UMI CarCraft G-Body Rear Suspension Upgrade
G-Body Rear Suspension Overhaul With UMI Performance
The latest installment in the Car Craft build was the get the rear suspension finished. With the front suspension and brakes installed, Jesse moves to the rear by ditching all the factory equipment and upgrading it all in one shot. Watch as he installs a complete UMI Performance suspension system along with a Strange rear and Wilwood brakes.
Project CC Malibu Wagon: Rearend, Suspension & Brakes
Our 1980 Malibu wagon’s tired 7.5-inch 10-bolt makes weak, one-wheel burnouts. It can’t drift, handle well, or make aggressive launches. With plans for a 700hp LS1 stroker, we expect the differential to explode into dust the first time out of the driveway. So to help us stay on the road, we turn to the circle track for inspiration and install race-proven components: a Strange Engineering floater 9-inch, Wilwood 13-inch brakes, and UMI Performance Stage 3.5 suspension.
Brand-loyalty debates aside, Ford got the 9-inch rear axle right. It’s universally accepted at the drag strip and certainly the most common axle in circle track racing. Strange Oval supplies top-tier NASCAR teams with 9-inch rear axles. We called their sister company, Strange Engineering for a Street Floater 9-inch G-body housing (PN: HF9GGME; $839) with an HD Pro center section (PN: P3203BB; $540), and 3:50 gears. Most rearends are built to order, but a kit with mostly the same components retails for $2,685.
While we’re under the car, we’ll finish our UMI Performance Stage 3.5 suspension (PN GBF035-2; $3,799.99) and Wilwood Superlite 4R brakes (PN 140-12435; $2,066.39) with parking brake. Every component of our assembly applies specifically to our goals: be street-able, adjustable, hold 700 hp, improve the handling, and save weight.
The Strange Engineering G-body 9-inch housing features 0.141-inch mild steel, a heavy-duty 0.282-inch thick faceplate with internal gussets, and 3-inch diameter, 0.25-inch wall axle tubes. Inside, Strange Engineering’s 35-spline S-Trac is a torque-biased, mechanical, clutchless Posi-traction unit (PN N1980; $995). It uses helical gears for smooth and progressive power transfer. During a turn, the external force generates friction which slows the spinning tire and sends power to the tire with the most traction. According to Strange, the S-Trac will not interfere with our car’s steering. It’s claimed to be quiet, dependable, and maintenance free with a lifetime breakage warranty. Strange told us the HD Pro 9, 35-spline axles, and S-Trac are some of their most well-rounded products which will handle street, drag, and the road course with ease.
Strange Engineering and Wilwood developed a floater brake package with six different options, ranging from $900 to $2,100. Our Superlite 4R 4-piston caliper, 13-inch drilled, slotted, and Electro-coated rotors pair with our front system, which uses the same rotors and 6-piston calipers.
For our street/road course plans, UMI Performance suggested their Street Performance Monotube shock with 20 rebound settings (PN S131; $229) and 2-inch lower springs, on all four corners. The lower control arms are made from 0.120-inch wall thickness mild-steel tubing, and allow the use of a stock sway bar, something the wagon doesn’t have. The upper, rear control arms feature UMI Roto-Joints for the frame mount, and Moog bushings for the axle side, producing a balanced setup between comfortable and competitive.
UMI’s Roto-Joints allow for 28 degrees of total rotation with no restrictions. They’re designed to keep the suspension traveling up into the wheel wells and prevent it from moving sideways. The rubber in standard bushings will flex, allowing the rear axle to shift side to side. During heavy cornering, banking, or a one-wheel bump, the Roto-Joints work to reduce that lateral movement. It’s possible to run all solid ends on the rear control arms, which would nearly eliminate all lateral movement from the rear axle. UMI offers adjustable rod ends on the lower arms and Roto-Joints on the upper arms. Our combination, with polyurethane lower bushings and Roto-Joint uppers, sacrifices some performance for comfort, as solid joints can be noisier and produce a harsher ride. It’s the porridge that’s just right.
Our conveniences often add complexity, such as adding a parking brake. Luckily, the Wildwood brake kit is relatively simple. It’s essential to test-fit without red Loctite first. We needed to remove the backing plate three times to get the right caliper shims. The caliper needs to be centered on the rotor by changing the shims between the caliper and bracket mounts. We required the addition of a parking-brake cable kit (Wildwood PN 330-9317; $129.54).
