UMI Performance 78-88 GM G-Body 1in Solid Chrome Moly Rear Sway Bar - Black

One Inch Solid Chrome Moly Rear Anti-Roll Bar for the 1978-1988 GM G-Body, in Gloss Black

A G-Body leans on its outside rear tire and pushes wide, and the factory rear bar is not big enough to change that. This is a one inch solid 4140 chrome moly replacement that bolts into the exact factory location on the rear end housing and shifts roll stiffness rearward, so the chassis feels balanced instead of nose heavy.

It is hot formed and heat treated as one piece, which UMI says gives twice the tensile and yield strength of a cold bent bar. That process leaves the bar with a slightly textured surface under the powder coat, and UMI publishes that as expected rather than as a flaw. On a drag-biased car the same bar helps keep the body level and straight off the line.

Key Features

• 1.000 inch solid bar in 4140 chrome moly steel.
• Heat treated and hot formed as a single piece.
• UMI states twice the tensile and yield strength of a competitor's cold bent bar.
• Bolts into the exact factory location with no additional parts required.
• Grade 8 described hardware supplied: four M10 bolts, eight M10 washers and four M10 locknuts.
• Works with factory trailing arms and with UMI tubular rear control arms.
• Gloss black powder coat.

Fitment

UMI publishes this bar 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.

Rear axle requirement, and the single most important filter on this part: the bar bolts to the factory rear end housing brackets. UMI's product page states it does not fit a Ford 9 inch rear, and UMI's Stage 3 kit page states more generally that the bar is designed to fit factory rear end housings only, with aftermarket rear ends requiring a chassis mounted bar such as UMI's 3044. Those two statements are consistent, and the broader one is the rule to buy on: factory housing only.

Specifications

What's Included

• One 1.000 inch solid 4140 chrome moly rear sway bar in gloss black powder coat
• Four M10 bolts
• Eight M10 washers
• Four M10 locknuts
• One installation instruction sheet

That is the complete contents. No grease packet, bushings or end links are supplied, because this bar mounts solid to the factory rear end housing brackets rather than through isolators.

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. Its sway bars are the clearest example of process choice in the catalogue: the rear bar is hot formed and heat treated, the front bar is CNC bent, and the company states outright that it will not sell a cold bent bar for this rear application.

Related Parts

• UMI 3035-B 1.250 inch solid front sway bar for 1978-1988 GM G-Body
• UMI 303534-B solid front and rear sway bar kit for 1978-1988 GM G-Body

FAQ

No. UMI's fitment note says it does not fit a Ford 9 inch rear, and its Stage 3 kit page states the bar is designed for factory rear end housings only. The bar bolts to brackets on the factory housing, so any swapped rear end needs a chassis mounted bar instead, which is UMI's 3044.

Downward. UMI's sheet is explicit that the bow should face downward to clear the differential housing. Installing it the other way up is the most common error on this part.

UMI publishes 45 ft-lb if you are using a torque wrench, or moderately tight if you are using normal hand tools. Do the final tightening with the rear suspension in its normal operating position.

Hardware is included. The sheet itemises four M10 bolts, eight M10 washers and four M10 locknuts, and the bar bolts into the exact factory location with no additional parts required.

Yes. UMI states the bar works with both factory trailing arms and UMI trailing arms. Its own non-adjustable and adjustable G-Body rear control arm kits carry reinforced sway bar provision in the lower arms for exactly this reason.

Because it is hot formed. UMI states that a hot formed unit is expected to exhibit some degree of surface texture, and it presents that as an engineering trade-off: the heat treated bar has twice the tensile and yield strength of a cold bent bar, and UMI will not offer a cold bent bar for this application because of premature failure. The texture is a process characteristic, not a defect.

Enough to change the balance of the car. Moving to a one inch solid chrome moly bar at the rear increases rear roll stiffness, which reduces body roll and trims the understeer a stock G-Body carries. UMI does not publish a rate figure for the bar, so no stiffness percentage is claimed here.

Most builders do, because changing only one end shifts the balance rather than simply adding grip. UMI sells the matching 1.250 inch solid front bar and packages the two together as a front and rear kit, which is the straightforward way to keep the balance intentional.

No. An anti-roll bar resists body roll between the two sides of the axle and carries no static load at ride height, so it does not change ride height or spring rate in a straight line.

UMI publishes no exhaust or driveshaft conflict for this bar, and it mounts in the factory location with the bow facing down and away from the differential. That said, on a car with a custom exhaust routed over the axle, check clearance through the full range of suspension travel before the first drive.

No. This bar mounts solid to the factory rear end housing brackets, and no bushings or end links are listed in the kit or required by the procedure.

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. Gather a wrench and socket set, a three ton floor jack and two jack stands.
2. Place the jack under the differential housing and raise the rear of the car, then support it on stands.
3. Remove the old sway bar, using penetrating oil on seized fasteners if needed.
4. Offer the new bar up with the bow facing downward so it clears the differential housing.
5. Insert the supplied M10 bolts from the outside toward the inside.
6. Fit the flat washers and locknuts and tighten in stages rather than one fastener at a time.
7. Torque to 45 ft-lb if using a torque wrench, or moderately tight if using normal hand tools, which is UMI's published wording.
8. Carry out final tightening with the rear suspension in its normal operating position.
9. Lower the car and take a short test drive, then re-check the fasteners.

45 ft-lb is UMI's own published figure for this bar. Do not carry over torque values from UMI sheets for other part numbers, and note the sheet's single reference to a 4034 is a copy-paste artifact from the A-Body sibling part.