UMI Performance 78-88 GM G-Body Rear Control Arm Reinforcement Braces - Black

Bolt-In Rear Control Arm Mount Reinforcement Braces for the 1978-1988 GM G-Body

The factory rear control arm mounts are the known weak point on a G-Body chassis. Under a hard launch the sheet metal around the upper and lower mounts flexes, and on a car with tubular arms and polyurethane bushings that flex simply moves further up the structure. This pair of braces ties the upper and lower mount on each side into one triangulated unit.

UMI calls the part Control Arm Reinforcements and Frame Braces, and its own installation sheet titles it a tubular frame brace. Each brace is DOM steel, TIG welded and pre-bent to follow the contour of the floor, so nothing has to be dented or hammered flat, and the threaded adjuster with jam nuts lets the same part fit the build variation across every G-Body body style.

Key Features

• Ties the rear upper and lower control arm mounts together into a triangulated structure on each side.
• DOM steel construction, TIG welded.
• Pre-bent to contour the floor pan, so UMI states no denting or pounding of the floor is required.
• Length-adjustable with jam nuts, so one part fits the variation across all G-Body body styles.
• Longer Grade 8 bolts, lock nuts and washers are supplied in the box.
• Bolt-in installation using the existing rear control arm bolt locations, two new bolts per side.
• Natural companion to any rear control arm upgrade, since the same eight bolts are already coming out.
• Black powder coat.

Fitment

UMI publishes these braces for the full 1978-1988 GM G-Body vehicle list. UMI publishes year, make and model only for this part number and lists no submodel or trim breakdown, so the fitment tags on this listing stop at model rather than inventing a trim.

Exhaust clearance warning, in UMI's own words: they may reduce muffler clearance, as they add distance to the inside lower attachment point, so take care when ordering if you have large mufflers. This is the only exhaust conflict UMI publishes on any part in this family, and it is worth measuring before you buy if the car runs oversized mufflers.

One further installation note from UMI's sheet: the parking brake cable routed above the rear end bump stop may need to be loosened to get the brace into position.

Specifications

What's Included

• Two bent DOM steel braces, one per side, in black powder coat, each with a threaded adjuster and jam nuts
• Longer Grade 8 mounting bolts, two per side
• Lock nuts
• Washers
• Installation instruction sheet

That is the complete documented contents. UMI records no grease packet and no sticker with this part. A retailer independently describes the same item as tubular frame braces with hardware, which agrees with UMI's own list.

About UMI Performance

UMI Performance builds chassis and suspension parts at 509 Hemlock Street in Philipsburg, Pennsylvania, using North American raw material from USA steel suppliers, machine-guided precision DOM tube bending, laser-cut plating and welds laid by skilled and robotic welders. Chassis stiffening for the G-Body is a small part of the catalogue but a well documented one, and this brace is the piece UMI recommends alongside its rear control arm kits because both jobs share the same four bolts per side.

Related Parts

• UMI 301516-B non-adjustable tubular rear control arm kit for 1978-1988 GM G-Body
• UMI 301417-R adjustable rear control arm kit for 1978-1988 GM G-Body

FAQ

That is the one clearance question UMI itself flags. Its published note is that the braces may reduce muffler clearance, because they add distance to the inside lower attachment point, and to take care when ordering if you have large mufflers. Measure the space inboard of the lower control arm mount before ordering if the car runs oversized or aftermarket mufflers.

None of those. UMI bends the braces to contour the floor specifically so that no denting or pounding of the floor is required, and the installation is a bolt-in using the existing control arm bolt locations with the longer supplied bolts.

Yes. UMI supplies longer Grade 8 bolts, lock nuts and washers, and the installation sheet uses two of those new longer bolts per side. Unlike UMI's rear control arm kits, you do not need to source anything to install these.

UMI's sheet is explicit: torque all control arm bolts to 72 ft-lb, and torque them with the suspension fully loaded to prevent suspension bind, then tighten both jam nuts on the braces. Do not carry over the 90 ft-lb value printed on UMI's 4029 A-Body brace sheet, which is a different part on a different platform.

Yes, that is the whole design. Each brace picks up the upper control arm bolt and the lower control arm bolt on the same side and triangulates between them, which is why the sheet has you loosen all eight control arm bolts before starting.

Yes, and that is the most common pairing. The braces mount to the same control arm bolts a tubular arm uses, so builders usually fit them at the same time as a rear control arm kit while the fasteners are already out.

Possibly. UMI's sheet notes that the e-brake cable routed above the rear end bump stop may need to be loosened to get the brace into place. It is a minor step, but it is worth knowing before the car is in the air.

Yes. UMI's published vehicle list for this part covers the full G-Body range, including the El Camino and the GMC Caballero, and the adjustable length is specifically there to absorb the variation between body styles.

Install the brace on the upper bolt first, with the adjustment end closer to the lower control arm bolt and the adjusting nut oriented toward the upper control arm. Extend the adjuster until the brace picks up the lower bolt without forcing the chassis, then lock both jam nuts once the control arm bolts are torqued at full suspension load.

UMI publishes no sway bar conflict for this part, and the brace runs between the control arm mounts rather than across the sway bar path. The clearance UMI does warn about is muffler clearance at the inside lower attachment point.

As a pair, one brace per side, with the hardware for both sides in the same box.

UMI publishes a two year warranty from the original date of purchase against defects in materials and workmanship, to the original purchaser only, and it is not transferable. The same policy excludes misuse, exceeding the design limits of the product, improper installation, altered product, non-UMI components, incidental costs such as towing and labour, and normal wear items including bearings and bushings. UMI also states it cannot guarantee compatibility with other manufacturers' components. Note that the printed sheet in the box still carries an older, narrower disclaimer that predates the current two year term. The policy page is the current document. Neither is a Black Ops Auto Works warranty.

Installation Instructions

1. Jack the rear of the car and support the frame on two jack stands so the rear end hangs freely.
2. Loosen, but do not remove, all eight rear control arm bolts.
3. Work one side of the car at a time.
4. Remove and replace two bolts on that side with the new longer supplied bolts, leaving roughly one inch of thread protruding.
5. Install the brace on the upper bolt first, with the adjustment end closer to the lower control arm bolt and the adjusting nut oriented toward the upper control arm.
6. Loosen the parking brake cable routed above the rear end bump stop if it interferes with the brace.
7. Extend the adjuster so the brace picks up the lower control arm bolt, then fit the supplied lock nuts and washers.
8. Repeat the process on the opposite side.
9. Load the suspension fully, then torque all control arm bolts to UMI's published 72 ft-lb to prevent suspension bind.
10. Tighten both jam nuts on the braces and re-check the fasteners after the first drive.

The 72 ft-lb figure and the one inch thread protrusion are UMI's own published values for part 3028. The higher figure printed on UMI's 4029 A-Body brace sheet must not be substituted.