Operation of 4wd

[Stallion]

Good Evening to all from Dar Es Salaam - Tanzania, Mud Dog, hope all well at your end.

Above is the subject that i need some clarification, only during the dry season.

During the dry season, when going off roading, especially to the Farm, it's not at all necessary to engage 4wd on the dirt road, as the road is full of traction. However during the wet season, it becomes contrary. Now during the dry season, the Hilux is all the time on 2wd, meaning the front prop and differential are stagnant, hence the pinion, ring, spider and side gears in the stated differential don't move. In the transfer case, the 4h and 4l gears do rotate, but aren't engaged. Therefore, during this dry season when one wants to just lube and make sure the 4wd is in a good working condition, how long can you lock the hubs and engage the 4h and 4l without causing winding up of the transfer or the front prop shaft?

I understand that in the wet season, the windup is compensated with wheel slip and wheel lift, that prevents winding up, hence during the dry season at my end, at the farm, the dirt road has full traction, hence no requirement of engaging 4wd. Therefore if you could kindly advise as to how long can you engage 4wd during the dry season on dirt road, just to lube the parts and make sure that the 4wd is in good operational condition.

Looking forward to your responses on this by return

Kind regards
Shermohamed

[Mud Dog]

Hi again. That's easy .... just lock the hubs but not engage the x-fer box for a short trip. Alternatively leave the hubs unlocked and just engage the X-fer box (4H) when the vehicle is stationary, like at a stop or traffic lights. It's the easier option and something I do on a regular basis. Either way is effective and you don't have to worry about any wind up and possible resultant damage. A short hop from one stop to the next is probably good enough. Remember to engage and disengage only when the vehicle is stationary if you have manually locking hubs. (If the hubs are locked you can slip in and out of 4H / 2H on the fly but should only be done on forgiving surfaces.)

It's a simple practice and could be regarded as common sense, but that doesn't mean yours is a trivial question. Quite the opposite in fact. Many novices to 4x4 and indeed some veterans don't know why it should be done. Yes, there's the a notion that it keeps the seals oiled so that they don't become hard and brittle or cracked and there is a little truth to that but mostly the oil does lap up against the seals with normal driving anyway. More importantly IMO is to churn up the diff, and here's the reasoning behind it.

The oil in the banjo housing of an SFA or just the diff of an IFS is considerably less than ½ the full internal volume, in fact it's closer to just one third. The remaining volume is air and that air breaths through the breather as the diff warms and cools, both through use or just fluctuating ambient temperatures. It stands to reason that a small amount of moisture is carried with the air movement into the housing which builds up a little and permeates the diff. If the diff remains static or stagnant as you put it, for any long period of non use, the oil drains off the surfaces that are not submerged or not getting coated with oil slopping about. The oil is not very viscous, so even slopping doesn't reach the upper surfaces and in time as oil drains away, moisture condensation makes direct metal contact which can lead to fine rust pitting of the metal. Not a good thing when it come to the highly polished surfaces on the teeth of the crown wheel and a spider gear or two that are not getting coated with oil.

[Stallion]

Hi Mud Dog,

Thank you for your response on this. I still have some doubts when you say;

1. Lock the hubs without engaging the Transfer Box: This way, the drive will be reversed, meaning, by default, the drive is transferred from the Transfer Box (either with 4h or 4l), to the output shaft of the front prop, that drives the pinion gear into the diff, that drives the ring gear, that drives the spiders, that drives the side gears, that drives the drive shaft to the wheels, that drive the hubs when locked, now when just locking the hubs, the drive will be in the reverse order, meaning the drive will begin from the locked hubs to the drive shaft, to the side gears, to the spiders, to the ring gear to the pinion gear to the prop shaft, and to the output of the transfer case, with that, wouldn't the hubs be loaded with tension?

2. Engage Transfer Case without Locking the Hubs: This will just make sure the engagement into and out of 4wd is working, as the gears are lubed when on normal 2wd driving, as the gears are connected with the Main Box. So this practise will just confirm the engagement of 4wd is in order, correct?

The rest of the paragraph is crystal clear on the SFA & IFS oiling mechanism.

Waiting to hear from you on the above by return.

Regards
Shermohamed

[Mud Dog]

In options 1 & 2 there is almost no strain on the components since all you're doing is activating the drive train without any resistance. Each option does the same thing, just activating it from different ends. There is absolutely no possibility of doing any damage.

Option 1 is in fact what you would be doing normally in situations where you expect that you may need 4x4 traction in some places along your trip ...... I'm not talking about a 100km trip where you expect to need 4x4 in a section of a few metres - in such a case you would logically only lock our hubs when getting to the bad section. However, even if you forgot to unlock your hubs after using 4x4 and drove around like that for a couple of months, the only damage you will be doing is a little extra to your fuel consumption.

For the purpose of "churning" the diff oil as outlined above, in reality you only need to drive a very short distance with the drive train being activated, and like I said, from one stop to the next (which may only be as little as 30 metres) is enough.

Just to be clear on the x-fer box, only the through shaft is engaged in 2H but most of it is submerged in oil and the rest that isn't, gets splash lubricated any way.

[Stallion]

Afternoon Mud Dog,

Thank you for your response on the clarifications on lubing the front drive train on manual hub locks. It's now clear. I guess once I reach the Farm off road section, I'll just lock the hubs and drive in and out of the rough terrain, and will then just engage 4wd in the transfer case for around 300 meters or so and then go on with just the hubs locked, till I get back to Tarmac and then disengage the hubs.

How does that sound?

Regards
Shermohamed

[Mud Dog]

Overkill. ...... It'll do the trick for sure. I just engage the x-fer box for a very short distance without hubs locked once a month (or two months) if I haven't been off-road. Just do it when you think of it.