"Detroit Gearless Locker 3" is what your looking for. I had one in my 1998 Grizzly 600.
There was 4 models produced, which covered about 90% of the full time 4wd ATV's on the market at the time. You need the #3 locker for the Grizzly 600. Most Yamaha's took the #3 locker. The Wolverine 350 took the #1 if I remember correctly.
And good luck finding one. They have been discontinued for well over 10 years. Even rebuilt kits were discontinued. I had trouble finding one in 2008. Took me over a year then. Around 2012 I tried rebuilding one for a friend of mine (the clutches were wore out), and was told no rebuild kits were available and they were no longer producing them.
Because of a lack of rebuild kits, most are worn out at this point and are no longer fixable. The Detroit Gearless Lockers needed to be rebuilt every 2-5 years, depending on use and maintenance. Rebuilt even more often with lack of maintenance or swamping the diffs full of water and mud.
Every oil change required friction modifier additive to be added as well. If you didn't put in the friction modifier additive, the locker wouldn't work and the clutches would fail/wear even faster. Friction modifier additive is available at most auto parts stores, or your local Ford or GM dealer.
I hope this information helps in some way. I hate sounding like I am bursting your bubble about this, but it's better than you possibly buying a used one, only to find out it needs to be rebuilt and you can't do it. You'll have wasted your money buying a paper weight.
Not sure how deep you are wanting to tear into it but have you considered swapping a 660 diff in? Dezz did you ever look into this to see if it was possible? I'm sure if it was easy you would've done it though. If you could get the diff swapped in, we have an electric diff lock conversion kit that runs standalone off just two wires, power and ground so the electrical part would be easily covered. May be more work than it's worth, just a thought. We have considered trying to make a locker conversion kit for the older 600's but have not experimented with it too much just yet.
I never tried swapping in a different diff. It was too much time and money at the time to complete.
But it would be possible. You would need custom axles and custom front driveshaft before the electrical even touched.
A 660, 450, or 350 diff could be the donor diff as it's the same amount of work to make any one of them work.
Thanks for the info guys. I know its a long shot but I thought it wouldn't hurt to try. I wonder if the clutches in the locker would work from other models? It would seem to be in Detroit's best interest as far as tooling and cost of production, to use the same clutches in several models and just machine the housings, splines, etc for the specific quad. Just a thought.
I have considered doing a 660 diff swap and looked into it a little bit. I actually regret not doing it when I had it stripped down to the bare frame as it would have been a prime time while the frame was being reinforced and powder coated.