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Ultimate Chevy K10 Revival

Posted in Project Vehicles on October 1, 2011
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Our Ultimate K10 is getting close to exceptional again. To bring first-time readers up-to-date, we built this ’75 Chevy for the 2005 Ultimate Adventure. It tackled some of the country’s toughest trails on 39-inch BFGs. Then the truck was parked and pillaged. Even its license plates and insurance fell to the wayside. To get this popular truck back in circulation, we are doing a budget-conscious street/trail buildup. It will ride on 37-inch Mickey Thompsons and will be able to hold its own on the trail and also spend time as a Jeep-tower .

Offroad Design’s crossover and high-steer upgrades, coupled with ram-assist, are straightforward straight-axle steering improvements. Tracking will be straightforward too.

This month we continue the undercarriage upgrades. Unfortunately, most of the previous ram-assist steering system migrated to other projects. Those parts worked well, and we’re basing the new system on the former one.

Power Steering Power Parts
The OE steering system was engi-neered to work with factory-sized tires and leverages. When rolling mass in-creases by about 25 percent (29-inch stock tires compared to 37s), deficiencies are magnified. Tracking can be a handful thanks to inadequate linkage geometry. Maneuvering aired-down meats through boulders is an exercise in biceps/triceps building.

Our plan of attack is twofold: mechanical/structural improvements followed by hydraulic upgrades to provide more force. Offroad Design helped create the setup, which had proven effective, so we turned to proprietor Stephen Watson once again to upgrade our K10’s steering.

A ’68-’87 Chevy/GMC 4x4 Achilles’ heel is the frame area where the steering box mounts. Even in stock GM solid-axle 4x4s, the frame is prone to cracks here. Better to be proactive than attempt to rig the steering box to a ripped frame to get off the trail.

Our K10’s frame was fractured prior to the initial build in 2005. GM Truck Center fixed it then, welding the frame and adding an Offroad Design brace that triangulates the framerail to the front crossmember (highly recommended with 37-inch and up tires). This time, GM Truck Center ground the frame down near the original steel, then welded on its version of the age-old two-piece reinforcement kit. GM Truck Center then added its new GM 1⁄2-ton frame-horn reinforcement kit: a crossbrace with triangulating tubes made from 13⁄4-inch- DOM stock. GM Truck Center says this fix helps control frame torque, which tends to overstress the weak point—behind the steering box. Offroad Design’s Bolt-In Steering Box Brace Kit will also be reinstalled.

Steering Box, Pump
The previous ram-ready box disappeared, but the stock-style pump remains, mounted to the K10’s Ram-Jet 350 crate engine. Going with our “if it ain’t broke” theme, Offroad Design helped fill in the blanks. The company sells PSC-built hydraulic steering components for GM trucks, and it recommended the Economy steering box for this street/trail K10. This particular econo-box begins as a clean-core ’80-’87 Saginaw unit from a 2WD application. The ’80s cores are generally in better shape than the earlier ones, and 2WD versions have the stronger fully splined sector shafts. PSC rebuilds these base boxes with new seals and fresh internal parts as necessary. Because we’re adding a hydraulic ram, we got an assist-ready box tapped with ports in the optimal locations for feeding the ram cylinder. (A hose kit is available with the ram; we’re getting custom hoses with AN-6 fittings from Aeroquip.)

The previous box and pump had the later metric O-ring ports. The jury is hung between these and the earlier inverted-flare fittings. One school (the old one) says that inverted flares are more solid and less likely to leak. The other school answers that if you do spring a leak, it’s likely from a failed O-ring—a cheap, easy fix. Our existing engine-mounted pump/reservoir and the PSC box have metric ports, so we’ll connect them with the later-model OE-spec O-ring–style hoses.

Offroad Design says that the existing stock-style steering pump and reservoir are marginal—the assist cylinder and extra lines ideally call for increased fluid capacity. A PSC pump with remote reservoir would be optimal, but we’ll run what we brung, then upgrade when it dies. (When you’re retaining the OE pump, Watson recommends updating the older bolt-on pulleys to the later, more reliable press-on ones.) Because we’re running moderate tires and adding ram-assist, Offroad Design doesn’t feel that any high-flow tweaks are necessary. Some of the DIY tricks include drilling out the pump’s main fitting to increase flow, increasing pressure with fewer or thinner shims and by grinding the limiting stud, and stretching the spring to maintain the pressure at higher engine rpm. See the sidebar for other, more extreme tricks.

Our previous hydraulic cylinder worked so well that it was adopted for another project. For the rebirth, Offroad Design supplied its base-level PSC cylinder, 13⁄4 inches in diameter. The hydraulic cylinder functions kind of like a 2,000-psi steering stabilizer, effectively doubling the steering force to the tie-rod. Watson says that ram-assist is a nice addition to 35-inch tires and becomes nearly a necessity off-road at 37s and up.

Draglink angles can get hideous following moderate lifts, even with an aftermarket steering arm. To keep the draglink and tie-rod as parallel as possible, Offroad Design offers a two-part solution: crossover-style linkage and a high-steer, on-top-of-the-axle conversion.

The crossover step contours the draglink to work more side-to-side (parallel to the tie-rod) as opposed to the OE front-to-rear steering action. When the frame is twisted off-road, the steering wheel can lose its orientation to the tires in the OE setup. Crossover linkage allows the steering to go full lock-to-lock, regardless of frame twist.

The high-steer step routes the tie-rod over the springs, mounting it to Offroad Design’s billet arms on top of the axle. This increases ground clearance under the tie-rod.

Steering Column, Shaft
The previous ididit column and Borgeson shaft were pirated and replaced by tired factory parts. We will freshen or replace these when we do the interior, using a 3⁄4-inch/30-spline joint between an impact-absorbing shaft and PSC box instead of a rag joint.

At this point we’re basically done from the frame down. Paint could be on tap for next time.

PhotosView Slideshow

Extreme Solid-Axle Chevy Steering
Our steering upgrades are tailored for a mild lift and streetability. Additional steering force is often needed as tires get larger, track width increases, and the Chevy/GMC 4x4 spends more time off-road on tight trails.

Offroad Design’s K5-based truggy Wally runs full-hydraulic steering. Stephen Watson set Wally up with a PSC double-ended 21⁄2-inch-diameter cylinder, a PSC cooler, and a PSC high-flow pump with a remote reservoir. With off-road demands becoming increasingly more extreme, even better equipment is constantly being developed. Offroad Design should have higher-flow-than-ever pumps available by the time this article is printed.

For these scenarios, Offroad Design sells higher stages of steering assist. The foun-dation is PSC Extreme Duty steering boxes, which are built with all-new internals and billet caps and covers. Offroad Design’s hydraulic upgrades also include PSC high-flow pumps, extra-capacity remote steering fluid reservoirs, steering coolers, and a 2-inch-diameter hydraulic cylinder. Additionally, Offroad Design can help integrate PSC ram-assisted steering into a hydroboost brake system.

Beefier linkage is also available. Offroad Design’s standard upgraded crossover draglink and tie-rod used in this article are made from 11⁄4x0.250-wall DOM tubing. Optional are 11⁄2x0.375-wall stock and even built-to-order 2x0.250-wall linkage. All tubing is tapped directly with threads to accommodate beefy tie-rod ends or Heim joints.

Heavy-duty aftermarket knuckles are also available from Offroad Design. These are made from ductile iron and have an extra hole for the steering arms to increase clamping force. Offroad Design’s billet high-steer arms are drilled with an extra hole, so they will work with both OE and heavy-duty aftermarket knuckles. Applications are available for D44/Chevy 10-bolt as well as for D60.

For hardcore off-road-only use, Offroad Design can customize full-hydraulic steering. This system uses a double-ended PSC hydraulic ram, eliminating all of the packaging and geometry challenges imposed by frame-mounting a steering box and routing mechanical linkage. Four-wheel steering is another full-hydraulic option.


Superlift Suspension Systems
West Monroe, LA 71292
Eaton Corporation
GM Truck Center
Burbank, CA 91502

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