The Original Low-Buck Locker
It's been called the Lincoln Locker for decades, but not because ol' Honest Abe had one in his ride. It's simply 4x slang for the type of machine used to weld your differential's spider gears in place. For all intents and purposes it could be a Hobart, Lincoln, Miller, or "whatever brand of metal-fusing device that you have plugged into the wall of your garage" locker. Now, before we get too far in the low-budget realm of welding your spider gears, we need to look at why one would even do such a thing.
The standard differential carrier in most vehicles is what's known as an open carrier. This is a series of (generally four) spider gears that rotate inside the carrier and are designed to delegate the power to your axleshafts. This design is sufficient for on-road purposes as it allows your tires to spin at different speeds, so when you corner and turn the vehicle there is less difficulty or bind. When you have an open carrier off-road it sends power to the tire with the least resistance, which usually means the tire with the least traction, leaving you a one-wheeled wonder.
By welding your spider gears solid, you have forced the shafts to rotate at the same speed, thereby creating a locker. Functioning similar to a spool, welding your spider gears is extremely hard on your equipment, but is without a doubt the cheapest and easiest locker you will never buy. It is great for off-road-only rigs, as you can have your rig locked up in less than an hour using only a drain pan, a can of brake clean, and a welder. So for all you guys wheeling on a budget, but who need traction now, here are a few steps to help get you on your way.
While people have been welding their spider gears for years, it's definitely something that comes with an inherent element of risk. Though lockers in general put more strain on your drivetrain components, a welded carrier can presumably cause even more internal damage if the welds break and the discarded pieces come between your bearings and ring-and-pinion. Street manners of a welded unit will be that of a spool-very aggressive-and may create strange handling. For our money, welding up your spider gears is a great way to get traction fast, especially if you're on a budget and you or your buddies have a welder handy.