B. Atlas T/C - History, Updates to the Atlas over the Years & FAQ

Advance Adapter's History of the Atlas Transfer Case

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.

Phases of design and development

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).

Current production models


The Atlas was first released in 1995. Over the years we have made improvements, design changes, and expanded the vehicle applications. The Atlas holds a strong reputation as the ultimate upgrade for an off-road vehicle. We have continually strived to improve on the Atlas where we perceived any short coming or potential weaknesses and have always tried to evolve on the overall performance the case provides the end user. The dates or serial numbers listed below are significant changes in the Atlas and could affect the replacement parts needed if you are rebuilding or ordering parts for an Atlas transfer case.

1/1/2006: Cast iron forks.

5/4/2006: Site tube change, was ½" pipe fitting and is now a ¼" fitting.

11/30/2007: Changeover to 32 spline input gear on all ratios. All number from here on started with a "G". (The Atlas 6.0: gear set was also discontinued at this time).

9/3/2009: Heavy duty 32 & 29 input shafts introduced, 300M material.

1/1/2010: Serialization of cases on the mill (6-digit serial numbers) - 9600.

5/27/2010: "SF" Gear sets introduced for the off-road racers.

7/22/2010: Changed breather location and venting design on the main case - 10143.

8/19/2010: Increased tap depth of pan mounting threads from .45 to .75 min depth on case and went to longer Atlas pan bolts - 10289.

9/10/2010: Changed from 5/16-.75" B.H.C.S. to 5/16"-1" B.H.C.S. on the pan bolts - 10500.

11/23/2010: Changed from 5/16-1" B.H.C.S. to 5/16"-1" F.H.C.S. (flange head cap screw Grade 5) to aid in assembly - 10550.

In 2010 we dropped the "G" on the serial numbers and machined serials into the case, 6 digits.

2/2011-3/2011: The second-generation Atlas 4 speed was released.

12/16/2011: The Atlas front retainer for the 32-spline front output was updated to a one-piece housing.

2/25/2011: Added spot face feature to rear bearing cap and changed bolts to 5/16"-1" F.H.C.S. - 10875.

3/15/2011: Added "Advance Adapters" to the engraving on the main case 10910.

1/24/2012: Removed pockets from cluster pin bore so that cluster pin could be lengthened - 12314 (old pin P/N 300122, new P/N 300122A).

3/9/2012: Changed 300384 casting to allow for all 1.25 mounting bolts - 12299.

3/2012-4/2012: All Atlas' shipped with solid synchro dogs vs. the sheet metal ones.

4/24/2012: Cable shifter connections at the transfer case are easier to install and allows removal without disassembly of the shifter box. (Less chance to break a cable /installation error).

5/10/2012: 1. The shift rails became bio-directional or the same rails are used for left and right shifter controls. 2. The location of the Pollak switch was moved to the bottom of the shift block and the thread size was changed. 3. The shifter indexing to the case was changed over to dowel pin and the brass bushing in the case were removed. Note the current shifter will still work on early cases with the brass indexing.

10/2/2012: Atlas 4 speed planetary has been revised to allow all inputs to fit into one housing.

10/18/12: Atlas 3.0 Gears are now all full fillet design. These gears should not be mixed with gears that were not full fillet (This design adds up to a 20% strength upgrade).

1/1/2013: Atlas 3.8 Gears are now all full fillet design. These gears should not be mixed with gears that were not full fillet (This design adds up to a 20% strength upgrade).

10/2013: cast rear bearing cap replaced with new billet aluminum cap.

12/2013 The Atlas started to use a bolt on retainer for the front input bearing in the race applications, replacing the snap ring P/N 716456 In January 2016: We updated all cases to the bolt on bearing retainer.

12/19/13: Started shipping heavy duty case with case saver part number 300360

6/5/13: Removed rubber seal washer from under yoke nut, silicone should be used when changing the yoke.

1/17/14: Started shipping 1.5 gear sets

January 2014. Change over to a 5" index on the input as well as 8 bolts fastening the housing to the case. The earlier inputs were a 4.56" index into the case and used 6 bolts.

10/2014 I.D> tags were added to the rear of the main case

10/2014 The case breather was moved to the shifter block.

3/1/14: New 300499 & 300500 Dual Lip Seal used

4/29/14: Started shipping new Atlas 2.11 gear ratio

6/18/14: Started shipping Atlas 2 Speeds with universal case part number 301100A

12/4/14: Started shipping Atlas 4 speeds with universal case part number 301100-HD

In 2016 a new serial number referring to the manufacturing date was used. Current serial numbers are 7 digits (first digit is last number of the year, next two are the week that the case was machined and the last four are a numerical sequence. We start every year with 0001.)

10/2016 introduced the larger idler pin 1.500".

6/2017 new rear cap was designed for the HD case as well as the 4-speed case, this new cap has the addition of fins on the casing to aid in cooling and offers better oiling for the bearings P/N300105A

7/2017 The front output housing was updated to a casing with fins for cooling and improved oiling for the bearing's P/N 300103A

2018- prototype flat tow units were shipped out and production parts are ready to start shipping 10/2018.

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.