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2000 GMC Sierra Half Ton Z71- The Ultimate Z71Part V: Drivetrain From the December, 2008 issue of 4Wheel & Off-Road By Ali Mansour Photography by Ali Mansour
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Sometimes it's all about the stuff you can't see. Without question the unsung heroes of most 4x4s are the hardworking drivetrain parts that translate power-namely your transmission and transfer case. When building a rig for the Ultimate Adventure, the goal is to make it as bombproof as possible. But bombproof doesn't always mean UA-proof. Remember, it's the Ultimate Adventure, not the sort of moderate "I will just trailer my rig from place to place if anything goes wrong" adventure. Getting It Done * Teardown... Getting It Done
* Teardown (Aug. '08)
* Bobbing and Welding (Sept. '08)
* Body Protection (Oct. '08)
* Suspension (Nov. '08) With our '00 GMC Sierra 1/2-ton built from the factory with a driver-side drop configuration, we knew we were in for a bit of a challenge as our front junkyard Dana 60 axle had the differential on the passenger side. Now believe it or not, this is not as big of a challenge as you might think. Obviously your transfer case will need to be set up for the correct side, but the two biggest challenges generally faced with a swap like this is transmission width and engine oil-pan clearance. Working with a fullsize rig gives you more room to work around problems, and sometimes the solution is as easy as getting a custom driveshaft built. OK, I'm not saying that it's just that cut and dried, but if you are a confident fabricator with a bit of 4x know-how, it's something that you should have no problem tackling. Keeping our Super Sleeper build going are Mel Wade and his squad of pro fabricators at Off Road Evolution. With the crew pulling out all the stops and kicking in the long hours, we geared things up with Off Road Design's NP203/205 Doubler and slid in a 15,000-pound Warn winch behind the GMC's modified factory bumper. Check back next month as we wrap up our Ultimate Z71 build and show you some of the damage it survived. And for all of you who just can't get enough Z71 action, cruise over to our website, www.4wheeloffroad.com, for the entire series of web-exclusive extras that chronicles the build from the teardown to the Adventure.  1. The Warn M15000 winch is...  1. The Warn M15000 winch is an almost perfect fit between the Sierra's 1/2-ton framerails. Though we could have easily opted for a higher mounting location, we wanted to keep the winch low and tucked behind the bumper to keep the overall appearance of the truck as stock as possible.  2. We modified an older Warn...  2. We modified an older Warn mounting platform and welded it in and reinforced the frame since our tow points will be attaching here as well. With the factory bumper mounts removed, we fabricated a set of weld-on tabs that moved the bumper up an additional 2.5 inches to allow more clearance and easier access to the winch.  3. The GMC's stock bumper...  3. The GMC's stock bumper was a little flimsy after we trimmed it up, so to make it more trail-ready we went to work with a sheet of 3/16-steel. Using the bumper's new shape we cut out caps to cover each end to add rigidity and strength, and then TIG-welded them in place.  5. The Advance Adapters tailshaft...  5. The Advance Adapters tailshaft kit comes with a new output shaft, an output-shaft seal, a reluctor ring, and a sensor. The new reluctor ring is what your speed sensor reads, and since it is now in front of the transfer case it will not think the vehicle's transmission is slipping when it's in 4-Lo. This prevents the electronically controlled transmission from putting the truck into limp-home mode, for if the sensor were still located in the transfer case the transmission may believe that it is slipping when the 4:1 gear reduction is engaged.  6. Complete with new shift...  6. Complete with new shift linkage, the Off Road Design Doubler works by mating an NP203 reduction unit with a complete NP205 transfer case. This setup offers you both a 2:1 low range, and when you really need to make your fullsize crawl, you simply shift the NP203 into gear and you've doubled your low range.  6. Complete with new shift...  6. Complete with new shift linkage, the Off Road Design Doubler works by mating an NP203 reduction unit with a complete NP205 transfer case. This setup offers you both a 2:1 low range, and when you really need to make your fullsize crawl, you simply shift the NP203 into gear and you've doubled your low range.  7. Keeping our transfer case...  7. Keeping our transfer case and transmission tucked high is a custom crossmember from Off Road Evolution that hard-mounts to the case and adapter and then connects to four bushings that mount the member to the frame. The bushings help deal with the normal drivetrain vibes, and with the crossmembers tied into one another they prevent everything from twisting under a heavy load.  8. Always a crucial element...  8. Always a crucial element to any drivetrain, a set of beefy driveshafts from J.E. Reel were bolted in. Both outfitted with CVs at the transfer-case end, our front shaft was made with a 2-inch outside diameter to help clear the transmission and oil pan.  9. Friction and heat can destroy...  9. Friction and heat can destroy your drivetrain without warning. One of the easiest ways to battle the hot stuff is by equipping your drivetrain vitals with synthetic fluid. We went with one of the leading names in synthetics, Mobil 1, to lube up everything from our transmission down to our differentials.  10. Since we shortened the...  10. Since we shortened the front of our bed by 12 inches, the stock gas tank would no longer work. Making the best use of our limited space, we purchased a 32-gallon Jazz fuel cell and dropped it in between the framerails and through the bed. Incorporating our rear cage bars as chassis stiffeners, we laid our 40-inch BFG KM2 M-T between the two for a low and flat spare-tire mount. This gives the UA Z71 better rear visibility and allows the bed to remain more open.  11. With the cell in place,...  11. With the cell in place, we used AN fittings and fuel line from Russell to plumb the new external fuel pump, filters, and delivery lines. When swapping to an exterior pump, it's important to mount it close to the tank and far from any heat sources such as your exhaust.  12. Known for legendary winches,...  12. Known for legendary winches, Warn has moved into the air-compressor world with its VTC onboard compressor. Mounted in the bed of our Z71, this little compressor comes in handy as it fills everything from 40-inch tires to air mattresses with reasonable quickness. Electric Avenue
Modern vehicle electronics can be a real pain when performing such an extensive conversion like we have done. Through a series of cut wires, swapped ECMs (electronic control modules), a disconnected BCM (body control module), and an eliminated four-wheel-drive module, we somehow tricked our truck into working. We wish we could retrace each step with you in the magazine, but our current configuration is a bit smog-challenged and we are still working out a few of the bugs. As far as we can tell, if you have disconnected the 4WD module (behind the driver-side dash) and the vehicle's speed sensor is monitoring only the reluctor ring that now rides on the transmission output shaft, everything should shift and work fine. Keep a look out for future blogs and articles that will address all these new-age electronic hurdles, and hopefully one of these days we can have a dash that will stop blinking at us!
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