Buddy openly admitted that the Spartan never unlocked from the day it was installed, and that's exactly how it drove...permanently locked
Then one day on the way to a trail, I pulled out of my favorite fast food drive-through, and B A N G. Well that didn't sound right, but the truck drove fine for the rest of the day, so I assumed the locker had unlocked for the first time in it's life LOL.
Then on the trail I got into some really deep mud and water and the truck got stuck. I'd been through the same hole a few times on previous runs, so I knew the truck should have made it through no problem.
Then buddy radio'd me and said one rear wheel wasn't turning - right then I knew something wasn't right!
It turns out the Spartan had let go earlier on in the day and I didn't notice it, other than the B A N G.
When I got the 3rd member on the bench I saw shims, which was my first red flag...the instructions say not to use the shims..
It seems for a Ford 9" new side gears need to be purchased if the side gear deck height is not tall enough....and they measured too short. So they used the shims to make up the side gear deck height.
So mystery solved.
There had been some installation errors and/or short cuts made when putting the Spartan in, and that's why it never worked correctly.
No big deal, I had a spare differential, so I swapped in the spider gears and put it all back together.
My new dilemma is what to do for a traction aide?
The last 3 locked rear ends have all resulted in some kind of breakage....they were; welded, spool and Spartan (like a spool) - so all 3 were permanently locked.
I might try a limited slip next time so there is some traction help, but not enough to break things.
