Dana 300 Transfer Case - D3: The Second ComingPosted in How To on July 1, 2008 Comment (0)
STaK 4x4's Dana 300 Replace-A-Case has put the Dana 300 transfer case in the same class as GM's 350 small-block V8, where used donor parts such the 350's block or the 300's housing are no longer required for assembly. With a diminishing amount of usable Dana 300 donor housings available in wrecking yards these days (the Dana 300 hasn't been used in a production vehicle since 1986), the Dana 300 Replace-A-Case effectively extends the life of this stout geardriven transfer case that has dutifully served in multiple makes of 4x4s during its multiple-year span of production.
The Dana 300 Replace-A-Case consists of two case halves that are manufactured from cast 356 alloy aluminum and then hardened to a T6 condition. Each case half offers thick walls to hold up against case deflection under hard acceleration. In order to maintain tight tolerances throughout the assembly, the profiles of the case halves and all bearing locations are fully CNC-machined to exacting specifications. The case halves are joined using 3/8-16 stainless steel socket-head cap screws to ensure positive attachment and further increase the unit's strength.
In addition to bringing more overall strength to the Dana 300, the STaK 4x4 Replace-A-Case is impressively versatile. Its design allows it to be used as a direct replacement for less desirable chaindriven transfer cases such as the NP231 in Jeep YJs and TJs. This is achieved without using the common method of mounting the Dana 300 upside down to turn it into a driver-side drop transfer case. Several clocking positions are already in place on the Replace-A-Case to suit the mounting needs of many applications, and many different input splines are also available. When used to replace an NP231 transfer case in Jeep TJs and YJs, the Dana 300 adds approximately 9-1/2 inches to rear-driveshaft length, which will effectively decrease the operating angle of the rear driveshaft in these short-wheelbase rigs. The Replace-A-Case accommodates the factory TJ and YJ speedometer-sending units, and STaK offers a TJ-style shifter that's designed to fit through the factory hole in the transmission tunnel as well. A universal shifter is available to suit other applications and can be modified as needed to meet most needs. STaK can also provide adapters to mate the Dana 300 to most GM, Ford, and Jeep applications.
As far as building a Dana 300 without a Dana 300? It can be done using the Replace-A-Case and all new heavy-duty aftermarket components like a 32-spline front-output shaft or a 32-spline rear-output shaft that uses a shorter tailhousing manufactured from billet aluminum (STaK offers these too). Also readily available for the Dana 300 are 4:1 Low gearsets as well as bearing rebuild kits. Of course, this isn't your only option. You can also assemble a Dana 300 using the Replace-A-Case and quality used components from an '81-'86 Dana 300 core. This will create a stout transfer-case assembly that can be upgraded over time as needs and funds dictate. Either way you slice it, new parts or old, the STaK 4x4 Replace-A-Case is an awesome upgrade to any Dana 300 transfer case and a great option for those eager to step up to a geardriven transfer case without the cost of purpose-built Low-geared units.
DANA 300 OVERVIEW
The Dana 300 transfer case uses all helically cut gears and a cast-iron case. It benefits from a compact size and its versatility in being able to mate up to a variety of transmissions. Available in '80-'86 Jeep CJ-5s and CJ-7s, two versions of the Dana 300 were produced: a reputedly stronger short version and a long version. The reasoning for the two versions is said to be due to the varying wheelbases of the CJ-5 and CJ-7, with the weak link in the long version found along the mainshaft. Both offer a 2.62:1 Low-gear ratio and use an aluminum tailhousing, a 1-1/4-inch intermediate shaft, and 23-spline input shaft. There's also a Scout Dana 300 that was used in the '80 International Scout II. A few differences exist between the Jeep and Scout models, but most importantly, they do not share the same bolt pattern. The Jeep 300 uses a round six-bolt pattern. The Scout 300 uses a four-bolt "Texas" pattern that is essentially the same pattern as the five-bolt Dana 20, making it an excellent swap candidate for early-CJ owners seeking a lower gear ratio.