Do these trucks have lockers or some sort of posi trac? Do they need additives? The reason I'm asking is: The other day I locked it in 4hi at a stop light and put it back in 2 further down the road. I went to the mall and parked. When turning right out of the mall parking lot it started jumping and wouldn't harldy turn. I convinced myself it was stuck in 4 because I pused the 2hi button again and it didn't do it the rest of the way home. Then last night (4 days later) I was getting back on the highway, after trading my left leg for some diesel, it did it again. I was turning right. Only this time it seemed to come from the back. It acts like my mud truck with the welded rearend. It felt like it was spinning the right tire and it was wheel-hopping. It doesn't do it all the time but I sure don't like it. Any ideas?