Ultimate Avalanche - The Finale

We also had a vehicle speed sensor (VSS) added to the transmission as well as the tailhousing of the Atlas to give us many options when we finally get around to dialing the whole system in. For now the computer is run off the VSS in the adapter. We also had this custom transfer-case mount built that ties the adapter and the Atlas together and then uses a much larger Ford-style Energy Suspension transmission mount. This mount is wider than the GM style and spreads the load out a bit more.

Under the hood we found that the original air filter had gotten wet on the trip and practically got sucked into the engine. We added an Airaid intake and filter to try and get some better airflow, providing we stay out of the deep water. We didn't notice any added noise from the intake, and the installation was easier than spreading peanut butter on Wonder bread. It's hard to tell if the claimed 18hp gain arrived on such a big truck, but our seat-o-pants dyno did notice some change. We really like the 8.1L GM motor even if it takes our whole paycheck to fuel it.

We've also had a few issues with the ring-and-pinion in the back of the Avalanche. We realize now that going from the stock rear 14-bolt to a low-pinion Dana 60 was maybe not the smartest idea. (The 14-bolt has a 10 1/2-inch ring gear over the 9 3/4-inch 60.) But then to add weight and traction on bigger sticky tires only compounded the problem. The first gearset was not broken in as per instructions and was found busted after The Carnage, while the second set was being abused on asphalt when they gave up the ghost (power braking a 9,000-pound truck can break things), so we are willing to take the blame.

Another issue that arose with The Carnage was that we actually twisted the splines on our 300M CTM axles. The best axle design is one where the shaft diameter is smaller than the root diameter of the splines as seen on the left. The old shaft on the right allows for the twisting in the splines since they are weaker than the shaft itself. When the shafts neck down after the splines, the twisting force actually works like a torsion bar, giving the shafts more spring to deal with shock load. CTM now makes all its shafts this way, and it keeps the twist away from the splines where it can start to cause breakage.

What type of abuse are you giving your truck when you can put a crack like this in your 1/4-inch-thick bumper? Other than this one crack we were totally pleased with our Trail Ready front bumper. It didn't flex or bend under heavy winching, and it was bounced off quite a few obstacles.

We had some problems with axlewrap from running the 66-inch springs in the rear with the big tires and torque, so we took the Avalanche to Atlas Spring to get a military wrap and an antiwrap spring added to the front of our current rear packs. The military-wrap leaf replaces one of the old leaves and comes up over the spring eye for added strength, while the antiwrap leaf goes from the U-bolt plate to the spring eye and resists the front of the axle coming up under acceleration.

The new leaves greatly reduced wrap on the back end and the truck had a noticeable difference off the line. However, we did eventually add a traction bar as well.

The original rear spring perches were the open-ended style and we actually collapsed them on the trip during excessive spring wrap. Here you can see the ghetto trail repair we did to them.

The tires and wheels performed excellently, but unfortunately we've swapped them off the truck. The Walker Evans bead locks have worked flawlessly, never lost air pressure on any of our long trips, and spin true even after a year of abuse. The BFGoodrich Krawlers are great tires for off-road, and our 39-inch variant never failed us on big rocky climbs. However, the rubber compound used to make these prototype tires is very soft for the competitive rockcrawlers and works exactly as designed in that terrain, but it doesn't hold up to the big weight of the Avy on the street.

The front tie rod was another reoccurring issue. It seems that some rookie driver kept running it into rocks while out wheeling, and it almost ruined his birthday party at Johnson Valley last January. An upgrade was made in the fab shop at Off Road Unlimited. The new shaft is 1 5/8x1/2-inch-wall tubing, and though it makes up for 30 pounds of the Avalanche's girth, it hasn't bent yet. Also the upgraded tie-rod ends are almost entirely threaded into the shaft, giving them much more strength.

The wildest thing we did to this truck was put rear steering on it, and many people have asked us about it, so we'll touch on that again. The rear-steer setup from Performance Off Road Systems and Stazworks has never left us stranded or been a detriment, though the original setup has been changed to work better. The turning radius is great, the return to center feature is a bonus over any other system we've used, and the novelty will never wear off. Our biggest problem was that the steering arms on the knuckles were too low, and the mini tie rods would hit the rear leaf springs.

We fixed this by contacting OTT Engineering and got two new arms with a 2 1/2-inch raise. We welded these arms to the original Dynatrac 1-inch arms and used longer bolts to hold the whole thing in place.

The most recent problem to arise is the front driveshaft hitting the transmission. We upgraded to a front shaft running a 1350 CV from High Angle Drivelines, and have had no strength or angle issues with it. What we did notice is that we need some front bumpstops because the driveshaft comes up so far it will hit the shifter of the transmission. While in Moab, we broke the connection knob off the shift arm and did this zip-tie repair job.