In late 1995, Advance Adapters, Inc., sought to venture into the ultra low 4WD gear business to satisfy the high demand that 4WD enthusiasts were looking for. With various low gear units out on the market already, we wanted to design a product that was unique - something we felt would command a market of its own. We heard of tooling and some components that were available from the early Ford Courier 4WD conversions. We felt that buying the tooling and the engineering would be a fast start for developing a low gear ratio transfer case.

The tooling was purchased from a gentleman in Ohio. From that point on, we began incorporating new features into the Atlas transfer case. One of the first things to be added were synchronizers to allow "shift on the fly" capability, combined with a new lower ratio by utilizing a full gear set. Included in this new transfer case would be a much needed heavy duty rear output shaft. Based on our acquired tooling, we targeted Wranglers, and early Broncos, which are of the "left hand" drop configuration. As we took into consideration these changes, we soon found that the tooling we purchased would be limiting. We needed a more versatile design allowing us to also include the right hand drop applications (CJ's), as well as early and late model left hand drop applications.

With the original reworked tooling, we had produced 5 prototype units that we shipped out to chosen candidates for testing. Reports back from one prime candidate, who has a well know early Bronco, warranted the demand for a totally new design and tooling. After his first few trails we were not surprised to hear of a broken prototype. We immediately received this unit back for analyzing and found that the gear design was marginal.

To quickly get our candidate back on the trails, we shipped out another prototype unit. In the meantime, we began redesigning the Atlas to withstand the abuse that these units would be subjected to. This meant redesigning the case of the Atlas to accommodate larger gears and eliminating the original reworked tooling. Just about the time we had the Atlas I completed, we were assured of being on the right track when the second prototype failed in the burly Bronco. (He had now cracked two "peanuts"!). Fortunately, we were ready to ship the first totally new Atlas I to rescue the "peanut". Continuing close contacts with our Bronco test pilot, we are pleased to report no failures. Now, he says he is breaking other weak links like Dana 60, 35 spline axles!

With the Atlas I in production, Advance Adapters purchased a prototype vehicle of their own to aid in the further refinement of the Atlas I transfer case. This was a 1989 Jeep YJ with a 6 cylinder and Torqueflite automatic transmission. As we started installing the Atlas I into the vehicle, we realized our next set of challenges to overcome. In trying to produce the Atlas I for a wide range of vehicles, we overlooked the front driveline clearance on this particular vehicle. We lacked about a 1/2" of clearance on the Torqueflite transmission pan and had some problems with the shifter linkage serving this vehicle. To remedy these problems, we opted to retrofit a GM TH350 automatic replacing the Torqueflite to allow the Atlas I to be installed in this vehicle.

Knowing that we had to make provisions for front driveline clearance and shifter linkage, we opted once again to do some fine tuning on the Atlas I. We found that the Jeep automatics were going to be a popular application, so we decided to stretch the case 1" from centerline to add clearance for the front driveline. At the same time, we redesigned the shifter linkage to accept a modular twin stick design for the Atlas consumer. As we stretched the unit, we utilized the added space by enlarging the gears, creating a super strong transfer case.

The Atlas II was then created

With the Atlas II now in production, we were presented with some new applications. The Jeep Wrangler TJ series seemed to be a popular application. We were concerned with the shifting mechanisms fitting into the new TJ consoles, so Advance Adapters purchased a 1998 TJ for prototyping the Atlas II and to obtain the proper shift linkage configuration. This application and installation is previewed in the Jeep TJ Installation section of the Atlas Manual. In 2007 the new Jeep JK was introduced. The Atlas was installed and new shifter linkage was designed to keep the Atlas application current with the current production vehicles.

The Atlas II has proven to answer the gearing requests that the 4WD enthusiast was looking for. Although the unit was originally designed around the Jeeps and early Broncos, now the universal design of Atlas II enables it to fit a wide range of vehicles. Offered are two new super strong ratios of 3.8:1 low range and a 4.3:1 extreme trail ratio.

Since then, numerous upgrades have been incorporated and a wide variety of ratio options have been designed to accommodate any type of drivetrain combination. The Atlas 2 speed ratios include: 1.5, 2.0, 3.0, 3.8, 4.3, & 5.0.

Along with these 6 different ratio options, we are now producing our new 4 speed Atlas Transfer Case. Atlas 4 speed ratios include: (1.0:1 / 2.0:1 / 2.72:1 / 5.44:1) OR (1.0:1 / 2.72:1 / 3.8:1 / 10:34:1).

This unit has under gone a few design changes from its original release. We pulled the 4 speed from the market in June of 2010 and redesigned the planetary housing, shifter and added a mid-plate with a support bearing to handle the higher horsepower engines and larger tires that were being used with the transfer case. These improvements did add some length to the case but also add the needed strength for these vehicles. This new 4 speed was released in January of 2011, and is now offered in 5 ratio options: (1.0:1 / 1.5:1 / 2.72:1 / 4.08:1) or (1.0:1 / 2.0:1 / 2.72:1 / 5.44:1) or (1.0:1 / 2.72:1 / 3.0:1 / 8.16:1) or (1.0:1 / 2.72:1 / 3.8:1 / 10.34:1) or (1.0:1 / 2.72:1 / 4.3:1 / 11.70:1).

Frequently Asked Questions:

Question: Why does my Atlas blow oil out the vent tube/breather?

Answer: Too much fluid will cause foaming at high speeds. Foaming oil expands and fills the entire cavity, which forces fluid out the tube; or the breather hose may be restrictive, causing the Atlas to build up pressure. On late model Jeeps, we have found that you must replace the restrictive breather (located on the firewall) with a free flowing atmospheric vent. This vent is typically found in earlier model vehicles. The stock vent was for lighter viscosity oils such as the ATF.

Question: Why does my Atlas pop out of gear?

Answer: Check for shift lever interference around the floor and dust boot. Make any additional clearance modifications needed. Engine and transmission mount combinations vary in rigidity, allowing some with more movement than others. The "TJ" support is by far the softest we have seen.

Question: How should the unit be flat-towed? And how is the unit oiled?

Answer: For flat-towing recommendations, please refer to the towing subheading in the Operating section of this manual. In reference to lubrication: The Atlas gears are supported on the shaft by a full complement of needle bearings. This design allows for less friction to develop in the unit. As long as the proper oil level is maintained while driving the vehicle, proper lubrication to these bearings is being achieved. In 2018 we now offer a flat tow option for the Atlas that has an oil pump for flat towing.

Question: My Atlas seems to be hard to shift. Why?

Answer: It could be one of two reasons. First, the linkage could be binding. You may need to inspect for possible trouble areas. Refer to the Final Installation section under the subtitle Shifter Problem Checklist for more information. Second, the Atlas has shift rail detents, controlled with a ball and spring set. You can back off the brass set screws located on the shifter boss about a 1/4 turn, allowing an easier shift. As the unit is operated, components will seat in. After the first service, the brass set screws should be tightened 1/4 turn to return them to their original position.

Question: Can I change my Atlas gears to a higher or lower ratio?

Answer: This option is available; however, the parts & labor necessary may not be cost effective. New gears would be required. Items such as bearings, seals, and gaskets would need to be replaced. And shipping and labor costs would also apply. We can quote you on the cost of an upgrade, or the other recommendation we could offer is that you sell your current Atlas and purchase a new one with the desired ratio.