The reason I ask is because I used the 3pt hitch blade today in some 5/8 minus gravel and without the diff lock (rear) it was spinning b2920...front right and Rear left. No problem once diff. lock engaged but front locker would help that much more!
Sounds like you need more ballast-loaded tires and/or wheel weights on the rear and suitcase wieghts on the front if you don't have a loader. If you have a loader then scoop a bucket of rock for front ballast.
The front axle isn't strong enough to have a locker in it, thats why they include one on the rear only in the little models. If you have no weight on the front it wouldn't help much anyways.