I have a friend who is asking me about the Polaris 4WD system. I only know about my "3WD" Honda . What he wants to know is: when you push the button that activates the 4WD system, how does it work. Is it electrical to mechanical to hydraulic, or what? And, once engaged, what happens if you turn around on pavement? Why don't you twist an axle? And, once engaged, do you get exactly a 50/50 split in power to the front and rear axles? Any other comments about it are welcomed.

 

I understand how it works, but I can't explain it very well. If it helps any, in the hubs, it's a big electromagnet that grabs and turns the wheel with the shaft, so it's not actualy meachanicaly "engaging". When it senses the front shafts not trying to spin faster than the wheel, it allows the magnets to release, so it steers just like it's in 2wd. When the switch is off, it just doesn't allow power to go to the magnets.

That's very summerized version, but I hope it makes some sense. I had a basic understanding of how it worked but it wasn't until I ripped one apart and got my hands dirty that I really understood.

There is no differential, both front shafts are turning all the time. It's kind of like the rear end of your Honda, but with u-joints on the axle so it can move up & down. There is no way for only one wheel to spin.

 

The front wheels only pull when the rear wheels have lost traction and they quit pulling when the rear regains traction. There are some wires going to the front hubs so I asume they are engaged electricly. I don't know much about it, but it works good. I'm sure there are some folks around here that can give you a more detailed reply.

davidg

 

It won`t engage if you are running on pavement since you have traction to the rear wheels.

 

Unless you spin the tires on wet pavement.

 

Thanks very much for the quick response and the help. I will print this out and any subsequent posts. He got an explanation from the dealer, but honestly did not understand and was not sure of what the salesman told him or if it was correct. Thanks again.

 

Here's a little more explanation about how 4WD works. The electromagnets in the front wheel hubs engage the 1-way clutch in each front wheel. This connects the wheel hub to the axle as long as the axle is trying to turn faster than the wheel is turning. If the front wheel is turning faster than its axle, the clutch "overruns", i.e. it doesn't conncet the wheel hub to the axle under this condition. Even when you have the 4WD switch closed (engaged), the front wheels will not be propelling the vehicle if the rear wheels are not spinning at least a little bit.

All of this is made to work by designing the gearing between the rear and front axles and the front and rear tire sizes so that the rear tires are always trying to drive the vehicle just a little bit faster than the front wheels are; i.e. on hard ground in 4WD only the rear wheels are driving; the front wheel 1-way clutches are overrunning.

With this design and the gear ratios and tire sizes the vehicle has, the front wheels do not furnish any tractive effort until the rear wheels spin enough to let the front axles try to turn just a little faster than the front wheels are turning. One result of this design is that if all 4 wheels are furishing tractive effort (i.e. propelling the vehicle), the rear wheels will be spinning slightly even if the front ones are not. Another way to illustrate it is that any time all 4 wheels are propelling the vehicle, the rear ones will be turning at a speed that, for example, would drive the vehicle 10 mph and the front ones will be turning at the speed the vehicle is really going, say 9.5 mph.

One question I can't answer is how the Polaris 1-way clutch design enables the front wheels to also provide engine braking by the front wheels in 4WD. I would like to learn how this is accomplished.

For whatever it is worth. Al Elston

 

Al,

Don't try to understand this, they don't. EBS doesn't use the front wheels for braking even when the machine is AWD. There have been several posts in the forum wishing that the fronts would help when going down hill.

Oh, well. You can't have it all.

------------------
Kevin Staton
Y2K Polaris Magnum 325 4x4
<a href="www.korrnet.org/watvclub">Windrock ATV Club</a>

 

One time, when I was on a trail driving on a power line. I needed to turn around. I backed
up and turned off the trail. My atv dropped down into a swamp. I was lower than the trail
and stuck in 2wd. I put my polaris in 4wd. 1st. gear. Instead of the atv just driving up
out of this hole. It jumped up out of the hole. I did not expect that and thus was startled. I dont know how the atv did that, but it was very impressive.

rangerchet polaris xpedition 425cc 5 speed.

 

Now how does this work if you change the sizes of the tires? I have a 2000 SP 335. The front tires is smaller than the rear. If I change the tire size and put the same size on front and rear does it work and if so does it do any damage to the system.

Andy T
Jackson, MS