I used diff lock grease in the spider gears on my Cen MT2 and it has caused quite a few problems for me. It stressed the diff cups more than normal. It stressed the axles and dog bones more than normal. and it stressed the diff more than normal. This all resulted in three destoyed dogbones, two destroyed CVDs, three destroyed axles, and more diff cups than I care to mention. And that is just from grease in the diff. Plus it doesn't handle as well, it hops around on pavement during take off, and what little I gained in traction is not worth the cost in parts. I would only lock your diff if you are willing to replace more parts more often than you would otherwise.