1997 Jeep Wrangler TJ - Transfer Case Upgrade

Project Teal-J II, Intro
Project Teal-J II, Part 1
Project Teal-J II, Part 2
Project Teal-J II, Part 3
Project Teal-J II, Part 4
Project Teal-J II, Part 5
Project Teal-J II, Part 6
Project Teal-J II, Part 7
Project Teal-J II, Part 8
Project Teal-J II, Part 9
Project Teal-J II, Part 10
Project Teal-J II, Part 11
Project Teal-J II, Part 12
Project Teal-J II, Part 13
Project Teal-J II, Part 14

After reviving the thrashed interior of our TJ in our last installment, we pondered what our next move for our old friend would be. It didn't take long for an answer to arrive. To get an idea of how the Teal-J works in its current form, we took it out to a Southern California area called Truck Haven to do some 'wheeling. After playing in high range for a while, we found a nice ledge to try to climb, which definitely required low range.

A first attempt was made to crawl the obstacle but the TJ would not go. We applied a bit of throttle to bump the Jeep up and over. This maneuver was promptly met with a loud bang, followed by some unearthly grinding noises and a bit of rude language. Looking underneath the Teal-J revealed no carnage, but as soon as we tried to move, the banging and clanging noises continued. We were barely able to limp back to camp, where our NV231 T-case decided it no longer wanted to be a part of the Teal-J and quit completely. We had our answer. A new transfer case would be next.

What we needed, while we were at it, was a set of crawler gears and a tailshaft kit. However, for a bit more coin, we could upgrade from our stock transfer case to an Atlas II from Advance Adapters. Having run an Atlas II in our '69 Bronco test mule for the last three years with no problems, we knew that the Atlas had some serious advantages over the NV231. First, an Atlas is gear-driven, meaning there is no chain to stretch or break.

The T6 aluminum housing is also one-piece and extremely beefy, meaning we don't have to worry about breakage. Another advantage is that low-range ratios of 3.0:1, 3.8:1, or 4.3:1 are available, so there is no need for crawler gears in the axles. Other pluses were that it is quieter than using a gear-reduction planetary set, and it offers a twin-stick setup, which allows you to disengage an axle for easier turning. The Atlas II is also shift-on-the-fly, a feature that can come in handy.

So our decision to upgrade to an Atlas II was easy. We selected the 4.3:1 low-range ratio for maximum crawlability. Once we got our mitts on our new Atlas II, we headed over to the pros at Off Road Unlimited in Burbank, California to tackle the install. While not overly complex, the install does take 6 to 8 hours in a shop, and does require some cutting, welding and fabrication work, so be prepared for that.

The work is well worth it, however. Our Teal-J now has a super-stout transfer case that offers the ability to tackle nasty sections of the trail at a snail's pace. The peace of mind that the strength of the Atlas II offers, along with its crawling ability, is well worth the extra expense and work involved in its installation. Follow along as we show what was involved in sliding the Atlas II into our TJ.

The first step in installing the Atlas II is to remove the stock NV231 transfer case. After removing the driveshafts, the skidplate/crossmember assembly is unbolted. This is the rear mount for the transmission and transfer case, so make sure they are supported before removing it.
The first step in installing the Atlas II is to remove the stock NV231 transfer case. Afte
Next to come off is the transfer case/transmission mount. Make sure not to lose this piece. You'll need it later.
Next to come off is the transfer case/transmission mount. Make sure not to lose this piece
Before the stock transfer case can be yanked, remove all the little odds and ends that are attached to it. This includes the shifter linkage, the four-wheel-drive indicator sensor, the vent tube and the speedometer gear (seen here).
Before the stock transfer case can be yanked, remove all the little odds and ends that are

With everything detached from the transfer case, the nuts holding it to the transmission can be removed. With those out of the way, the T-case can then be taken out.

In this side-by-side shot of the Atlas II and our NV231, you can see that the Atlas is a bit bigger overall. However the rear output is actually slightly shorter on the Atlas than our NV231 equipped with a short-shaft conversion. This means you might need a longer rear driveshaft, which isn't a bad thing, since TJs have short rear driveshafts already. Compared to an NV231 without a short-shaft conversion kit, the Atlas allows for a 6-inch longer rear driveshaft, which is a major gain. If you look closely, you can also see that the front output on the Atlas is farther forward, which means that if you opt for this conversion, you will have to get your Jeep's front driveshaft shortened.

We also made sure to get the stronger 32-spline front output shaft on our Atlas. It is larger, stronger and will accept beefier yoke assemblies than the 26-spline output shaft that is standard. Advance Adapters can also perform the necessary surgery if you already have an Atlas with a 26-spline output and want to upgrade it to the stouter 32-spline unit.

The next step was to put the Atlas into position and to try to figure out its clocking. Once we had it lined up in the position we wanted, the case was marked so we knew which one of the four holes to put the studs in.
The next step was to put the Atlas into position and to try to figure out its clocking. On
With the Atlas back out, the mounting studs were inserted according to the markings that were made. Here you can see the different threaded holes for the studs that allow you to clock, or index, the Atlas.
With the Atlas back out, the mounting studs were inserted according to the markings that w
Next, we prepped the Atlas to be installed into the TJ. The Atlas uses this tube to help you tell where the fluid level is. The fittings for it come loosened. First we applied some Teflon tape, and then tightened them.
Next, we prepped the Atlas to be installed into the TJ. The Atlas uses this tube to help y

The factory four-wheel-drive indicator-light sensor is removed from the stock transfer case and screwed into place on the Atlas.
The factory four-wheel-drive indicator-light sensor is removed from the stock transfer cas
Advance Adapters suggests assembling the shifters on the Atlas before you install it to get an idea of how they go together and to make adjustments. This was a good idea, as once the transfer case is in place, access to the shifter assembly is a lot more difficult.
Advance Adapters suggests assembling the shifters on the Atlas before you install it to ge
Once the shifters are taken back off the Atlas, it can be slid into place under the TJ. We decided to leave it clocked in the same position as the NV231.
Once the shifters are taken back off the Atlas, it can be slid into place under the TJ. We

When we installed the skidplate/crossmember combo we found that the Atlas smacked the crossmember. We didn't want to lose valuable clearance by using spacers on the crossmember, or by notching it, so we decided to take the Atlas back out and re-index it one position higher. Once this was accomplished, it fit with no problem. However, our TJ has a 1-inch body lift, so if yours doesn't, some banging on the floor with a hammer for clearance might be required.
When we installed the skidplate/crossmember combo we found that the Atlas smacked the cros
The next step is to modify the factory tranny/transfer-case mount, which needs the back half of it trimmed off. Off Road Unlimited busted out the torch to make quick work of the cut.
The next step is to modify the factory tranny/transfer-case mount, which needs the back ha
Next to be modified is the crossmember/skidplate assembly. The modified tranny/transfer-case mount moves forward on the skidplate to a flat surface. To match the angle of the original mounting location, the crossmember needs to undergo some minor surgery.
Next to be modified is the crossmember/skidplate assembly. The modified tranny/transfer-ca

Once the crossmember was cut, we could pry up on the metal to match the angle of the original mounting pad, seen on the left in this photo.
Once the crossmember was cut, we could pry up on the metal to match the angle of the origi
The cut section of the crossmember was then boxed and plated for strength and the welder was fired up to fuse the new metal to the old. This is the only mount for the transmission and transfer case, so care needs to be taken to ensure that it is plenty strong.
The cut section of the crossmember was then boxed and plated for strength and the welder w
With both the crossmember and the mount modified, the skidplate could be installed. All that was left to do was drill a hole in the skidplate so that we could access the Atlas' drain plug.
With both the crossmember and the mount modified, the skidplate could be installed. All th

Moving to the inside of the TJ, we removed our console and installed the shifters. Once installed, we shifted them forward and back to check for clearance. A minimum of 1/2 inch is recommended to keep the body from knocking the shifters, and we had to do some cutting of the floor to achieve that.
Moving to the inside of the TJ, we removed our console and installed the shifters. Once in
In the first installment of the TJ project, we installed a Tuffy center console. Now we had to do a bit of trimming on it so that it would clear the shifters.
In the first installment of the TJ project, we installed a Tuffy center console. Now we ha
A finished shot of the install shows how the twin-stick shifters come out of the original location for a factory look.
A finished shot of the install shows how the twin-stick shifters come out of the original