2. Atlas Transfer Case - 4 Speed Units

Atlas 4 Speed Transfer Case

Advance Adapters has built upon the proven design of the Atlas 2, to create the revolutionary Atlas 4sp. No other transfer case on the market today has 3 separate low range ratios built into a single unit. This transfer case was designed for the off road enthusiast that likes to tackle a large variety of terrain with one vehicle. Selecting one low range ratio that works well for mud, sand and rock crawling, is a compromise but the Atlas 4sp overcomes this limitation. One transfer case that is perfectly suited to any terrain that you may want to conquer.

The 4SP has essentially two parts. The first is the reduction housing. This housing holds a planetary assembly that has a gear ratio of 2.72:1 when in a low range, and a 1:1 in a high range. It has one shifter coming out of the top to select the desired range. The planetary is not a synchronized shift-on-the-fly design and must be operated when the vehicle is stopped. (The main case still retains the shift-on-the-fly capability just like the standard Atlas). The reduction housing shifter is designed for a cable shifter.

The second part of the 4SP may look the same as the standard Atlas, but it does have some differences. The main case of the 4SP is the same raw casting, but has some machining variations to make it into a 4SP. The main case functions independently from the front reduction housing and retains all of the normal Atlas features (front and rear outputs controlled independently, and the a front only option). All of the gears are the same. The front output uses all of the same parts along with the cluster. The strength of this unit is not an issue. We use a planetary assembly that was originally run in a NP241-HD transfer case. The six planetary gear setup has proven its durability and has been used in countless heavy-duty vehicles. Other attributes to the planetary assembly include a very quiet operation, easy shifting, and low rolling resistance. When all of this is put in front of a legendary Atlas Transfer Case, you get the best combination of gear ratios and reliability.

The 4SP units will fit nearly all applications that the standard Atlas will bolt to. These will include spline counts of 23, 27, 29, 31, 32 and 34. The unit has a circular bolt pattern on the front, identical to the one found in Jeep, Ford & Dodge vehicles. We have a variety of different adapters available to retrofit the 4SP into nearly any application. The twin sticks for the main unit can be either the standard linkage or the cable linkage. The standard linkage is offered in a variety of custom packages available for particular vehicles and can be modified to fit many custom applications. The installation of an Atlas 4 speed should be nearly the same as the standard Atlas 2 speed. The Atlas 4 speed is just a bit longer.

We do not recommend flat towing vehicles equipped with the 4 speed due to the additional bearings used in the planetary housing.

Since every Atlas transfer case is custom built to order, the unit will be customized to your vehicle. Please browse this site or give us a call to determine how to configure the ultimate transfer case, and have us build you one for your vehicle. CASE: Material: 356-T6 Heat Treated Aluminum Weight: 125 lbs. (dry) INTERNAL COMPONENTS: Gears: Helical Cut Planetary Gears: 6 Gears Helical Cut Bearings: Needle & Taper Rollers Synchronizers: Borg Warner Available Input Shaft Splines: 23, 27, 29, 31, 32, 34 Tail Shaft H.D., 32 Spline Front Output 32 Spline


Low Range:1.5:1, 2.72:1, & 4.08:1 or

2.0:1, 2.72:1, & 5.44:1 or

2.72:1, 3.0:1, & 8:16:1 or

2.72:1, 3.8:1, & 10.34:1

2.72, 4.3:1, & 11.69:1

To start your order of a new Atlas 4 speed Click Here

High Range 1:1 LUBRICATION: Quarts: 2.5 Liters: 2.36 We are currently shipping Redline 75W-90 GL4 with all new Atlas units, this along with the other lubricants that are printed in our Atlas Installation Guide are the recommended fluids for the Atlas. LENGTH COMPARISON: *Atlas Short tailhousing is 16.75" *Atlas Long tailhousing is 18.75"

New Process 231 is 20.5"

New Process 241 Rock Trac T/C is 15-1/4"

Dana 300, 12"


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