Monster Truck Madness #3 – Lock & Load
Whether you have a Clod or shaft truck, differential preference seems to be the super important subject that no one really talks about. It’s just not as sexy as discussing, say, brushless options or what tires to use. Locked, open, one axle locked and the other open, limited slip…so many choices!
Before getting into the r/c discussion, let’s talk about how it’s done on the full size trucks. Many of the top freestylers that you see on the Monster Jam circuit are running both axles completely locked. This means that there is never any “unloading” of the diffs and all tires spin evenly. While you may think this would be hard to control, it actually keeps the truck consistent and allows the driver the “pull it back down” when the situation gets hairy. A monster truck also has the benefit of using 4 wheel steer to negate the typical poor turning radius associated with this type of setup on other vehicles.
It also allows for some completely insane saves where the truck is able to keep forward momentum even when the door is practically scraping the ground. The fantastic picture above, shot and provided by my friend Danny Maass, showcases Ryan Anderson in Sonuva Digger demonstrating this effect. Locking just one axle, either front or rear, is also fairly common to allow for similar gravity-bending antics, albeit to a lesser degree.
This load-out isn’t so great when it comes to an r/c monster though. Unlike the big boys, these things don’t weigh 5 tons and therefore can flip super easy when power is constant to all 4 wheels. I find it makes the vehicle handle like a dump truck. Some guys do like it, but from those I’ve personally known who compete this way….they all eventually change to something else.
There are two popular differential configurations- open (like most r/c vehicles) or locking the rear. I can’t stand driving a truck with a solid rear but I know others that wouldn’t have it any other way. The locked rear allows for over-steer handling characteristics and a skilled driver can swing around a turn super fast by having a good throttle hand. The downside is that in high traction situations it’s very easy to go ass-over-tea-kettle thanks to the rear end continually pushing hard.
My preferred setup on all my shaft trucks is to keep both differentials filled with 10k oil to allow for limited slip. The truck still turns great in a bind, but the diffs need at least a little bit of friction to break loose. This means that you get a little bit of the best of both worlds.
Whether you intend to race or bash your solid axle monster, I recommend taking some time and experimenting with different differential settings. These things are strange beasts and you may be shocked to find out what you wind up liking!