The Dana 300 may perhaps hold the most potential for extreme hard-core use of any stock Jeep transfer case. It has all-gear innards, along with a compact case that fits between the stock framerails of early Jeeps. Good cases are readily available in junkyards, or your Jeep may have come with one stock. Add to that the fact that JB Conversions offers the parts and pieces to build your Dana 300 into a trail slayer with upgraded 4:1 gearing and 32-spline front and rear output shafts or as a complete assembled unit delivered to your door for half the price of a similar aluminum aftermarket T-case, it's hard to pass up. Even later-model YJ and TJ guys looking to swap in a passenger-side drop axle would be wise to consider a 300 as a viable alternative to an aluminum T-case.
Follow along as JB Conversions builds a Dana 300 for our '53 flattie. We didn't need to do the 4:1 gears because we run extremely low axle gears and have a granny First gear in the SM420, but we did want the throttle-proof, 32-spline front and rear output shafts and twin-stick capability that our new JB Conversions Ultimate 300 offers. No longer is our use of the throttle limited by our Spicer 18's weenie 10-spline outputs.
To mate our new Dana 300 to our SM420, we ordered a Novak Conversions adapter kit (PN 423). The kit included a new 10-spline input shaft that easily bolted in our new Dana 300. In addition to being made of superb material, the aluminum adapter is a miniscule 3.2-inches long and allows three clocking positions. We were able to use the adapter's existing holes to clock the Dana 300 in the same orientation as our Dana 20/Spicer 18 hybrid (Dana 20 case with Spicer 18 gears and shafts).
Size-wise, the Dana 300 was nearly identical to the Dana 20 case it replaced. We just needed to do a bit of gentle clearancing with a hammer to the floorboard that resulted more from the clocking than the size of the case. After the install, we still have the same amount of room between the framerails and the T-case. In fact, we were able to reuse the custom crossmember we had built for our old T-case. All we needed to do was cut the mounting tabs from the frame and reweld them farther forward.
Comparing our new Ultimate...
Comparing our new Ultimate 300 (right) to a stock Dana 300 is sort of like stacking Janeane Garafalo up against Jennifer Anniston. One's ugly and sort of useless, and the other you'd be proud to mount in your Jeep.
JB Conversions selects only...
JB Conversions selects only the best useable cores for the basis of its Ultimate 300 cases. This is our case after it came out of the blast cabinet where it is stripped to bare steel.
All of JB Conversion's twin-stick...
All of JB Conversion's twin-stick efforts are for naught if we don't have two sticks to put to the case. We ordered up 4Wheel Drive Hardware's Dana 300 twin-stick conversion kit (PN 6450). We had to cut and weld the shift handles to shorten them for use in our flattie, but the linkage worked just as delivered.
The increase in tooth size...
The increase in tooth size can be seen in this comparison between a LoMax gear (left) and a stock Dana 300 gear (right). The large tooth profile means more engagement and less chance of a broken or chipped tooth.
This is the LoMax 4:1 five-gear...
This is the LoMax 4:1 five-gear set produced by JB Converions. Since the stock 2.61:1 ratio gears are a better match for our application, we don't get the benefits of the LoMax gear's increased strength. The LoMax gears are not only made from top-quality materials, but they increase the tooth thickness and size for more contact and strength.
The Dana 300 rear-shaft kit...
The Dana 300 rear-shaft kit comes with bearings, small parts, shaft, and a new heat-treated aluminum housing. The housing is set up with a flange face and dowell pin holes in the event a parking brake needs to be mounted. If not, the billet cap is installed in the mounted kit.
The broken rear output shaft...
The broken rear output shaft is a stock 11/8-inch, 26-spline Dana unit. The 13/8-inch, 32-spine JB Conversions shaft, by comparison, is made of 8620 heat-treated alloy and is crazy strong.
The stock Dana front output...
The stock Dana front output is 26 splines and weak enough to fail in applications with big motors and tires. The 32-spline shaft kit JB Conversions offers comes with a new yoke, output shaft (as shown), and bearings.
JB Conversion's rotation plate...
JB Conversion's rotation plate (left) comes with a variety of available input gears. The retainer in the iron case is one offered for NV4500 conversions. The stock retainer and input gear are shown at the bottom of the photo.
One of the bores in the shift...
One of the bores in the shift tower (left) is deeper than the other. JB Conversions installs a check ball under new stiffer springs so they sit at the same height. This places an equal amount of pressure on the two shift rails, eliminating the tendency for the rear shift lever to jump out of gear when the case is twin-sticked. Lower spring pressure is desired on the inner rail when using the J-linkage intended for a single stick. This lower spring pressure is needed to allow the cam action to work on the single stick linkage plate. JB sells the spring and ball kit individually, as well.
Worn teeth are common to stock...
Worn teeth are common to stock Dana 300 shift slide rings (left). JB sells a slide-ring kit with two new, hardened rings (right) that hold up to abuse without chipping and pitting.