When you try something that hasn't been done before you can run into some issues; as with any project vehicle, our Ultimate Avalanche was swinging from fun to frustrating. When we last checked in, our 2003 Chevy Avalanche was stripped and on the rack at Off Road Unlimited, plus we had just picked up two brand-new axles from Dynatrac. The plan was simple enough: Put the axles under the truck, use suspension components from our friends at Tuff Country, and add an Atlas transfer case for good measure. The problems arose when we wanted to incorporate our special rear axle with rear steer, and make the computer-controlled transmission communicate with the geardriven transfer case.
In the end almost everything worked, and we only had to throw a few things across the shop in frustration. You would think that being big-time magazine guys, we would have all the cool stuff and not have any problem building a rig, but that is only slightly true. We do have all the cool stuff, it's just tricky to put it all together on an unusual platform. Follow along as we get our Ultimate Ulcer--er, Avalanche--closer to being a trail-taming freak machine.
The guys at Off Road Unlimited were excited to see us every morning, though it was probably more because of the Krispy Kreme donuts than because of the bright and shiny attitude. Mauricio Natera was happy to install some brackets from which to hang our Tuff Country springs on the front of our Av. Off Road Unlimited has done many solid axle swaps in the past, but never on an Avalanche. | 
Next we stuck our Dynatrac Pro-Rock 60 under the front of the truck. We decided on 6-inch lift springs, though we may go to 4-inch springs eventually if the truck sits too tall. We like our vehicles low, but with as much ground clearance as possible. The front will also be getting two Tuff Country SX8000 performance shocks on each side. | 
In the rear of the truck we had a few rules we wanted to stick with. No lift blocks because we don't like axlewrap, and narrow springs because we had a special rear-steer axle made and we didn't want the tires to hit the springs. Our solution was to move the springs under the frame instead of out on the sides. This should meet all our needs by allowing us to run a lower lift spring and possibly give better articulation since the axle will now have more leverage on the springs, though towing may be a bit scary. We started by building front spring hangers for the frame from some 1/4-inch plate. |
For the rear shackles we had a few obstacles. First we needed to box the frame and then cut a hole and sleeve it. For this as well as most of the other welding we used Miller Electric MIG welders. | 
Then we did some mocking up to see where the springs would extend to on full stuff and at ride height, and finally we made some shackles and bolted everything up. | 
Initially we planned on going spring-under. Though this seems archaic to some folks, we felt the loss of ground clearance would be offset by also losing almost all the axlewrap. We even went so far as to get this awesome spring-under U-bolt plate kit from Dynatrac. The biggest problem we ran into was that the 6-inch lift springs we had were still just too short for the truck. Finally we changed directions and went spring-over in the rear with Tuff Country 3-inch lift springs. This ended up working out perfectly and left just enough room for the rear-steer components, which we will touch on next month. |
Because our rear axle has steering knuckles, we needed a way to lock it out for highway driving. For this we asked Karl Knoll to do some extreme machining for us. Knoll works at Off Road Unlimited and loves to make things with the lathe and chromoly. | 
We also contacted Aurora Bearing for a set of its 3/4-inch rod ends. We recommend these lockout bars running from the steering knuckles to some custom tabs welded to the axletube for any street-driven rig with rear steer. Though it's a slight hassle to remove them before hitting the trail, it is good insurance. | 
We could've kept the NV246 and converted it to bolt-on yokes, but we didn't want the front driveshaft spinning all the time. A 4.3 Atlas transfer case from Advance Adapters would solve all of our problems and give us a better low range. |