2005 Ultimate Adventure Ultimate 1975 K10 Part 2Posted in Ultimate Adventure: 2005 on May 1, 2005 0) (
Last month we laid out a plan to build up an Ultimate Adventure truck out of a 30-year-old beater as kind of a break from our norm of turning a late-model truck into a turnkey wheeler. But we thought building an everyman 4x4 like this '75 1/2-ton seemed cool because people actually wheel these things. We knew we had a wish list of parts we wanted to run and a few crazy things we wanted to try, but the first order of business was to find a shop insane enough to help us with the project. The techs at GM Truck Center in Burbank, California, are pros when it comes to solid-axle GM trucks and are experts on everything from lift kits to complete truck restorations. In no time our UAK10 was stripped down to cab and frame and sent out for a steam cleaning, while we hung out at the beach ... er, rounded up some parts back at our office. This month we show you how we cheated with a no-adapter-required engine swap, and prepped our Chevy truck for a Ford-style front Dana 60. In the next installment, we'll show you our brutally simple suspension plan and whatever else we can sneak in under our deadline.
Solid-axle Chevys are notorious for having frame problems around the steering box. GM Truck Center has fixed a hundred of them but as luck would have it, our '75 was one of the worst they've ever seen. John Hughbanks ground out the cracks and pieced the frame back together with a Hobart Ironman 250 MIG. To keep it from cracking again, Hughbanks added a reinforcement plate ($70) from J.C. Whitney and then bolted in an Off Road Design steering-box brace ($120) to keep everything in place.
Try not to puke on the screen ... but we're going to put a Ford transfer case in our Ultimate K10. We'll get to the "how" in a minute, but we'll start with the "why." First we tried to use an NV271 case from a Super Duty because it's got a great low range (2.72:1), fixed flanges on both outputs (32-spline front/34-spline rear), and a 7,890 lb-ft input torque capacity. Unfortunately they're also too wide to fit in the frame of our K10! So we went with the time-tested Ford NP205.
Why not the GM NP205? Well, the Ford version is more common than the GM. And all Ford 205s have the big 32-spline output shafts front and rear. Plus if you're like us and want to use your 205 behind an Off Road Design Doubler you need the big bearing input gear that the majority of Ford 205s have. Which bring us to the "how." By the nature of the $785 ORD Gen II Doubler ("Doubler Low-Low Range Transfer Case," July '05), your NP203 range can be adapted to work with a Dodge, GM, or Ford NP205 - which is perfect for us 'cause we want to run a '78-'79 Ford high-pinion Dana 60 (driver-side differential) front axle.
To keep things simple we could have bolted the Ram Jet up to our original TH350 transmission - and if it were in good shape we might have. But for the kind of use this truck was going to see, we gave TCI Auto a call and spec'd out a Truckmaster TH350. TCI recommended we go with its optional 2.75 ratio First gear (stock is 2.52:1) and a heavy-duty case (PN 311210) for $1,784. We put a lot of faith in TCI's products because every transmission it builds is for an enthusiast application. Everything in the transmission, from the friction material used to the way the shift feel is calibrated is done for a 4x4 that is gonna get used hard every time we get behind the wheel. Since we had our Ram Jet 350 on the hoist, we bolted the TCI TH350 to it with a flexplate for an '89 Blazer with a 350 ($43 at Autozone) and a 12-inch TCI torque converter ($269).
The strongest engine you could get in a '75 K10 was the optional 400ci small-block rated at 175 hp and 290 lb-ft of torque. That's nothing to brag about and wouldn't have been enough for 39-inch tires and a truck that's gonna weigh almost 6,000 pounds. Last month we told you that our buildup was going to require at least 350 hp, fuel injection, and would have to stay small-block based for weight and cost concerns. After crunching all the numbers, we just couldn't beat the value of the Ram Jet 350 ($4,900) from GM Performance Products. For the price of some aftermarket fuel-injection systems, you get the complete engine-oil pan to air filter-with the multiport fuel injection, computer, wiring harness, 350 hp/400 lb-ft of torque, and 2-year/24,000-mile GM warranty. The Ram Jet 350 can be installed in any vehicle that came with a small-block Chevy, but to make sure ours stays in place when Editor Rick Pw hammers it, we fastened it in with Off Road Design's competition-style motor mounts ($165).
While Hughbanks was manning the engine hoist, we slid under the truck to fit the original '75 crossmember back in place with new Daystar polyure-thane transmission mounts ($82). We didn't have to fabricate anything or use any adapters because it all went together like the stock parts did. The lowest point on our truck will still be the transmission crossmember, so we'll plan to build a skidplate to protect it and the TCI finned-aluminum transmission pan ($140) that holds two extra quarts of ATF.
Next month we'll pick up where we left off with the engine wiring, cooling, and fuel plumbing. We're probably gonna have to test fit a few different kind of headers to find some that will clear our driver-side driveshaft, yet still fit in the '75 framerails. And we're also tracking down a cheap accessory drive system that will let us run a serpentine belt--and maybe even get the A/C working again. If you've got one let us know.