Atlas II Transfer Case Install / Review
Written By Jesse Weifenbach - 2008

I think most of us have drooled over the thought of owning an Atlas transfer case at one point in time or another. For me the breaking point came on the verge of my first trip to Moab in the spring of 2007. My truck is a manual shift and while there are many advantages to the manual, slow speed control in the rocks is not one of them.It was time to remedy that...

I figured if you're going big, you better go all-out.I order my Atlas II with a 6:1 low range ratio. This is as deep as you can go in the 2-speed model. (Note: 4-speed models are not yet available for Ranger base vehicles.) This would give me a crawl ratio of 93:1 vs. my stock 38:1. As an added bonus 6:1 and 5:1 models automatically receive the upgraded 32-spline front output. Other things you need to specify when ordering are front and rear yoke configurations, right or left side drop, input shaft configuration, and clocking offset.

For those not familiar with the Atlas's features, here are a few:

• Heat treated aluminum alloy housing
• Helical cut all gear drive
• Fully synchronized twin stick shifters
• Heavy-Duty 32-spline outputs
• Ultra-low low range gearing options
• Legendary reputation

The Install:

With all Atlas transfer cases; there is some initial bench setup that needs to be done with the shifters. It was not very difficult due to well written instructions.Next came the fun part.I removed both drive shafts, speedo cable, shift motor wiring and finally the old transfer case itself.You can easily see the size difference between the two transfer cases sitting side by side. Atlas's are designed to handle big block horsepower and torque, so my little 4.0 V6 should not be a problem.

With the old transfer case removed, it was a good time to remove the seats and pull up the carpet in the cab of the truck. If you happen to own an M5OD 5-speed transmission like I do, it is also a good time to check on the shift rail plugs. Over time they tend to dry up and shrink causing leakage from the top of the transmission.Mine were a little weepy, so I went ahead and re-sealed them.

Now came the most critical part of the install, test fitting. I would STRONGLY suggest using a good transmission jack to lift the Atlas into place. There are several reasons for this. One, the Atlas is HEAVY.Dry weight is 110 lbs.There was no way my skinny girl arms could lift that thing into place and hold it steady. Second, a transmission jack allows you to tilt the whole assembly which comes in handy when trying to line up the dowel pins by yourself.Lastly, you want the Atlas to be steady and perfectly lined up when you slide it onto the transmission output shaft or you risk damaging it. Before you lift the transfer case into place, you need to be aware that you will probably have an interference problem with the body of the truck. Advance Adapters recommends that you install a small body lift to gain the necessary clearance. Your other option, and in my opinion the better one, is to replace the stock cross member. I was fortunate, I already was using a SkyJacker Class II cross member that lowers the transmission mount slightly. This fixed the interference problem for the most part. I was able to get the Atlas into place on the first try, but I noticed it was close to the body near the rear shift rail assembly. I pulled the transfer case down and gave the body a few "whacks" with my small sledge hammer. This fixed the problem very easily.

After fixing the body interference issue, I put the Atlas back into place and grabbed the supplied transmission to transfer case mounting bolts. Immediately I had another problem. 4 of the 5 bolts went in fine, but the fifth one was too long and would not clear transmission mount to slide into its hole. Rather then unbolt the transmission mount, I ground the bolt down slightly so it would “make the turn” into the hole. I slowly and gently tighten down the bolts. This turned out to be a good idea as I ran into my next problem. As you can see from the picture, the Atlas did not seat all the way against the tailshaft housing:

After an hour or two and removing and reinstalling the Atlas several times carefully measuring shaft clearances each time, I discovered the problem. If you look carefully, you can see where the transfer case and the tailshaft housing were contacting each other.


The problem was an easy fix once I knew what is was.I got out my Dremel Tool and carefully removed a little material and was on my way.

With the Atlas securely in place, it was time to cut the hole for the shifters. Advanced Adaptors was nice enough to supply me with all the shifter links pre-cut for a Ranger/Explorer/Bronco II setup, so after some quick work with a jig saw, the shifters were in place. The next item to be installed was the custom speedometer cable adaptor. This unit was ordered ahead of time from Nevada Speedometer. You will also have to purchase a Jeep speedometer gear and housing because this is the style the Atlas uses. These parts can be purchased through a Jeep dealer or at a salvage yard. The instructions include a chart to help you pick out the correct gear for your tire and axle gearing combination. Total, these additional parts will set you back around $150-$250.

Final Steps:

Now that the Atlas is installed, you will need to measure for new driveshafts. I was lucky.My rear shaft had enough slip yoke to make up for the extra length needed and I was able to shorten the front one myself. You will also need to build a new skid plate under the Atlas, as it hangs down lower then the stock Borg-Warner case. For me, this would have to wait for another day because I would also be installing a new long arm suspension and it would require a completely new skid plate as well.

Final Thoughts:

During the initial test drive, the Atlas was very noisy and it had a lot of shifter vibration. This was a little disappointing. Over time I figured out that the vibration was caused by the engine. Nothing was wrong, the engine is just not as smooth as a Mercedes and the shifters are very rigid and transfer all vibrations. I see this as a design flaw. You will notice that on a factory manual shift transfer case there is a rubber bushing to soak up drive-train vibrations. Eventually I removed the shifters and reworked their mount with homemade rubber bushings instead of the supplied hard plastic bushings. This also solved the noise problem because there was a little play in the plastic bushings that caused a noise going down the road. Otherwise the Atlas has performed exactly as expected.The 6:1 low range has been very useful on the trail and allowed me to try some more technical lines.The one downside to super-low gearing is lack of wheel speed in the dunes. This was expected and doesn't bother me since I spend most of my time on the rocks. These could be fixed with more horsepower. Another option would be to build a Borg-Warner doubler.This is generally cheaper then the Atlas and gives you more gearing options, but will likely require major gas tank, cross member and driveshaft modifications. I would encourage people looking for lower gearing to check out both options. I chose the Atlas because I wanted a bullet-proof setup and so far, I am very happy with that choice.

Disclaimer: This article is intended to describe my experience installing an Atlas transfer case in my truck and is in no way a step-by-step guide for this type of installation. All modifications to your truck are at your own risk. It is advisable that if you do not fully understand all aspects of a given modification that you consult a professional for help.