<%@LANGUAGE="VBSCRIPT"%> ROCKCRAWLER.com - Atlas II Installation Part II

ROCKCRAWLER.com
Advance Adapters Atlas II, Part II
By Chris Shontz

Discuss This Article Send this article to a friend!

This is the second of three features (read Part I) that focuses on the Atlas II Transfer Case, manufactured by Advance Adapters. This feature will take a look at the installation of an Atlas II in a moderately-configured Jeep Wrangler TJ, with a six cylinder engine, an AX-15 transmission, a stock crossmember, and no body lift. We will evaluate its performance both on-road and on the trails in the third and final installment.
Atlas II Install

Our Atlas II was installed by Steve Christopher; a technician at OK Auto, 4wd & Tire, in Stewartsville, New Jersey. Steve had installed many Atlas II transfer cases prior to this one, and is known for his clean and professional work.

Atlas II Install The Atlas II Installation Guide is available online for download in PDF format from Advance Adapters' website. It contains detailed installation instructions and complete technical information for most any application.
Getting right to business, Steve cleared away the center console and disassembled the transfer case lever and linkage. The shift knob and boot needed to be removed first and then the center console comes out easily by removing a few screws. Our 1999 Wrangler had a passenger air bag defeat switch at the head of the console which was easily set aside without having to be disconnected.
Atlas II Install
Pulling out center console.
Atlas II Install
Exposed tunnel.
Atlas II Install
Disassembling lever bracket.
Atlas II Install
Removed transfer case lever.

Once the transfer case lever was removed, it was time to disassemble and remove the old NP231 transfer case. Steve began by dropping the crossmember and continued by disconnecting the front and rear driveshafts, speedometer gear, and miscellaneous wiring harnesses. Finally, he spun the nuts off the studs around the transfer case input to disconnect it from the transmission and set the stock transfer case on the floor.

Atlas II Install
Assembled transfer case.
Atlas II Install
Disconnecting the crossmember.
Atlas II Install
Exposed transfer case.
Atlas II Install
Removing the transfer case.
Atlas II Install
Transmission output.
Atlas II Install
Disconnected transfer case.
   

After the old transfer case was removed from the Jeep, it was time to begin preparation of the Atlas II transfer case. The initial preparation begins on the bench. This involves removing several red plastic caps and seals, put in place before shipping to keep contanimates out of the dry transfer case.

The Atlas II is clocked by inserting studs into their respective positions around the input circle. Clocking, or rotating, the Atlas II allows you to find the position that offers you the best ground clearance once installed. Be sure to leave a little room over-top of the Atlas II to allow the driveline to move during extreme off-road use without hitting the floor pan.

Our stock transfer case had a stock rotation of 13 degrees, and after doing a trial fitment, we determined that the Atlas II fit best at the 21 degree position. If you are facing the uninstalled Atlas II input, and looking at the top-most series of holes around the input circle, the 21 degree position is the 2nd hole in from the right.

Once the Atlas II was in place, we installed the stock speedometer gear into the output housing and Steve preassembled the shift linkage. This preassembly was necessary to ensure proper operation of the Atlas II and to determine what tolerances would be required to properly fit the new transfer case under the vehicle.

Atlas II Install
Install speedometer gear.
Atlas II Install
Partially-installed input studs.
Atlas II Install
Linkage being assembled.
Atlas II Install
Assembled linkage.

The Atlas II is much larger than the NP231 transfer case it replaces. With the Atlas II installed, the unmodified bracket that mounts the drivetrain to the crossmember no longer fits properly. It would normally bolt up to the bottom of the transmission, extend underneath the transfer case, and bolt to the crossmember beneath the transfer case. Modifying both the bracket and the crossmember allows continued use of the stock mounting hardware. In the case of the bracket, it is literally cut in half so that it no longer extends beneath the transfer case. It now extends straight down from the transmission where it meets the crossmember.

It should be noted that we followed the instructions for making these crossmember and bracketry modifications in the "TJ" section of the provided installation manual, but we took careful measurements prior to doing so, because every vehicle is different - especially if equipped with a body lift or a high-clearance crossmember.

Atlas II Install
Mark and measure changes.
Atlas II Install
Cut bracket.
Atlas II Install
Completed modification.

The modifications that need to be made to the crossmember are much more involved. The installer should have sufficient metal-working skills to ensure proper fitment of the Atlas II transfer case. Steve took measurements and cut a gap in the boxed section of the crossmember to allow clearance for the left-hand drop portion of the installed transfer case.

After cutting the cap, he started work on the forward portion of the crossmember that allows the transmission mount to seat correctly. In this case, he had to cut around the front three sides of the forward mounting slots that are used to provide a mounting location for stock drivetrains with automatic transmissions. Once three sides were cut, he used a hammer to bend it up at an angle to match the original mounting position. Steve then welded the forward mounting surface into its new position.

Atlas II Install You may be able to avoid or simplify this modification. There is a plate that seats itself over these forward mounting holes in the same manner as our modification. I believe this plate provides the mounting surface on the crossmember from drivetrains equipped with an automatic transmission. You should be able to find one at a junkyard, and it should make things a bit easier if you don't already have one. If you have a body lift, another option is Skyjacker's flat skid plate, which includes a mount similar to the one pictured.

As a finishing touch, Steve welded up skid rails that would protect the low-hanging transmission mounting bolts from getting shaved off or damaged by the terrain.


Atlas II Install
Taking measurements.
Atlas II Install
Marking the crossmember.
Atlas II Install
Cutting the gap.
Atlas II Install
Scooping out the trail scum.
Atlas II Install
Sealing the boxed section.
Atlas II Install
Welding the seal plates.
Atlas II Install
Completed gap.
Atlas II Install
Gap and forward mount.
Atlas II Install
Welding skid rails.
Atlas II Install
Completed skid rails.
   


With the crossmember and bracketry modifications complete, it was time for another test fit. What I'm not showing you is that this is only one of many "test fits". Throughout the entire process, Steve had the Atlas II transfer case in and out of the Jeep several times to make adjustments. A good part of the installation process was trial and error, but if you have enough patience, the tedium pays off. Be careful when you mount and unmount the Atlas II so that you do not damage the studs. Try to slide it on and off straight and slowly.


Atlas II Install
Atlas II on transmission jack.
Atlas II Install
Steve adjusts Atlas II on jack.
Atlas II Install
Raising Atlas II into position.
Atlas II Install
Lining up splines and the studs.
Atlas II Install
Installed on transmission.
Atlas II Install
Fitting the crossmember.
   


CONTINUED --->>>

 

Help spread the ROCKCRAWLER world!           Share on Facebook





©1997-2013 ROCKCRAWLER 4x4 and Off-Road Magazine. All Rights Reserved.

RockCrawler.com   -   IH8MUD.com