Johnson Valley is home to some of the best rockcrawling trails in California. There are several hammer trails, including Claw Hammer, Jack Hammer, and Sledge Hammer. In July, Brad Kilby of Onboard Air hit Sledge Hammer with his brother, Charles in his TJ-7. It's constant hardcore rockcrawling without much relief anywhere along the way.
Some folks can drive the trail in only an hour.
However, depending on breakage, experience, and size of the group, others may take all day. If you do the trail without any sidewall punctures, you're doing pretty good. Be glad when you don't break anything. Brad says a few guys with limited slips in the front have made it through, but it depends on the driver and the condition of the trail. If you make it out to Sledge Hammer, be sure to check out the mailbox at the end of the trail.