Question about diff locks

[Ayahuasca]

I have a Toyota Prado, automatic, and the option of putting the 4WD into L, LL, H, HL. I understand that the HL and LL apply a central diff lock.

Now, as I understand it, the central diff lock ensure that power is distributed 50/50 between front and rear axles, but NOT equally between the wheels on a single axle.

Which means that - please correct me if I am wrong - if one wheel on each axle loses traction and spins, the other wheel on that axle will not move, so effectively the car goes nowhere.

Is that right?

If so I am beginning to understand why I got stuck at the weekend, but failing the understand the point of a central diff lock!

[thescamper]

You are correct in your assumption.

[normalbloke]

If you didn't have a central difflock, you effictively only have a true 1 wd car.You could have one wheel in the air or the mire and it would stop the car dead,as the open centre diff and axle diff would allow all power to be transferred to the wheel with least resistance.
Make sense?

[Ayahuasca]

Ta, makes perfect sense now.

Do you know if it is possible to retro-fit an axle diff lock?

[OnTheOverrun]

Ayahuasca said:

Ta, makes perfect sense now.

Do you know if it is possible to retro-fit an axle diff lock?

Very possible!

You can fit the 'fit and forget' types like a truetrac LSD or detroit locker which do the job automatically or you can fit ones like ARB air lockers.

Truetracs are good and don't affect on road performance but don't lock up completely so don't suit very heavy duty off-roading but do maintain steering. Detroit lockers actually work in reverse - ie they don't lock the axle when slip is detected, they are constantly locked but unlock when you corner. They can be a bit snatchy and a liability on ice.

The ARBs are simple axle lockers you operate manually from the dashboard. The downsides are they need a compressor installing and the air pipes down to the axle can be vulnerable. Remember with your front diff locked you will have limited steering which can be fun!

My personal choice is a truetrac up front and a detroit in the back, a setup I ran very successfully in a 90 V8 for many years.

[normalbloke]

I'll second the Detroit products.I have a CJ7 with the 5.9 AMC V8 in it.Has the Truetrac in the front and the full detroit in the rear.It has a LOT of traction.But onroad it is seamless to drive,you wouldn't know they were in there.

[300bhp/ton]

Ayahuasca said:

Ta, makes perfect sense now.

Do you know if it is possible to retro-fit an axle diff lock?

Usually yes, but it might not be cheap, could break stuff and end up getting you more stuck.

What sort of off roading do you plan on doing, and what limitations have you found so far?

[Ayahuasca]

300bhp/ton said:

Ayahuasca said:

Ta, makes perfect sense now.

Do you know if it is possible to retro-fit an axle diff lock?

Usually yes, but it might not be cheap, could break stuff and end up getting you more stuck.

What sort of off roading do you plan on doing, and what limitations have you found so far?

I understand a rear diff lock is fitted as standard on some Prados (not mine, sadly).
Noit
Type of off-roading - muddy tracks and river crossings mainly. Not an everyday event and not balls-out up to the axles in mud either. I reckon if I had had a rear diff lock last weekend I wouldn't have got stuck in the river. I was perplexed as to why all four wheels weren't turning on a 4WD (I undertand that bit now).

[Della]

The Prado has a limited slip rear diff as standard. Wouldn't this transfer torque to the rear wheel with the most traction?
I'm guessing the front is just a standard open diff for better road driving.

[Ayahuasca]

Della said:

The Prado has a limited slip rear diff as standard. Wouldn't this transfer torque to the rear wheel with the most traction?
I'm guessing the front is just a standard open diff for better road driving.

Mmmm, not sure. I might jack up one of the rear wheels and see if the other wheel turns.

Just realised why this would be stupid. Doh.

Edited by Ayahuasca on Saturday 1st May 18:36

[Hooli]

Della said:

The Prado has a limited slip rear diff as standard. Wouldn't this transfer torque to the rear wheel with the most traction?
I'm guessing the front is just a standard open diff for better road driving.

Limited slips can wear out or be killed with the wrong oil. jack up both rear wheels & turn one. If the other side turns in the same direction (probably at a different speed) then it has a working lsd.

[normalbloke]

Hooli said:

Della said:

The Prado has a limited slip rear diff as standard. Wouldn't this transfer torque to the rear wheel with the most traction?
I'm guessing the front is just a standard open diff for better road driving.

Limited slips can wear out or be killed with the wrong oil. jack up both rear wheels & turn one. If the other side turns in the same direction (probably at a different speed) then it has a working lsd.

That will indicate that it will have one fitted,but that won't really tell you if a plate type LSD is worn or not until you can put a significant resistive torque on the opposing wheel and "measure" it against the figure that the discs are supposed to sip at.Original equipment plate type LSDs in 4x4s are pretty lame mostly.I would not rely on one to get you out of anything significant,and (unless it is new) I would assume it is going to be pretty worn out.

[Hooli]

normalbloke said:

Hooli said:

Della said:

The Prado has a limited slip rear diff as standard. Wouldn't this transfer torque to the rear wheel with the most traction?
I'm guessing the front is just a standard open diff for better road driving.

Limited slips can wear out or be killed with the wrong oil. jack up both rear wheels & turn one. If the other side turns in the same direction (probably at a different speed) then it has a working lsd.

That will indicate that it will have one fitted,but that won't really tell you if a plate type LSD is worn or not until you can put a significant resistive torque on the opposing wheel and "measure" it against the figure that the discs are supposed to sip at.Original equipment plate type LSDs in 4x4s are pretty lame mostly.I would not rely on one to get you out of anything significant,and (unless it is new) I would assume it is going to be pretty worn out.

I must admit the only experience I've got of LSDs was a back axle off a XR4x4 fitted to a XR4i. So not 4x4 type useage.