is it 4x4 or AWD?

[dgsmooth]

howdy - i have a 99 scrambler 400, was just reading the owners manual online and its talking about on-demand 4x4? is that how it works? how does it know if the rear wheels have lost traction? i'd be bummed to find out it does work like that.... if thats the case i'll be re-wiring this so it works like my 96 scrambler did - push the button and 4x4, guess that was too simple. anybody with some advice on this would be greatly appreciated..... thanks and ciao for now.

[pathfinder]

Yours probably works the same as the newer models, which is "on demand". So, when the handle bar switch is in 4x4 if the rear wheels slip two lugs then it will engage the front wheels. You can basically drive all the time with the switch in 4x4, but unless the rear wheels slip you are actually in 2 wheel drive. Hopes this makes some sense.

[dgsmooth]

yeah that part makes sense, thanks buddy, but what i'm wondering is how does the machine know the rear wheels have slipped? where is it picking up the rear wheel speed? from in the tranny somewhere? the front coils have 4 wires through each, so i'm guesing one pair is for the actual coil and the other for some type of 'speed sensor', then it somehow compares that to the back end speed and if they dis-agree then the rear wheels are slipping etc, but looking through the wiring schematic i can't see any type of rear speed sensor..... if i knew how it was picking up the rear speed then i would bypass or modify that end so it 'thought the rear wheels were always spinning', and thereby keep it in 4x4, the way my '96 did.... anybody know how this thing knows the rear wheel's speed/spinning?

[blueline15]

its not speed sensors, its mechanical. when you are in 4x4 mode, the coils are primed but not engaged. They are in what is called override mode. The machine is basically "pushing" the front end, because the front end is geared in 4x4 to spin at 20% less speed then the rears. So as long as that happens, the fronts stay disengaged but in the "override mode." As the rears lose traction, and start to spin, the fronts will engage and pull the machine along, while the rears continue to push. As the rears regain the traction and start to over run the front wheel speed, they go back into their disengaged "override mode". The entire engagement and disengagement is mechanical, except for the electricity from the switch that energizes a coil to "prep" the front drive for pulling. Its more complicated then this, but thats the basics.

You can essentially trick the machine into thinking the back end is always loosing traction, by installing rear wheels that are 20% smaller in overall diameter then the fronts. Then you will always have the front wheels locked in.

The problem with doing this is that it will be very difficult to steer, you will wear out your tires, and other front end components like balljoints much faster.

[dgsmooth]

wow - what in the world was wrong with the old system? so you said the front spins 20% slower than the rear, meaning the drivetrain spins 20% slower than the front wheels, or the wheels spin slower than the drivetrain. i think i'm visualizing it - the drivetrain spins slower than the wheels until the drivetrain (or rear wheels) break free and then the drivetrain is able to speed up to the same speed as the front wheels and as it tries to spin faster than the front wheels the one-way clutch in the hub grabs the front wheel and then front wheels are driving... so if a put 20% larger front wheels that'd be the same thing also?

i'm hearing you about the premature wear, but i really only use 4x4 in really bad situation. i/we mostly ride trails and climb sand hills etc where its usually higher speed, but sometimes if we're crossing a river or huge muskeg hole, i'd like to engage 4x4, then crawl through the bad spot, then dis-enage and go, like i used to do on my '96 scrambler. is there maybe a way to change or modify the clutch in the hub so it won't spin freely in either direction? is that the only difference between the old stlye and the new on-demand style is the wheels gearing and hub clutches? thanks again mates and cheers.....

[blueline15]

dgsmooth, sounds like you do understand the basics of the on demand system. I will look into it a little more, because I am not as sharp on the older years as I am the newer ones. I cant remember when the swap in style came, and the actual specific mechanics of the system. But I can certainly get you the tiny details so you understand the differences. But....

I am traveling across the country tomorrow morning, so my time will be limited. I will try to get you a more exact and very specific answer as soon as I can, even with some diagrams if you can be patient enough with me as I move across the country.

I'll try to be as quick as possible.

[dgsmooth]

hey of course buddy, thanks for the help. just a little interesting info i found, for a 99 (cb) scrambler 400, the front clutch assembly part number is 1520281. if a look up a 96 scrambler, it shows the same number as the 'new' number, but says it replaces part number 1520214..... i wonder if that -14 number is a full locking clutch and the new number is a one-way clutch. if i could mess with the rear sprockets and the tire sizes and get the road-speed on front and rear the same (or nearly), i'd much rather have old-style full locking hubs. thanks again mate and ciao for now.

[camppowersports]

The old style hubs like on your old scrambler work the exact same way your new ones do. All polaris 4x4s have always been "on demand"