Drive to the Front Wheels

[JohnFromPerth]

When 2wd is selected in the Sport, do the front wheels continue to drive the front diff and driveshaft to the transfer box? Or is there automatic hubs or a disconnect in the front diff to save fuel and tyre wear when running in 2wd?
I have previously owned a Jackaroo that had an electric actuator in the front diff that disconnected the half shafts to the front wheels when in 2wd. Also a BL series Kia Sorento that did the same thing but used compressed air like an air locker.
Earlier 4x4s of course had manual locking hubs that disconnected the front wheels.

[Phree_ed]

My understanding is that the front drive shaft is decoupled from the transfer case and that's it. The front hubs remain engaged and backdrive the front diff and front drive shaft.
This means that unlike free wheeling hubs which disconnect the front wheels from the drive system so that nothing is being driven and fuel is saved due to less friction the Mitsubishi system saves next to nothing.
But then it has to be like this because 4H can be selected at any speed up to 100kph. If the front wheels were disconnected from the hubs then the front diff and drive shaft would not be turning and engaging 4H at any speed would result in some serious and expensive noises as the drive system was made to instantly accelerate from 0 to whatever rpm was necessary to match the road speed.
As it is though the front wheels backdrive the system so it's already turning at road speed and nothing has to change as the front drive shaft is reconnected to the transfer case and drive is established to the front wheels.
The only thing that can upset it is if you are turning when 4H is selected because then there will be a speed difference between front and rear wheels and this is why the handbook says to be going straight ahead and not turning when engaging and disengaging 4H.
Hope this helps.

[woffleon]

It has free wheel electric hubs. Select 2H start the engine and you can turn the front shaft by hand. While your down there grease the universals! You can turn the shaft to orient the grease nipples but not the rear shaft.
Stop the engine and the hubs will lock. The moment you select 4H it will engage the hubs and sync with the transfer case engagement (and subsequent marriage)

If it itches it will be scratched!

[OldPS]

In manual has hydraulic free wheeling , basically it disconnect/connects one side halve shaft , so with no drive to one side , when in 2wd , there is no drive to front wheels , but all components ie hubs , halve shafts , front diff , front tail shaft etc are still turning , just no drive .

[NFT5]

Interesting how different people interpret the system.

In older models, up to about 2014 (?) there was a disconnect at the transfer case and another in the short shaft on the right hand side of the front diff. This one in the front, which was vacuum actuated to get 2WD, i.e. 4WD default, tended to cause a few problems so eventually Mitsubishi scrapped it.

Later MN Tritons and Challengers have the new system, as does the Pajero Sport and MQ Triton. The real Pajero has, certainly up to NW, the old system still.

There's a little more energy used with the new system, but not much.

[OldPS]

Especially the transfer box . My previous car was a LR that I found easier to follow , with neutral ,high and low gears and a normal looking diff in the transfer box ie no chain and easy to see how the centre diff was locked , and no 2wd option . I would also preferred the LR option of low range without centre diff locked as one option , great for slowly manoeuvring heavy van etc in difficult situations , although that was a manual and the ps auto does help . Did pre2014 have both disconnect at transfer case and front diff ? Cheers john .

[NFT5]

Yes. Vacuum with the engine running disengaged the default 4WD mode. It was a great system when it worked but vacuum hoses could leak and the switch was very exposed so easy to damage and then expensive to replace. Half the reason for bash plates was to protect this setup. Dozens of threads about flashing green lights.

The new system may use a cup or two more fuel per 100km but it's much simpler and obviously less prone to damage.

I had a Disco, too. Loved the low range availability without CDL.

[nj swb]

In manual has hydraulic free wheeling , basically it disconnect/connects one side halve shaft , so with no drive to one side , when in 2wd , there is no drive to front wheels , but all components ie hubs , halve shafts , front diff , front tail shaft etc are still turning , just no drive .

OK, reading this thread I'm confused about who's discussing the new system (of which I know little), and who's discussing the old.

With the old system (still current in Pajero), disengaging the r/h actuator in 2wd means the front left wheel drives the side gears, which drives the r/h output shaft in reverse - because this is easier than driving the crownwheel, pinion and front drive shaft. Lose vacuum on 2wd and the disconnect attempts to engage two shafts spinning in opposite directions, which makes the sort of noise you would expect.

The transfer case mechanism that engages the front shaft while moving includes a synchro mechanism - I have a pair of brass synchro rings at home waiting to be installed in a Gen 4 transfer case.

[insect_eater]

I think I've stripped a gear tyring to visualize this. Are there diagrams somewhere?

Nailing this clearly once and for all would be a great resource thread for both new and old systems.

[JohnFromPerth]

I have taken a good look around under the front of the vehicle and at the front hubs and there is no sign of any free wheeling hubs, disengaging diff or any other system to free wheel the front drive when in 2wd. It looks like the old 1960's-70's Landrover/Jeep/Landcruiser setup where in 2wd the front drive shaft is disengaged in the transfer box and that is it.
If you run in 2wd the front wheels push around the front diff and front driveshaft.

Looking at page 6-28 in the owner's manual, it states that 4H full time 4wd is the basic position for the Super select 4wd II system. This gives drive to all four wheels with the center diff in the transfer box unlocked to prevent transmission wind-up.

I will be leaving the transmission in 4H for on road running as Mitsubishi recommend.

Cheers
John

[NFT5]

I think I've stripped a gear tyring to visualize this. Are there diagrams somewhere?

Nailing this clearly once and for all would be a great resource thread for both new and old systems.

The online manual has reasonable diagrams of the system with the actuator but none without. I guess that if it doesn't have it then those components are simply not there. Inside the drive shaft is just longer.

I have taken a good look around under the front of the vehicle and at the front hubs and there is no sign of any free wheeling hubs, disengaging diff or any other system to free wheel the front drive when in 2wd.

Correct. As I said above the later models don't have the actuator. I said 2014 but it was actually earlier than that, 2012.

[OldPS]

Ok , had a look at my dec2015 PS , it has a vacuum operated actuator on the drivers side of the front diff , so unless mm changed the system after mine , I would assume all PS have this system to disengage front drive when 2wd is selected .

[JohnFromPerth]

I think you are right OldPS.

I asked the mechanic at my MM dealership when I took the vehicle for its 1500km check. He says that there is a vacuum actuator in the front diff that drops off the drive to the front half shafts so allowing the front wheels to run free of the drag of the front diff and front tail shaft. The vacuum comes from the camshaft driven vacuum pump that provides vacuum to the power brake booster.

The next question he did not know the answer to.
What is the default position of the actuator? That is, is vacuum applied for 2wd, or for 4wd, and , more importantly, if there is damage to vacuum line to the front diff causing loss of vacuum, does it leave you in 2wd or 4wd.
This could be important in getting out of a difficult situation off road.

I note the comment by Woffleon on page 1 of this thread when he says that the front tail shaft is free with the engine running with 2wd selected, but locks when the engine stops. This suggests that with no vacuum the system defaults to 4wd. This is good as it means the default position with a vacuum failure is 4wd.

A further thought is if there is damage to the vacuum line to the front diff, does it compromise the power assistance to the brakes?

[pharb]

Interesting how different people interpret the system.

In older models, up to about 2014 (?) there was a disconnect at the transfer case and another in the short shaft on the right hand side of the front diff. This one in the front, which was vacuum actuated to get 2WD, i.e. 4WD default, tended to cause a few problems so eventually Mitsubishi scrapped it.

Later MN Tritons and Challengers have the new system, as does the Pajero Sport and MQ Triton. The real Pajero has, certainly up to NW, the old system still.

There's a little more energy used with the new system, but not much.

What is this new system?

This might explain why, when the young fella bought a 2nd hand MN front diff for his ML (only one he could find with correct ratio), it didn't have the driveshaft actuator system in the RHS extension housing.