what happens if you select 4x4 when the hubs are not locked ?
do the frount wheels get any power or not
ive read every thread i can find and no mention of this anywhere
thanks
- (#7125) andz, 7 Dec 03 19:55
hi
noticed today i have some diesel leaking under the engine but only seems to be when the engine is cold
ie the choke is on
not sure where its leaking from
does not seem to be any of the pipes
anyone had this ?
- (#7125) andz, 7 Dec 03 20:09
If the hubs are not locked in the front wheels get no power.
You won't damage anything by doing it (unless you are going over 60kph - may do something then?????) but you won't get any benefit either - will use more fuel!
Leaking diesel when cold can mean the seals in the fuel pump are on thier way out. It means a service of the pump - Is it also hard to start first up in the morning?
Check around the fuel pump and it should be obvious where it is leaking from.
Dave.
- (#7125) DaveW, 7 Dec 03 20:29
ill get it to the garage
starts up fine every morning
def not the pipes so i guess it must be the pump
thanks
- (#7125) andz, 8 Dec 03 04:30
I'm sure someone will enlighten me if I'm wrong, but I had thought that when the 4wd is engaged, power is transmitted to the front wheels. As there is a differential on the front axle, both front wheels can turn at different speeds. This is good on roads, because going round corners results in the inside wheel turning slower than the outside wheel. This is not good though when in 4 wheel drive in slippery conditions. If one front wheel hits a slippery bit, it spins and reduces the drive to the other wheel. The lockable hubs are used to prevent the front wheels from turning independently, so if one of them hits a slippery bit, the other one still has drive.
Regards
dave Bright
- (#7125) dave Bright, 8 Dec 03 07:03
The locking devices are inside each hub. They lock the wheel to the end of the half-shaft. Without 4WD selected and both of them locked no drive reaches either front wheel.
With 4WD selected and neither hub locked there is no drive to the front. The front propshaft will spin at the same speed as the rear one (no diff in the transfer box in the middle of the car) and the front half shafts will spin at approximately the same speed as the front wheels, but delivering no drive because the wheels aren't locked to them. No harm done.
With 4WD selected and just one front hub locked the front propshaft will still spin at the same speed as the rear one, the locked front half shaft will spin at the same speed as its wheel but, because there is a front diff the other front halfshaft will spin idly (still at about the same speed as its wheel) so that there is still no drive delivered to either front wheel. No harm done.
With 4WD off and both front hubs locked the front half shafts, the front diff and front prop shaft will all spin normally, driven by the front wheels, but there will be no drive connection to the front prop shaft at the transfer box. No harm done.
With 4WD off and just one front hub locked the result will depend on where the most friction is around the front diff. The result may still be that everything spins at nromal speed, or that the front prop shaft stops and the front diff works overtime spinning the unlocked front half shaft backwards - though under no-load conditions so very likely still doing no harm.
Where harm IS done is in selecting 4WD, with both front hubs locked, on hard surfaces with no slip. Whilst the two diffs allow for different wheel rotational speeds on each axle during cornering, the transfer box in the middle of the car cannot allow for even a slight difference of average wheel rotational speeds between the front and rear even when driving straight - e.g. because of different tyre outside diameters - which is absorbed by slippage when on loose surfaces. At best your tyres will therefore stretch and jump around, at worst something in your transmission will give way as the front and rear propshafts, whilst rotating normally, will be driving one diff/axle (the one with slightly larger average wheel diameter) extra hard and retarding the other diff/axle.
- (#7125) Dave (Sussex), 8 Dec 03 08:10
Hi,
I tried the 4x4 out at the weekend (much to the wifes disgust).
I pressed the button on the dash and the icon on the dash lit.
it done nothing on slipery mud.
I then lent out and engaged both hubs and it got me out of the mud.
I then turned the 4wd button off but the icon stayed lit until I had disengaged the hubs.
anyone know why?
- (#7125) spence, 17 Dec 03 18:41
Drivetrain was bound up. Often you can force the light to go out by "modulating" the throttle- go from load to overrun a couple of times, or even stopping and selecting reverse for a mo.
- (#7125) david miller, 18 Dec 03 02:43
What a brilliant site this is. Came on to post exactly the same question, and the answer is there waiting for me already. Thanks, Dave.
I have fitted a new g/box, and the 4x4 selection is now vacuum where before it was all lever. I am about to attempt 700 miles from NW Scotland to SE England, and want to have 4x4 available. Colin-the-garage has (by dismantling the servo) put the beast into 4x4 and then blocked the stub of vacuum pipe to stop the selector popping out. My front hubs are unlocked. I will now perform a 1500 mile road test to see if it does any harm (apart from lowering my MPG, that is). The weather forcast gives me hope that I will get to try the grip in the snow!
- (#7125) Tom, 20 Dec 03 17:46