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"Advanced Adapters Atlas II"
4.3:1 Transfer Case

Installation and review
By: Rick Horwitz

Ever since I grenaded my stock transfer case back in '96 I was looking forward to a heavy duty replacement for the BW 13-54. The 13-54 is a light weight chain driven unit which does fine in all, but the most extreme off-road environments. 

One day while browsing the 4x4NOW website I saw that Mike Partridge, General Manager of Advance Adapters was going to be available on the "Ask the Expert" forum. I used this opportunity to ask Mike if he had plans for the highly renowned Advance Adapters, Atlas II transfer case to be available for our Ford Explorers. I told Mike about this website and about all of the people who were very serious about making their Explorers off-road worthy. Mike told me he would research the market to see if there was interest. 

Fast forward to the 1999 SEMA show in Las Vegas, Nevada. I met Mike in person at the Advance Adapters booth. I introduced myself and gave Mike my card. He remembered me from our online discussion and told me that the Atlas II was being built for the Ford Explorer, I was super happy to hear this great news. Upon returning from the SEMA show I announced the availability of the Atlas II.. It wasn't very long before Paul Bredehoft, one of the regulars on this website, bought the first Explorer based unit. A 3.8:1 unit which is optimal for an automatic equipped Explorer.

The Atlas II is available in two configurations. "Ultra-low" 3.8:1 and "Extreme-low" 4.3:1. The 3.8:1 ratio is recommended for those with automatic transmissions as the 4.3:1 is so low the stock brakes would not be able to hold the Explorer back at an idle. With a manual transmission this is not a concern because you can simply disengage the clutch and come to a complete stop. For full technical details check out this page: Atlas II.

Installation Procedure: For '93 Explorer w/ manual transmission

1. Given the height of my truck (5.5" lift) there was no need to put the truck on jack stands. First I placed a floor jack under the transmission. Next I pulled the drive shafts, transmission cross member, stock shift lever, speedometer cable and the wiring from the stock transfer case. At this point I supported the transfer case with another floor jack and removed the 5 bolts holding it in place. Once the bolts were removed I worked the transfer case free from the transmission adapter. I lowered the transfer case with the floor jack and slid it out from under the truck.

2. I setup the shifters on the Atlas II out of the chassis as the Advance Adapters manual suggests. This is to get the basic adjustment down and to get a feel for the way the assembly fits together. Once I had the shifters set up (10 minutes), I broke down the assembly except for the long threaded rod, and the gold shifter ends.

3. I used my 2-1/2 ton hydraulic jack to raise the Atlas II close to its mounting point. Care needed to be taken to feed the shift rail (long threaded rod) up and over the transmission adapter. I needed to leave clearance between the top of the transfer case and the floor. That's because the transfer case was being lifted in perfectly flat and once the splines were engaged and the case was mated with the adapter the case needed to be rotated for the bolt holes to line up. It required a bit of wrestling to get the splines mated, but it went together pretty easily. 

4. I have the second Atlas II ever to be sold for an Explorer. Paul Bredehoft has the first. Both of our transfer cases were shipped with the wrong studs, they shipped studs with SAE threads instead of  Metric which is what's needed. The original bolts from the 13-54 are slightly too long to thread fully into the Atlas II. I needed to get some new bolts or studs. Note: I have spoke to Mike Partridge and he is aware of the situation. He is now shipping the unit without studs and recommends that the original bolts be cut. My personal recommendation is to buy shorter bolts. My local Ace Hardware had metric bolts which were about 1/4 - 5/16" shorter. These fit perfect and it saves from having to cut and use a die to clean up the threads on the stock bolts. While you're waiting for your Atlas II to arrive from the factory you could pull an easy to reach bolt and use it to find a slightly shorter set at a hardware store.

Custom cross member

5. Reinstall the cross member and transmission mount.My transmission cross member was custom built after my troubles at the Truckhaven pre-run. The new cross member lowered the transmission quite a bit. This worked out great with the Atlas II. I bolted everything up and there is plenty of clearance all around the T-Case even though it's  larger than the stock unit. You will find that you will either need to modify your cross member, build a new one, or use a 1" body lift to gain sufficient clearance between the new transfer case and the floor board.

Notch was made for shifter access

View from opposite side

6. The stock Explorer uses a CV on it's front drive shaft. The Atlas II didn't come equipped with a CV yoke on the front so a new drive shaft was made to the correct length (in this case 29"). My drive shaft shop, Dick's Drive shaft in Phoenix, assured me that the single U-joint setup would allow more flex than the CV type, so that's what I used. The rear yoke on the Atlas II is a CV type yoke. Once again the CV is not needed so the rear drive shaft was cut to the correct length and fitted with a 1310 slip yoke made for extra articulation. A 1310 strap kit was used to hold the front U-joint in place. The standard 1310 strap is a tight fit in the CV yoke. I told Mike about this and he told me that he has a supplier for special straps which are made specifically for this situation. Mike is sending me the new straps and he plans to include them in future kits. All of my U-joints are now "Brute Force". The drive shafts were installed at this point.

Shifter rods as seen from the bottom

Finished interior, nice and clean!

7. While the T-Case was still in place I used my friends Sawzall to notch the drive shaft tunnel for shifter clearance. The shifter handles which they included were pre-bent for the Explorer. They would have worked fine with an automatic transmission, but the shifter for the rear axle was making contact with my 5 speed shifter handle. The fix was easy enough, I just bent the rod with a long pipe to create additional clearance. I completed the installation of the shifter linkages per the instruction manual and was ready to button up the installation.

8. The final details included patching the drive shaft tunnel with a piece of sheet metal. I cut the metal to size and used sheet metal screws to hold it in place. Black silicone was used to prevent rattles and to keep heat out. I installed the shifter boot which was included with the Atlas II. Next I had to remove the original transfer case shifter boot from the stock assembly and cut the left side and the bottom from the stock trim piece. I then fed the 5 speed shifter boot over the handle and the Atlas II dual stick boot now protrudes from where the stock shifter used to go.

The optional fluid level site kit is shown here

I have been off-road with the Atlas II a several times now. All I can say is WOW. Actually I can say more.  There's a hill close to my house which has lots of whoop-dee-doos all the way up. It stretches the suspension pretty well as one tire goes into a hole and the other gets picked up by a berm. Anyway I dropped it into low range at the bottom of the hill and placed the transmission in first gear. I let out the clutch and let the truck IDLE all the way to the top! The RPM's barely rose to over 500 yet the progress of the Explorer never slowed. 

This deep of a low range isn't for everyone. You give up speed on the trail (at least in low range, high range remains the same) for extreme torque and throttle control. The manual transmission is much easier to control on obstacles with the deep low range. Rock crawling has become a pleasure instead of a chore. Let the clutch out slowly in lowrange and get ready to move without the need for slipping the clutch. Obstacles which used to require revving the engine and slipping the clutch are now accomplished with no slippage at all.

On the highway, I immediately noticed the lack of backlash that was present with the stock chain drive case. It also feels like a few extra horsepower have been freed up. This could be due to the gear to gear design and the use of bearings throughout the case.

Shifting takes getting used to, but once you learn the system it's extremely easy and has a very positive feel. From the look and feel of the unit I believe it's going to be an excellent long term investment.

Copyright 2000 Rick Horwitz Photography
All Rights Reserved