GM G80 almost useless. Manual lockers are next level. Want top level? The Power Wagon has a rear manual locker that acts as an LSD when off.

200 Land Cruiser has a Torsen limited slip center diff that is also lockable.

Miki · Feb 8, 2024

nuclearbeef said:
200 Land Cruiser has a Torsen limited slip center diff that is also lockable.

I want one of those in my Defender .... Ashcroft (in the UK) do one for the LT230, costs about £1000 + fitting.

255/85 · Feb 12, 2024

nuclearbeef said:
200 Land Cruiser has a Torsen limited slip center diff that is also lockable.

But no factory front/rear lockers. It will run you somewhere in the neighborhood of $5K USD to get them aftermarket.

Mountain4x4 · Feb 13, 2024

nuclearbeef said:
200 Land Cruiser has a Torsen limited slip center diff that is also lockable.

Thats a center diff, which is fine but that is AWD for street use. A rear differential that acts as an LSD when off allows you to travel further off road before having to lock up, which is nice. Frankly the Power Wagon needs it due to weight going up hills. But I believe Rubicons have it as well.

nuclearbeef · Feb 13, 2024

Mountain4x4 said:
Thats a center diff, which is fine but that is AWD for street use. A rear differential that acts as an LSD when off allows you to travel further off road before having to lock up, which is nice. Frankly the Power Wagon needs it due to weight going up hills. But I believe Rubicons have it as well.

"acts as an LSD" confused me. I figured it was not a mechanical LSD, but electronic, using brakes.
Looked it up. Power Wagon has a "Torsen-style" mechanical LSD rear diff that is also lockable. Same as LC center diff.

Personally, I never use any traction aids until I start losing traction. This way, if I get stuck in 2wd, I can then pull out the big guns, engage 4wd and unstick myself.
Center diff open and start to slip... Lock center; extract self.
Open front, rear... You get the idea.

This might have to do with my local terrain. Mud is the only obstacle I regularly deal with.
Need to cross this field to turn on a pump?
Bad idea to start that adventure with all traction aids on only to bog yourself down to the frame a mile from the nearest tree.

bemax · Feb 13, 2024

nuclearbeef said:
"acts as an LSD" confused me. I figured it was not a mechanical LSD, but electronic, using brakes.
Looked it up. Power Wagon has a "Torsen-style" mechanical LSD rear diff that is also lockable. Same as LC center diff.

Personally, I never use any traction aids until I start losing traction. This way, if I get stuck in 2wd, I can then pull out the big guns, engage 4wd and unstick myself.
Center diff open and start to slip... Lock center; extract self.
Open front, rear... You get the idea.

This might have to do with my local terrain. Mud is the only obstacle I regularly deal with.
Need to cross this field to turn on a pump?
Bad idea to start that adventure with all traction aids on only to bog yourself down to the frame a mile from the nearest tree.

It is a fair approach. But you should think about locking the central diff anyway in slippery areas as it (unlocked) might suffer from spinning axles. @AWo explained somewhere why this can be important.

AWo · Feb 13, 2024

Diff locks or not?

Having been stuck too many times in a 100 series Landcruiser with the centre diff lock on, I would posit that any vehicle without locking diffs (or at least a limited slip diff) is not a true off-road vehicle. I also have a 2-wheel drive Mazda BT-50 (used to carry a slide-on camper) with a rear...

www.theineosforum.com

BTW, pictures showing the result of not having the center diff locked. They show one half of a center diff housing. That's why I use a Torsen in the center diff (as in the rear axle).

AWo

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Diff locks (operation)

Michael H.

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Diff locks or not?

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