PART 4: THE ULTIMATE T-CASES FOR OUR ROVER
PART 4: We’d recommend this drivetrain combination for just about any 4x4.
LIKE MOST FOLKS WE LIKE TO think our vehicles are more than just a little unique. That’s even easier to do when you start with an uncommon starting point like our 1989 Range Rover Classic. There may be Range Rovers in Europe, South or Central America, Asia, Africa, or Australia that are bare bones, have a turbodiesel, and a five-speed manual (deranged), but most of the remaining examples in the U.S. are normally going to be slathered in leather, replete in electronics, and powered by that Buick-derived aluminum V-8 oil leaker spinning some sort of automatic transmission. And while we have covered the details and installation of the Dana Ultimate Dana 60 axles (“Derange Rover,” Part 2, Sept. 2018; bit. ly/2zya0eK) and hinted at the Cummins R2.8 engine (we’ll talk more about the finer points of the engine install in subsequent stories), the manual transmission and transfer cases (yes, there are more than one in the Derange Rover) are some of the most important parts that make our Deranged Rover more than a little unique—especially in the US. And handsdown, our favorite T-case system is the Magnum Box doubler setup from Offroad Design that will really push the Derange Rover’s on- and off-road capability.
One way or another, all this sounds like a great combination to us; namely a midsized SUV with plenty of torque and a multitude of gearing options for the road and trail. So with a little research and the right parts from the right aftermarket companies (some of whom just happen to be supporters of the 2018 Ultimate Adventure) we can have what may be the world’s most capable Range Rover. The best part is you, too, can duplicate this build. We’d recommend this drivetrain combination for just about any 4x4, from daily driver to full-on, one-off trail buggy.
If you’ve read this far in the issue you know we’ve completed the 2018 Ultimate Adventure and can attest to how well this combination of parts works in the Derange Rover. The rig has plenty of torque for the road, even fully loaded and at highway speeds. The NV3550 five-speed shifts well and seems more than fitting behind the clatter of the Cummins R2.8 Turbo Diesel (we’re testing a new tune from Cummins that allows 310 lb-ft of torque and 161 hp). The Offroad Design Magnum Box planetary low-range and Ford NP205 provide plenty of gearing for the most technical crawling at 5.33:1 with both boxes engaged, while the 2.72:1 Magnum and 1.96:1 NP205 ranges allow for the wheel speed necessary for slick eastern mud/rock trails. Also, the front- and rear-dig capabilities make negotiating tight trails a breeze.
So, how did we assemble these parts? Check it out!
1 We know, we know. Automatic transmissions are the wave of the future (since the
1950s). But we like pushing a clutch pedal and stirring the gear oil ourselves. Still, keeping that Cummins R2.8 in its power band is important to maximizing the fuel economy possible from this engine. A six-speed manual would be nice, but there isn’t really a good medium-duty option, so we stuck to a transmission we know well. The NV3550 came in Jeep SUVs from roughly
2000 to 2004. The transmission has a 4:1 First gear, a 3.57:1 Reverse, and a 0.78:1 overdrive. Our NV3550 seems to have come from a 2002 TJ (says “02” on the bell), and since it says “good” on the outside in junkyard paint and is full of oil we simply slapped it in. The transmission came from our good buddy and UA crony Keith Bailey, from the Off-Road Connection in Fultondale, Alabama. We picked it up in Moab during Easter Jeep Safari 2018.
2 With that transmission in mind it was easy to call up longtime UA sponsor Offroad Design (Carbondale, Colorado) for one of its Magnum Box planetary underdrive units coupled to a Ford (driver drop) NP205 transfer case. This gives us a ton of gearing options as well as independent front and rear drive capabilities. The guys at ORD built the unit to bolt onto the
NV3550 and with bulletproof 32-spline front and rear output shafts. A pair of 1350 doublecardan driveshafts from JE Reel Drivelines and a pair of corresponding 32-spline flanges will send the R2.8’s torque to the front and rear Ultimate Dana 60s.
3 To couple the Cummins R2.8 crate engine to the NV3550, we contacted our friends at Axis Industries. Axis makes adapter parts that are second to none and blur the line between adapter parts and artwork. We used the company’s bellhousing adapter ring and studs last year on the official 2017 Ultimate Adventure vehicle, the UACJ-6D, but since then Axis has changed a few things.
4 One change that Axis made to the R2.8L– to–Jeep 4.0L adapter kit is that the kit now includes a fabricated replacement R2.8 flexplate instead of the customer having to send in the original Cummins flywheel to be machined down. Then a crank hub adapter bolts to the R2.8’s crankshaft. This kit works with the Jeep NV3550, AX15, and NS6G370 six-speed transmissions. We prefer the five-speed NV3550 or AX15s since in our experience the six-speeds aren’t as durable.
5 We bolted a Jeep 4.0L flywheel from Centerforce (PN 400469) to the crank hub adapter from Axis. A Centerforce Performance Clutch Disc (PN 384193), a Centerforce II Pressure Plate (PN 361890), and throw-out bearing for a 2002 TJ Wrangler (PN N1764) round out the clutch package. Don’t forget a clutch alignment tool!
6 We used some Daystar poly body bushings for a CJ-5 and a 2002 TJ Wrangler transmission mount, together with some bits of steel from Offroad Design and our scrap metal pile, to isolate the transmission and transfer case from the Rover’s frame. We later added more 2x3x0.188-inch rectangular tubing and some angle iron to form a transfer case crossmember.
7 With a firm plan in place to set the drivetrain as far to the passenger side of the framerail as possible (about 1 inch offset from centerline), we slid the assembled transmission and transfer cases under the Rover. Using a couple of floor jacks and heavy-duty ratchet straps to act as safety belts, we lifted the unit between the framerails.
8 We then assembled the engine to the transmission and placed the whole kitand-caboodle where we wanted it. This allowed us to fine-tune the placement of the T-case crossmember, bolted and heavily tackwelded in place as shown here.
9 A few holes had to be cut in the floor of the Rover for clearance of the massive NP205 T-case. Also, we are switching from the factory passenger-drop T-case to a driver-drop unit to match the Ultimate Dana 60s. This unit, and the Magnum it lives behind, will absolutely hold up to everything we can throw at it and then some.
10 With everything fitting in place we dropped the tack-welded transmission/ transfer case crossmember and finish-welded the part. We added several small triangular and plate gussets to the crossmember. The whole drivetrain sits flush between the framerails, allowing the Derange Rover to have a flat belly. We may add skidplates to the bottom later on, but for now this will do what we need it to.
11 To shift the NV3550, we selected a B&M Precision Sport Shifter (PN 45048). This stainless steel and billet shifter is engineered for 1999-2004 Jeep Wranglers with NV3550 manual transmissions, and it shifts with crisp authority. To toggle the Magnum Crawler Box and NP205, we installed Offroad Design’s transmission adapter twin-stick NP205 shifter and one of ORD’s floor-mounted Magnum shifters. These shifters work like butter and, coupled with the precise machining in ORD’s Magnum and rebuilt NP205, provide the crispest T-case shifting we’ve experienced on the trail no matter the situation.
12 Connecting the NP205 twin-stick shifter goes a little something like this. The throw and placement of the sticks is variable thanks to the adjustable nature of this shifter. The floormounted shifter for the Offroad Design Magnum Box was easy to mount to the Rover’s high and flat transmission tunnel. Shift linkage was easy to customize for this application and should be simple in lots of other 4x4s. You can also see the anodized blue aluminum of the B&M shifter in front of the Magnum Box’s linkage.