This is a message about my previous posting.
OK, let's say that the problem is with the speedometer or one of the switches.There has to be a way to bypass the bad switch. I would like to have a the 4x4 stay engaged until I decide to disengage it with a switch.Not by this auto stuff.Is there some way to wire the hubs straight to a switch without shorting any thing?

 

I have a 99' 400 scrambler with the same problem. Here is what I did:
1. Check to see if the switch is working. Jack up the entire 4 wheeler. While you are giving it gas in gear, push the 4x4 switch and see if your front drive shafts are engaging. If they dont ...i would guess its your switch. But if they do engage, but the wheels dont...the problem is in your hubs.
2. Drain the hub oil (it was black and really really dirty) then refill with new "hub oil" I had to buy the $4 a bottle polaris stuff, but that beat new hubs. That fixed it for me.

 

....sorry I forgot to add something. When you fill the hub back up with oil turn the hole to the 4 oclock position, let the excess oil drain. then you are done... If that doesnt help...sorry Man