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2005 2WD Chevy Tahoe Solid Axle Swap - Rosco P. Drivetrain: Part 1

Posted in Project Vehicles on February 26, 2015
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When you learn that you and your wife are expecting not one baby but twins, your priorities change quickly, and so does the future of your savings account balance…and sometimes your vehicle fleet. Before this news, we were pretty happy buzzing around in our small family’s wheeler, a mildly built two-door Jeep Wrangler JK. With the news of a larger than expected change in roommates, we realized that a two-door JK is less than ideal for a family of four, plus dogs. Hoisting one baby in and out of a rear-facing car seat in the back of a two-door JK doesn’t sound fun. Add a second baby and you realize the short Jeep’s goose is cooked. Also, our JK was too nice and worth too much money to be subjected to the impending puke, pee, poop, spilled drinks, and lost snacks that the two rug-rats would bring to any future 4x4 we owned. And we can’t lie—we are always looking for an excuse to start another project, so why not change directions a bit?

An easy yet hardly inexpensive solution would be to look for a four-door JK. We could spend $25,000-$40,000 on a used JK Unlimited, swap in heavy-duty drivetrain, and dream about engine swaps, but we like being different, and babies need expensive stuff like diapers, toys, food, and college tuition (or so the wife says). The JK route would work, but we knew the savings account was going to be hemorrhaging soon, so our answer is a less expensive—and “different”—platform to start with.

One vehicle having great potential is the 1999-2006 Chevy Tahoe/GMC Yukon. Sure, GM’s independent front suspension is inadequate at best for most of the four-wheel-drive trails we hit, but these trucks have reliable Gen III GM V-8 power, established transmissions with known issues (and fixes), and great parts availability. Add in a solid (and easily modified) frame, four doors, and coil and link rear suspension, and we are getting somewhere. These SUVs are inexpensive for the amount of vehicle you get, and they are available at various trim levels, from leather-wrapped to cloth and vinyl. If we were planning on a Jeep JK–based family wheeler, we would upgrade the suspension, axles, and powerplant. With a Tahoe or Yukon, we only have to add a solid front axle and front suspension and use aftermarket suspension parts for the rear, but we’ll also be upgrading other parts like the rear axle, transfer case, and so on. Sure, the work in the front is more difficult than just bolting in premade parts (as we would with the JK), but working with a lower-cost initial vehicle should save us money in the long run. With a plan in mind, we started scouring the interwebs for a good Tahoe/Yukon as a platform for our Wrangler-fighting family wheeler.

We took the 2WD Tahoe on some backroads one time, and it didn’t go so well. We didn’t get stuck, but we did destroy one of the low-profile police car’s tires. Bigger tires, 4WD, a winch, maybe some lockers—we had a long to do list by the time we limped the cop car home. Before we got a thousand miles on the truck we had it on jackstands in the driveway.

We came across a two-wheel-drive ’05 Chevy Tahoe that was a former Henderson, Nevada, police car. We had to have it. The 2WD part of that sentence makes sense in the long run due to the reduced computer systems we will be bothered with. The back seat of a police car is about as baby-puke-proof as any vehicle due to the vinyl and rubber interior. Plus, cop cars are cool (just watch The Blues Brothersif you don’t know why). This Tahoe, like many, has one of the best A/C systems we’ve ever encountered, meaning our new family will be nice and cool no matter where we go in the desert Southwest.

The truck has a 5.3L Gen III V-8, a 4l60E transmission, and a few leftover police car parts (which we’ll talk about later). Our plan is to keep things simple while adding beef and durability in a way that is easy to duplicate by any reader with twins on the way, so you too can have a family truckster without taking a second mortgage or feeding babies ramen noodles for life. Things don’t always go as planned, but with any luck our Tahoe will be back on the dirt road before the twins are old enough for their first adventure.

We kept hoping that we’d find something cool in the back seat (a stack of $100 bills, a .38 special, a stolen Rolex). All we found was a package of cigar papers wedged in the bumper and an old siren behind the grille. We plan to build a prerunner-style tube bumper that will hold a winch just in case we get stuck later on. The truck also needs a good name. We contemplated calling the it House Arrest or Moving Violation. Maybe Hot Pursuit or Baby’s on Border Patrol?

We pulled every bolt-on front suspension components off the Tahoe since the quickest way to reliable four-wheel drive is a solid front axle. It’s surprising how easily all the old parts fell off the truck.

We broke out the plasma cutter to hack off the old A-arm mounts. In ’00 models GM used an undercoating that seems to be exactly like black crayon, and when we added heat from the plasma cutter this waxy substance melted and ran off like hot coffee. Clean it off well with cleaner so you can have a good surface to weld to.

We used a 4 1⁄2-inch angle grinder to clean off the rest of the mounts from the frame, being careful not to gunk up the grinding wheels with undercoating. The framerails will eventually have a new suspension designed to support the body above a solid front axle.

Our Tahoe had the same suspension as a 4WD Tahoe but without a front diff, axleshafts, or a transfer case. We can now add a case that uses a shift lever (most ’99-’06 Tahoes come with an electronic shift NP243). Also our Tahoe’s computer, unlike the one on a 4WD Tahoe, won’t freak out searching for a missing front axle or shift information from its T-case because it never had either.

Here’s the beef that will replace all those spindly little front suspension components, a Dodge AAM 91⁄4 front axle from a ’12 3⁄4-ton truck that we bought for $800. A big enough axle that should provide years of reliable service with 37-inch tires, lockers, and low gears. It is debatable whether the AAM front is a better axle than a Ford high-pinion 60. The AAM axleshafts are slightly smaller (33-spline). The ring gear is only 91⁄4 inches compared to a Dana 60’s 93⁄4. The AAM housings can bend when abused under a heavy diesel truck. However, the AAM uses bigger U-joints and massive brakes and has integrated speed sensors that we hope will work with our GM PCM.

For the rear of the truck we ran down to our local pick-a-part, where we found a late-model GM 14-bolt with factory disc brakes. It cost about $270 with a core and will be overkill for the abuse and large tires this truck will receive. But we like overkill when it comes to the truck our new screaming, pooping, and puking family will be riding around in.

We also came across this NP241C from a Chevy truck. It was our favorite kind of junkyard find because someone else had already done most of the work by pulling the transmission and rear driveshaft and unbolting the transfer case. All we had to do was remove the front driveshaft and take the transfer case to the checkout, where we bought it for $85 with a $10 core. We also found the 4WD tailhousing from a 4L60E for $5. Combine that with a 4WD 4L60E mainshaft and we have the makings to convert our 2WD 4L60E into a 4WD transmission that can mate to our junkyard transfer case.

With the NP241 and GM 14-bolt back home we pulled the Tahoe’s 10-bolt rear axle. Our plan is to swap the factory four-link (with track bar) brackets from the 10-bolt to the 14-bolt and add aftermarket rear lift springs and shocks. After a little well-planned fenderwell trimming we should be able to fit 37s without making the truck so ridiculously tall that it’s unstable off-road when packed with kids.

With the factory rear axle pulled we placed the two axles next to each other so we could transfer the factory suspension brackets over. We set the pinion angles equal between the two axles and started measuring and cutting. Before you cut anything off the old axle you need to measure exactly where the brackets mount so you’ll be sure to get the brackets in the right place on the new axle.

By cutting close to the welds with a plasma cutter we can reuse the brackets. The old 10-bolt axle might be junk when we are done with it, but we can pull the brakes, shafts, gears, and diff and sell them to recoup some of the cost. If the plasma cutter nozzle won’t fit in a spot, try a 41⁄2-inch angle grinder with a cutoff wheel or the blade on a Sawzall to cut the factory welds.

After measuring, and with the angles of the flat surfaces of the old brackets noted, we cut off and cleaned up the brackets using our grinder with both a stone and a flap wheel. Some of the radiuses of the brackets also have to be opened up to clear the larger axletubes of the 14-bolt. Cleaning up the weld surfaces of both the brackets and the axle tubes helps the welds be much stronger.

Once the axle brackets are cleaned up and we’ve checked the fitment on the axletube we need to duplicate the angles of the brackets from when they were on the 10-bolt and make them match when installed on the 14-bolt before tack-welding them in place. Tape measures and an angle finder are key. Make sure to measure twice, tack-weld the part in place, and then completely finish your suspension before fully burning in the brackets. Also we will be using adjustable control arms to help set pinion angles and make sure the suspension cycles properly. These should be installed before we do any final welding. We’re just getting started. We have lots more driveway tech to share with you next time in Rosco P. Drivetrain, Part 2.

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