Okay, so i got a diff from an 08 Big Bear 660 and tried putting the 3B4 actuator / servo onto 2016 kodiak diff, it bolted right up but the diff does not have a locker. just had to confirm. Also it cost me a lot more than $20.. as i bought the diff, the wiring harness, the switch, the cdi, relays.. everything. Cost me $240. All i needed though is the diff with the 3B4 and the connector plug and enough wiring to reach the top. could've saved $100 by not buying the CDI. (guess i'll try to sell it on ebay and make some money back.)
The other diff had a ujoint yoke on it, i removed that and put on the yoke from the kodiak.. all bolted together nicely. shafts fit perfect and all.
next came wiring, I contemplated all the wiring and relays and cdi etc but it was too much of a mess to figure out. even with a service manual and wiring schematic it would be a nightmare to get it all working with the big bear selector switch and everything involved. I found that all I needed was the 2 far left pins from the servo. 12v and ground connected one way it spins one way, reverse the wires and it spins the other way.
To get the 12v and ground I spliced into the adapter where my winch plugs in instead of splicing into factory wiring. then i got a double pole double throw toggle switch from radio shack, it resets back to center when released.
https://www.radioshack.com/products/20a-dpdt-momentary-flip-switch?variant=5717529733
12v on one side, ground on other side, then run 2 wires from diff to the switch on one end of switch.. splice another set onto the same wires and flip them and put on other side of switch. mount switch somewhere. works like a champ in/out of 2wd/4wd and can lock it. just a matter of holding the switch. here's a pic of how to do the switch.
Diff lock works.. much harder to steer in diff lock, but i love it already. did some 4wd diff lock donuts just trying it out. wish I had power steering now... still very happy with result. I will get power steering on this next. watch and see.
I hope this has been somewhat understandable and I hope this helps someone like me that wants diff lock for cheap.
https://www.radioshack.com/products/20a-dpdt-momentary-flip-switch?variant=5717529733