David 4:1 Klune-V - Extreme Underdriving

So How Does It Work?
We've had the David (4:1) Klune-V extreme underdrive in our giant fullsize Cherokee for a couple months now. We've taken multi-hour roadtrips to trailheads, and had it in some precarious positions in some nasty off-road spots where wheel speed control was ultra important.

We may be using the word "control" too much throughout this story, but that is the one word that comes to mind after using a Klune-V in our ride. Almost all the gear slop seemed to go away (there is a lot with 47-inch tires on the ends of the axles) when in low-low, and we didn't have to feather or throttle the accelerator when overcoming obstacles. A nice steady forward motion was a welcomed addition to our off-roading adventures.

As for the drivability on pavement, it didn't have a single effect. There was no extra gear slop, and no extra noise from an extra gearbox being installed in the drivetrain.

Final Gear Ratios
With the 4:1 Klune-V David extreme underdrive and 2.6:1 Dana 300 low range, we have four different gearing ratios available between the transmission and driveshafts.

Will Gear Reduction Increase Breakage?
We were curious about this ourselves, as we've definitely experienced more breakage in trucks when putting more power under the hood. Wouldn't adding lower gearing increase torque, and therefore lead to a higher potential for drivetrain breakage? We asked Greg Miller of High-Impact Transmission and Gear his opinion on the subject, and he got back to us with this answer:

"It has been my experience that you break less, not more, when you gear way down. First of all, you can never develop more torque on a component than what the tires will make traction for. And in most cases, you can already make enough torque to break all four tires loose with a standard low range if you punch the throttle hard enough.

"Secondly, leaping, thrashing, and making and breaking traction puts surge loads on parts when you're trying to hurry over an obstacle (due to lack of throttle control). This does not happen when you are geared down and controlling a slow ascent or descent."