Its got a beefy cast-iron case, an all-gear design, and twin shift rails just like an NP205. But its got a little weenie output shaft just like a Kia Sportage. Well, maybe its not that bad, but compared to the rest of it, the 11/8-inch, 26-spline output shaft has caused way more headaches for hard-core four-wheelers than any other part of the Dana 300 transfer case. Imagine throttling up a steep, off-camber hill only to hear a sickening pop followed by the sound of your rear driveshaft whacking the floorboard of your rig. Youd have about 0.02 second to enjoy it before you needed to hit the brakes to prevent an unwanted reverse and tumble.
Thankfully, for hundreds of hard-core enthusiasts, Advance Adapters has come out with a tailshaft upgrade kit that includes a monstrous 13/8-inch, 32-spline output shaft and aluminum tailhousing that uses a bigger bearing. The kit even includes a 1310 yoke since the yoke for the stock shaft wont fit the larger-diameter Advance piece. Once installed, the new tailshaft kit is ½ inch longer than stock, but that shouldnt be enough to necessitate driveshaft modifications.
We took our parts to MIT in El Cajon, California, where Rick Dziezyk showed us how to replace the weakest part of the Dana 300. Although the installation doesnt require the removal of the intermediate shaft and gear, Dziezyk needed to check the condition of the needle bearings for wear in this particular application. Since the case is out of the vehicle and partially disassembled, nows a good time to diagnose any weird noises that may have been emanating from your case.