1967-1981 Camaro Firebird Trans Am 3/4-Inch or 1-Inch Rear Leaf Spring Lowering Block Set, UMI-2621

Hawks Motorsports is proud to offer our clients this : 1967-1981 Chevrolet Camaro, Pontiac Firebird, Formula and Trans Am Rear Leaf-Spring Lowering Block Set from UMI Performance.

UMI Performance #2621 allows owners to lower the rear of a compatible leaf-spring-equipped Camaro or Firebird an additional 3/4 inch or 1 inch, helping fine-tune the vehicle’s stance without replacing the existing rear leaf springs.

Two lowering-height options are available:

• UMI-2621-1: 3/4-inch rear lowering blocks
• UMI-2621-2: 1-inch rear lowering blocks

Each set features satin-black 6061-T6 aluminum lowering blocks with factory-compatible locating pins. Heavy-duty U-bolts, matching washers and nuts are supplied for installation.

The lowering blocks install between the rear leaf springs and the axle spring perches. This moves the rear axle upward relative to the body, lowering the vehicle by approximately the thickness of the selected block.

UMI-2621 is compatible with UMI Performance #2620 rear leaf springs and most other stock-location leaf springs using the compatible factory-style mounting arrangement. The blocks may be used with original GM multi-leaf springs, compatible replacement springs and properly configured aftermarket rear leaf springs.

UMI originally promoted this kit primarily for 1970-1981 second-generation Camaro and Firebird models. The manufacturer’s current detailed fitment guide now also lists 1967-1969 first-generation Camaro and Firebird applications, providing verified 1967-1981 GM F-body coverage.

The kit is particularly useful for Pontiac Firebird and Trans Am applications where the taller, more rounded rear wheel opening can create the visual impression that the rear of the vehicle sits higher than a similarly lowered Camaro. UMI developed and tested the lowering-block package on its 1973 Firebird to help achieve a more balanced front-to-rear stance.

Actual lowering can vary slightly because of existing leaf-spring condition, spring sag, vehicle weight, fuel load, wheel and tire size, spring rate, bushing condition and previous suspension modifications.

Available Lowering Options

UMI-2621-1: 3/4-Inch Lowering

The 3/4-inch version provides a moderate rear ride-height adjustment. It is a suitable choice when the vehicle needs a subtle stance correction or when additional tire, exhaust, shock and bump-stop clearance is desired compared with the 1-inch option.

• Block thickness: 3/4 inch
• Approximate additional rear lowering: 3/4 inch
• Manufacturer part number: 2621-1
• Hawks Motorsports variant SKU: UMI-2621-1

UMI-2621-2: 1-Inch Lowering

The 1-inch version provides the maximum lowering offered in the UMI-2621 series. It is suitable for vehicles requiring a more noticeable rear stance adjustment while retaining the existing compatible leaf springs.

• Block thickness: 1 inch
• Approximate additional rear lowering: 1 inch
• Manufacturer part number: 2621-2
• Hawks Motorsports variant SKU: UMI-2621-2

Set Contents

The UMI-2621 package includes:

• Two 6061-T6 aluminum rear lowering blocks
• Factory-compatible locating-pin configuration
• Heavy-duty extended U-bolts
• Matching U-bolt washers
• Matching U-bolt nuts
• Satin-black finish
• Components for the driver and passenger sides
• Customer-selected 3/4-inch or 1-inch block height

Compatible Rear Leaf Springs

UMI-2621 is designed for:

• UMI Performance #2620 rear leaf springs
• Original GM rear multi-leaf springs
• Factory-style replacement rear leaf springs
• Compatible stock-location performance leaf springs
• Standard-style axle-over-leaf mounting arrangements
• Compatible Camaro rear leaf springs
• Compatible Firebird rear leaf springs
• Compatible Formula rear leaf springs
• Compatible Trans Am rear leaf springs

Always confirm the spring width, axle-perch arrangement, locating-pin engagement and U-bolt fit before installation, particularly when the vehicle has a non-original rear axle or custom suspension components.

Important Product Information

UMI-2621 is a rear lowering-block set. It is not:

• A complete rear leaf-spring set
• A rear leaf-spring bushing kit
• A rear shackle kit
• A front leaf-spring mounting-pocket kit
• A rear shock absorber kit
• A rear sway-bar kit
• A traction-bar kit
• An axle relocation kit
• A rear coil-spring spacer
• A lift block
• A pinion-angle correction wedge
• A universal truck lowering-block kit
• A replacement rear axle spring perch

The UMI-2621 blocks are flat lowering blocks. Vehicles requiring pinion-angle correction may need a separately selected driveline-angle solution after the actual operating angles are measured.

4. KEY FEATURES

• Fits manufacturer-verified 1967-1981 GM F-body applications
• Fits applicable first-generation Chevrolet Camaro models
• Fits applicable second-generation Chevrolet Camaro models
• Fits applicable first-generation Pontiac Firebird models
• Fits applicable second-generation Pontiac Firebird models
• Fits applicable Pontiac Firebird Esprit models
• Fits applicable Pontiac Firebird Formula models
• Fits applicable Pontiac Firebird Trans Am models
• Fits applicable Turbo Trans Am models
• Lowers the rear approximately 3/4 inch or 1 inch
• Two selectable lowering heights
• UMI-2621-1 provides approximately 3/4-inch lowering
• UMI-2621-2 provides approximately 1-inch lowering
• Allows fine-tuning of rear ride height
• Helps create a more level front-to-rear stance
• Useful for correcting the visual rear-wheel-opening height on Firebird models
• Installs between the rear leaf spring and axle spring perch
• Compatible with UMI Performance #2620 leaf springs
• Compatible with most properly configured stock-location leaf springs
• Compatible with original GM multi-leaf springs
• Compatible with factory-style replacement rear leaf springs
• Compatible with properly configured aftermarket leaf springs
• Manufactured from 6061-T6 aluminum
• Satin-black finish
• UMI’s current specifications classify the finish as anodized
• Factory-compatible locating-pin configuration
• Locating pins help center the axle perches over the leaf springs
• Includes heavy-duty extended U-bolts
• Includes matching washers and nuts
• Supplied as a complete left-and-right set
• Direct bolt-on configuration for compatible applications
• No permanent vehicle modifications required for verified stock-style applications
• Does not require replacing properly functioning compatible leaf springs
• Suitable for restoration and performance vehicles
• Suitable for street-driven vehicles
• Suitable for Pro-Touring builds
• Suitable for autocross vehicles
• Suitable for road-course-inspired builds
• Suitable for compatible show vehicles
• Suitable for correcting excess rear rake
• Suitable for fine-tuning ride height after installing lowering springs
• Suitable for vehicles already equipped with UMI #2620 rear leaf springs
• Proven on UMI Performance’s 1973 Pontiac Firebird
• Manufactured in the USA
• Not a lift-block set
• Not a pinion-angle wedge
• Not designed for rear coil-spring suspension
• Not designed for third- or fourth-generation F-body models
• Not designed for trucks or other universal leaf-spring applications
• Actual ride-height change may vary with vehicle and spring condition
• One set services both sides of the rear axle
• UMI Performance base part #2621
• UMI Performance 3/4-inch part #2621-1
• UMI Performance 1-inch part #2621-2
• Hawks Motorsports base part #UMI-2621

5. MODEL INTERCHANGE AND FITMENT

UMI Performance’s current detailed catalog lists UMI-2621 for 1967-1969 and 1970-1981 Chevrolet Camaro and Pontiac Firebird F-body platforms.

Fitment depends on the rear axle, leaf-spring width, axle-perch design, locating-pin arrangement and standard-style leaf-spring mounting configuration. Engine size, transmission type, brake configuration and trim package do not normally change fitment when the vehicle retains compatible rear suspension dimensions.

Chevrolet Camaro Applications

• 1967 Chevrolet Camaro
• 1968 Chevrolet Camaro
• 1969 Chevrolet Camaro
• 1970 Chevrolet Camaro
• 1971 Chevrolet Camaro
• 1972 Chevrolet Camaro
• 1973 Chevrolet Camaro
• 1974 Chevrolet Camaro
• 1975 Chevrolet Camaro
• 1976 Chevrolet Camaro
• 1977 Chevrolet Camaro
• 1978 Chevrolet Camaro
• 1979 Chevrolet Camaro
• 1980 Chevrolet Camaro
• 1981 Chevrolet Camaro

Includes applicable:

• Camaro Base
• Camaro Sport Coupe
• Camaro Convertible, 1967-1969
• Camaro Rally Sport
• Camaro RS
• Camaro Super Sport
• Camaro SS
• Camaro Type LT
• Camaro LT
• Camaro Berlinetta
• Camaro Z/28
• Camaro Z28
• Factory appearance and performance packages retaining the compatible rear leaf-spring mounting arrangement

Camaro Trim-Year Notes

• Convertible applications are limited to the 1967-1969 first-generation Camaro.
• Rally Sport and RS applications include applicable 1967-1973 models.
• Super Sport and SS applications include applicable 1967-1972 models.
• Type LT applications include applicable 1973-1978 models.
• Berlinetta applications include applicable 1979-1981 models.
• Z/28 and Z28 applications include 1967-1974 and 1977-1981 models.
• The Camaro Z28 was not offered for the 1975 or 1976 model years.
• Trim level does not normally affect fitment when the compatible factory-style rear leaf-spring arrangement is retained.

Pontiac Firebird Applications

• 1967 Pontiac Firebird
• 1968 Pontiac Firebird
• 1969 Pontiac Firebird
• 1970 Pontiac Firebird
• 1971 Pontiac Firebird
• 1972 Pontiac Firebird
• 1973 Pontiac Firebird
• 1974 Pontiac Firebird
• 1975 Pontiac Firebird
• 1976 Pontiac Firebird
• 1977 Pontiac Firebird
• 1978 Pontiac Firebird
• 1979 Pontiac Firebird
• 1980 Pontiac Firebird
• 1981 Pontiac Firebird

Includes applicable:

• Firebird Base
• Firebird Convertible, 1967-1969
• Firebird Sprint
• Firebird 326
• Firebird 350
• Firebird 400
• Firebird Esprit
• Firebird Formula
• Firebird Trans Am
• Turbo Trans Am
• Trans Am Special Edition
• Factory appearance and performance packages retaining the compatible rear leaf-spring mounting arrangement

Firebird Trim-Year Notes

• Convertible applications are limited to the 1967-1969 first-generation Firebird.
• Firebird Sprint, 326, 350 and 400 designations apply to applicable first-generation models.
• Firebird Esprit and Formula applications begin with the 1970 model year.
• Trans Am fitment applies to the 1969-1981 model years.
• Turbo Trans Am fitment applies to applicable 1980-1981 models.
• Trim and engine packages do not normally change lowering-block fitment when the compatible rear leaf-spring arrangement is retained.

Important Fitment Notes

• UMI-2621 is designed for leaf-spring-equipped GM F-body models.
• The rear axle must use an axle-over-leaf mounting arrangement compatible with the supplied blocks and U-bolts.
• The lowering block installs between the upper surface of the leaf spring and the axle spring perch.
• The leaf-spring center pin must properly engage the block.
• The block’s locating pin must properly engage the axle spring perch.
• Both locating points must fully seat before the U-bolts are tightened.
• The lowering blocks must be installed as a matched left-and-right pair.
• Select only one lowering height for the complete vehicle.
• Do not mix a 3/4-inch block on one side with a 1-inch block on the other side.
• UMI-2621-1 provides approximately 3/4-inch additional rear lowering.
• UMI-2621-2 provides approximately 1-inch additional rear lowering.
• Actual ride-height change can vary because of spring condition and vehicle weight.
• Confirm rear tire-to-quarter-panel clearance before selecting a lowering height.
• Confirm tire-to-inner-wheelhouse clearance throughout suspension travel.
• Confirm rear shock compression and extension travel.
• Confirm bump-stop clearance.
• Confirm exhaust-system clearance.
• Confirm brake-hose and parking-brake-cable clearance.
• Confirm driveshaft, pinion-yoke and floor clearance.
• Confirm rear sway-bar and traction-device clearance.
• Measure the existing ride height before ordering.
• Measure both sides from consistent body or wheel-opening reference points.
• Sagged, damaged or mismatched leaf springs should be corrected before using lowering blocks to compensate for an uneven vehicle.
• A non-original rear axle may have different spring perches or axle-tube dimensions.
• Modified spring perches may prevent direct installation.
• Mini-tub conversions, relocated leaf springs and custom rear suspensions require separate compatibility verification.
• Aftermarket shock-relocation systems may change available clearance.
• Vehicles converted to four-link, torque-arm or rear coilover suspension are not compatible.
• UMI-2621 is not intended for 1982-2002 third- or fourth-generation F-body rear suspension systems.
• This kit is not intended for GM X-body applications unless UMI separately confirms the specific vehicle and suspension arrangement.
• Measure driveline operating angles after installation, particularly on vehicles with modified ride height, drivetrain position or rear axle mounting.

6. INSTALLATION NOTES

• Review the applicable GM service manual and UMI Performance instructions before installation.
• Verify the selected block height before beginning installation.
• Measure and record the vehicle’s original rear ride height on a level surface.
• Confirm that both rear leaf springs are in serviceable condition.
• Inspect the leaf springs for cracks, broken leaves, corrosion, spreading, damaged center pins or excessive sag.
• Inspect the front spring mounts, rear shackles and bushings before installation.
• Inspect the axle spring perches for cracks, corrosion, distortion or damaged locating holes.
• Confirm that the vehicle has the compatible axle-over-leaf mounting arrangement.
• Park the vehicle on a solid, level surface.
• Chock the front wheels.
• Safely raise and support the vehicle using properly rated lifting equipment.
• Support the vehicle by approved body or frame locations so the rear axle can be moved independently.
• Support the rear axle with a properly rated hydraulic jack.
• Never work beneath a vehicle supported only by a hydraulic jack.
• Relieve tension from the rear shocks and sway bar only as required by the applicable service procedure.
• Keep the brake hose, brake lines and parking-brake cables from being stretched as the axle is lowered.
• Work carefully to prevent the axle from rotating or shifting.
• Remove the original U-bolt nuts evenly.
• Lower the axle only far enough to create the clearance required for the blocks.
• Do not allow the axle to hang from the brake hose.
• Clean the leaf-spring mounting surface and axle spring perch.
• Remove rust scale, dirt and debris that could prevent the block from seating flat.
• Inspect the leaf-spring center pin for damage or looseness.
• Replace a damaged spring center pin before installing the lowering blocks.
• Position each block between the leaf spring and axle perch.
• Make certain the spring center pin fully engages the bottom locating hole in the block.
• Make certain the block’s upper locating pin fully engages the axle spring perch.
• Confirm that the block sits flat and does not rock or bind.
• Confirm that both blocks face the correct direction.
• Use the same block height on both sides.
• Raise the axle carefully while maintaining locating-pin engagement.
• Install the supplied heavy-duty U-bolts, washers and nuts.
• Verify that each U-bolt sits squarely around the axle tube.
• Verify that the U-bolts do not contact brake lines, vent lines or welded brackets.
• Tighten the U-bolt nuts gradually and evenly.
• Use an alternating cross-pattern to draw the axle plate down uniformly.
• Do not fully tighten one U-bolt before the others are seated.
• Confirm equal thread engagement on the paired U-bolts.
• Do not use an impact wrench for final tightening unless specifically permitted by UMI.
• Follow UMI Performance or the applicable GM service manual for final torque requirements.
• UMI does not publish a universal U-bolt torque specification on the current UMI-2621 product page.
• Do not select a torque value solely from the apparent U-bolt diameter.
• Reconnect the shocks and rear sway bar using the applicable service procedure.
• Confirm that the shocks retain adequate compression and extension travel.
• Confirm that the rear axle does not contact the bump stops prematurely.
• Lower the vehicle onto the ground carefully.
• Roll the vehicle forward and backward to allow the suspension to settle.
• Re-measure the rear ride height at the original reference points.
• Inspect tire clearance with the vehicle at normal ride height.
• Inspect clearance with passengers, fuel and expected cargo loads considered.
• Check driveshaft and pinion-yoke clearance.
• Measure driveline operating angles if vibration develops or the drivetrain has been modified.
• Inspect for axle wrap or wheel hop during controlled initial testing.
• Recheck U-bolt tightness after the initial suspension-settling period and road test.
• Periodically inspect the blocks, locating pins, U-bolts, spring plates and axle perches as part of normal suspension maintenance.