Chances are your vintage military or civilian Power Wagon has the stock 5.83 ring and pinion gears. This ratio was chosen for tactical vehicles to best suit their primary offroad function, and was generally carried over to post war civilian Power Wagons. Chrysler did offer a 4.89 option on some Power Wagons, but few were ordered due to their heavy work requirements. Today, for the majority of trucks driven primarily on paved roads, the stock gearing is inadequate and destructive. The 5.83 gears with 900-16 tires yield 43 MPH at 2500 RPM, the healthy maximum for the Chrysler flathead. Sustained operation above that, particularly at the light to moderate load imposed by the tall gearing, leads to premature bearing failure in the long stroke flathead. The high drive train speed directly affects the model 200 transfer case since 2WD power is transmitted through the transfer gears, generating excessive heat, noise, and wear.
For stock powered trucks, 4.89 gearing is the ratio of choice in most geographic/areas. Yow Dodge will drive nicely at 52 MPH, a 20% increase at the same engine and drive train speed. You will experience smoother, quieter, and more efficient operation since the engine is operating in its peak power range and the drive train is more proportionally loaded. It may be necessary to start occasionally in first, and shift more frequently on hills, but you're going 20% faster in every gear. For repowered trucks, a 4.30 ratio gear set is now available. This will provide a 59 MPH road speed at the same 2500 RPM, and certainly more at the engine's greater speed range. Unlike the greater risk of axle breakage using larger tires, the new gearing
Veteran Vehicles offers a complete rebuild service of Third Members for WC and M37 series trucks, as well as Power Wagons thru WM300. They are fitted with new gear sets manufactured by a respected US gear company. The stock differential is completely rebuilt with new bronze thrust washers and new components as required. A Lock Right or ARB posi-lock differential can be installed when desired. New bearings are installed as needed with pre-loads and gear set backlash set to spec. A new seal and fine ground seal surface on the drive flange assures leak free performance. A final gear shop run-in checks tooth pattern, runout, and bearing free roll.