Pajero Owners Club of South Africa

Gents
I was asked to go and recover a Fortuner(4x2) from thick sand near Tatasberg camp in the Richtersveld. I was camped at Richtersberg. When I got there it was dug in well and properly. The diff as well as the sparewheel was solidly planted and no grip on the drive wheels, when drive was engaded the wheels turned freely. It was early-ish in the morning and I didn't feel like digging and stuff like that. I just reversed into the thick sand area and hooked up the Furtuner with a tow strap. I opted for 4HLc and de-activated the stability control. (For clarity sake, let me explain that I selected that option well in advance and traveled like that for a km or so)
I pushed very lightly on the accelerator and could see my right rear wheel slowly spinning, while the right front was stationary. I have no idea what was happening on the left side. I was about to abandon the attempt (fear of digging myself in) when the front wheel started turning in a "jerking" way. I turned the steering slightely and the front seemed to turn a bit more. At about that time it started to feel as if the wheels were digging down onto something more resistant than lose sand. I think that was the traction control starting to bite intermittantly and just about then the whole shebang statred to move forward and next thing the Fortuner was free. After this episode I started to wonder if the centre difflock engages correctly.
A week or so later I went up a steep dune at Hondeklipbaai with tyre pressure at a "normal" 2bar - same gear selection as when the Fortuner was recovered. I was amased when we got to the top with no problem and once again, I could feel the T/C biting at the wheels.
My questions are (keeping in mind that I have no idea what was happening with the left wheels):
Do you guys think that the centre diff locked correctly?
Was it the viscous couple in the centre diff that started the front wheel to rotate?
Would I have made the recovery and the steep dune with an open centre diff?

If it wasn't for the fact that the car achieved more than what I could reasonably expect, I would have been more concerned. My final feeling on the matter is that the car did what was asked, but in a way that appears less than perfect.
Thanks
Roelf

Roelf, there is no reason in your anecdote to assume that your center diff did not lock. The center diff lock forces the front and rear propshafts to rotate at the same speed when it is locked. There are however still the two open axle diffs on your vehicle, so the locked center diff will only ensure that one wheel on each axle has to rotate. In your case, the left front wheel would probably have been spinning in unison with the right rear that you could see. Having diagonally opposed wheels spinning is normal in this scenario on terrain that is not totally smooth and even.

With the center diff locked, the viscous coupler does not come into play at all, but if it were active (in 4H) it would not act in a jerky fashion, but rather smoothly.

The traction control system started doing its job when the spinning wheels rotated fast enough to generate positive wheel speed signals for the traction control ECU to do its thing. This is what started the right front wheel rotating in a jerky fashion and what increased traction to the point that the job could be done.

If you want to check out the locking of the center diff with a simple test, proceed as follows:
* Chock the vehicle's wheels so that they can't roll and release the park brake
* Place the transfer case in 4H and the transmission in neutral. Keep the engine running
* Jack up any one wheel and try to rotate it. It should be possible to rotate it, but there should be some resistance due to the viscous coupling on the center diff. The faster one attempts to rotate the wheel, the more the resistance
* Now lock the center diff (the orange indicator must light up and must not flash) and try to rotate the wheel again. It should be impossible to rotate after a small amount of drivetrain play has been taken up.

Gerrit,
Thank you.

The fact that a tough job was done perfectly did make me feel better. Now I can fully relax.

Cheers
Roelf

Thanx Gerrit

Now i to understand how it all works

C'mon PajeroMan,
That is like saying to your wife that you now understand how her head works.. It is all black magic!