Confirming the 4wd is working

Sorry in advance if this is a stupid question.

I am trying to confirm that the 4wd is working on my new jimny. And also to get it clear in my mind how the mechanics of it all work.

I took it on a wet field and the back wheels were still spinning like mad but could't tell if the fronts were doing any thing (my 1st 4wd)

When I select 4wd the front prop does lock up yet with one front wheel lifted off the floor it spins freely, I have read that it shouldn't spin?

The local motor factors said that i need to have both front wheels in the air and they should spin togeather? I suspected the front diff might not be working but he also said that it would be banging its nuts off if it was knackered.

Can anyone help out.

Thanks

In 2WD, only the rear axle drives.
In 4WD three things happen:

1) the front hubs lock with a "CLICK", they are air operated, and will only work with the ignition on, and possibly the engine running (there is a small reservoir though under the wing)

2) the front propshaft locks to the rear one. This forces the front and rear axles to turn together, and is a GOOD THING on mud, as the drive is split 50%, making the wheels less likely to spin.
This is a VERY BAD THING on tarmac, as the front and rear axles need to go at different speeds around corners, so the tyres scrub, (if you are lucky) and the CV joints break.

3) 4WD low activates an epicyclic reduction gear as well, to reduce the wheel speed, and provide more torque at the wheels, for steep slopes, and deep mud.

To test,

Engine running, engage 4WD, the hubs should click. Handbrake on, jack up one front wheel, and try to turn it by hand. It should only turn a few degrees each way. If it goes round and round, most likely the hubs didn't lock.

Engine running, engage 2WD, the hubs should click again. Handbrake on, jack up one front wheel, and try to turn it by hand. It should go round and round.



Don't use 4WD on tarmac, and be careful in the wet, a Jimny will spin round and round very easily.

Enjoy

Thanks for the information, with the engine running and one wheel of the ground the wheels go round and round, so thats why I thought that the diff might be knackered.

Next question how do you check the hub operation

I removed the black centre of the wheel (6or8bolts) which looks like it locks the wheel and drive shaft together. After a bit of probing it seems to jump into place so guessing the operation is working, I will try and find the vacum hoses and work back over.

If the vacuum system is leaking, the 4WD light flashes to tell you the hubs couldn't lock. (Not didn't, it can't tell, it only measures the vacuum when the hubs are activated)

There is a big section on checking the control system in the manual, check the usual suspects for a download.

If the light is steady, then likely there is a blocked pipe, or someone swapped the pipes over

The light is a steady green, so i'll check the pipes for blockages.

I just started thinking the worst, and cursing the bloke I bought it off. Hopefully it will be something simple

Cheers, I have downloaded the link so will work through that, if I get no where i will swap to manual hubs.

Cheers for your input

Mark

I was thinking that it should be possible to modify the vacuum hubs to manual, just needs a button on the outside to knock in to lock, and pull out to unlock, the magnets hold everything in place.

that write up is very good, thanks to who ever took the time out to create it. I haven't had a chance to look at the Jimny yet but at least I know where to look now

Yes I agree this is an excellent guide, I thought I knew how the hubs worked but I had no idea about the vacuum tank and thought they only worked with the enging running.
The only query I have is with the "checking the system" guide 16.
Item c and e if the wheel turns then you can only say that either one or both of the hubs have not locked you can't say which one. At that point repeating fot the other wheel is pointless. If it's the one that's off the ground then obviously the wheel will turn, But that hub could be locked OK, the halfshaft would turn and counter rotate the other halfshaft in the diff if the other hub has not locked. Admittedly in the second case rotating the wheel might have more resistance but it might be difficult to tell.
Please feel free to point out the error of my ways if you think I'm wrong!
All in all I think this system is far superior to the many varieties of "automatic" FWH over the years, Frontera and Maverick spring to mind! and I think if mine failed I'd be tempted to fix them rather than replace them and this guide would certainly help.