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INSTALLATION INSTRUCTION

88554

Rev E

For Rancho Non-Torsion Bar Drop Suspension System

RS6554B:

GM 2500HD.

READ ALL INSTRUCTIONS THOROUGHLY FROM START TO FINISH BEFORE BEGINNING INSTALLATION

IMPORTANT NOTES!

WARNING: This suspension system will enhance the off-road

performance of your vehicle. It will handle differently, both on

and off-road, from a factory equipped passenger car or truck.

Extreme care must be used to prevent loss of control or vehicle

rollover during abrupt maneuvers. Failure to drive this vehicle

safely may result in serious injury or death to the driver and

passengers. ALWAYS WEAR your seat belts, REDUCE your

speed, and AVOID sharp turns and other abrupt maneuvers.

A. Before installing this system, have the vehicle’s alignment

and frame checked by a certified technician. The alignment

must be within factory specifications and the frame of the

vehicle must be sound (no cracks, damage or corrosion).

B. Do not install a body lift kit with this suspension system or

interchange Rancho components with parts from another

manufacturer. New Rancho shock absorbers are required and

must be purchased separately.

Front Rear

RS5380 RS5381

RS7380 RS7381

RS999380 RS999381

C. Do not powder coat or plate any of the components in this

system. To change the appearance of components, automotive

paint can be applied over the original coating.

D. Each hardware kit in this system contains fasteners of high

strength and specific size. Do not mix hardware kits or

substitute a fastener of lesser strength. See bolt identification

table on page 2.

E. Compare the contents of this system with the parts list in

these instructions. If any parts are missing, contact the Rancho

Technical Department at 1-734-384-7804.

F. Install all nuts and bolts with a flat washer. When both SAE

(small OD) and USS (large OD) washers are used in a fastener

assembly, place the USS washer against the slotted hole and

the SAE washer against the round hole.

G. Apply a drop of thread locking compound to all bolts during

installation. CAUTION: Thread locking compound may irritate

sensitive skin. Read warning label on container before use.

H. Unless otherwise specified, tighten all nuts and bolts to the

standard torque specifications shown in the table below. USE

A TORQUE WRENCH for accurate measurements.

Ultra Wheels : 18 x 9

w/ 6” BS

BFGoodrich Mud-Terrain T/A 35 x 12.5 x R18

Summary of content (15 pages)

PAGE 1
INSTALLATION INSTRUCTION 88554 Rev E For Rancho Non-Torsion Bar Drop Suspension System RS6554B: GM 2500HD. READ ALL INSTRUCTIONS THOROUGHLY FROM START TO FINISH BEFORE BEGINNING INSTALLATION Ultra Wheels : 18 x 9 w/ 6” BS BFGoodrich Mud-Terrain T/A 35 x 12.5 x R18 IMPORTANT NOTES! WARNING: This suspension system will enhance the off-road performance of your vehicle. It will handle differently, both on and off-road, from a factory equipped passenger car or truck.
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I. Some of the service procedures require the use of special tools designed for specific procedures. The following tools and supplies are recommended for proper installation of this system: application catalog or contact Rancho Technical Support at 1734-384-7804. If you are installing this system on a 2wd vehicle some of the steps in these instructions may not be applicable (4wd only).
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PARTS LIST # 1 2 3 DESCRIPTION RS6554B-1 Box 1 Of 4 1 RS176613 Box Plate, Weld In 1 RS770239 HHTS, 5/16-18X0.75 2 RS176614 Diff Drop Bracket - Left 1 RS7642 Washer, 5/16 SAE 2 RS176615 Diff Drop Bracket - Right 1 RS860696 Sub Assy, Rear Brake 1 RS176624 E-Brake Relocation 1 RS176625 Rear Brakeline Bracket 1 RS860688 4 Sub Assy, Rear Bump Stop Spacer QTY 1 RS7911 Nut, 12Mm-1.75 Top Lock 5 RS770241 HHCS,M8-1.25X25MM 1 RS7915 Washer, M12 12 RS603112 Nut, 8MM-1.
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16 11 11 14 13 12 10 20 9 20 15 7 8 8 3 7 2 6 5 18 1 19 4 17 4 FRONT SUSPENSION 2) Raise the front of the vehicle and support the frame with jackstands. Remove the front wheels and set them aside. VEHICLE P REPARATION & TORSION B AR REMOVAL 1) Park the vehicle on a level surface. Set the parking brake and chock rear wheels. Measure and record the distance from the center of each wheel to the top of the fender opening. See illustration #1. 3) Mark the torsion bars left and right.
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4) (4wd only) Remove the cap, nut and washer from the hub. Remove the eight bolts from the inboard flange. See illustration #4. Adjuster Adjuster Bolt Torsion Bar Adjustment Arm Illustration #2 6) Repeat steps 4 and 5 for the other side. Illustration #4 7) Remove the torsion bar crossmember by removing the two OE bolts securing it. Make sure to disconnect the O2 sensor wire that is connected to the crossmember.
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3) Remove the brake caliper assembly by loosening the 2 mounting bolts. Hang the caliper assembly with wire or a tie wrap. The brake caliper is very heavy, so be sure to properly support it. F RONT DIFFERENTIAL REMOVAL (4WD ONLY) 4) Label the brake rotor left or right. Remove the brake rotor by removing the one OE bolt fastening it to the hub. 2) Remove the vehicle crossmember that is directly below the differential. Save the OE mounting hardware for reuse later.
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1.00” Line of Cut Mark and Drill Hole Illustration #8 Illustration #10 9) Thoroughly clean the remaining portion of the mount and prep for welding. Weld box plate 176613 to the outside of the pocket. See illustration #9. IMPORTANT!!! Only weld on the outside of the pocket. Welding on the inside will cause interference issues with the subframe. Make sure that all batteries are disconnected before welding.
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4) (4wd only) Reattach left differential drop bracket 176613 to the differential. Reuse OE bolt in the front and middle mount with provided M12-1.75 nut and 1/2” USS washers from hardware kit 860688. Use the M121.75 x 40mm bolt, M12 nut and two M12 washers from kit 860688 for the aft mount. Apply Loctite to OE hardware. Only snug the hardware at this time. 1/2” From End 5) (4wd only) Attach right differential drop bracket 176614 to the vehicle mount using the OE mounting hardware.
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2) Reinstall OE bumpstops into bumpstop spacer 176616 and subframe. Twist bumpstop while pushing up. 176622 Left lower Control Arm 176629 3) Attach left control arm to the subframe using one M18-2.5 x 120mm, two M18 washers and one M18 Nylock nut for the front mount (install from the front) and one M18-2.5 x 150mm, two M18 washers and one M18 Nylock for the rear mount (install from the rear) from hardware kit 860869. Only snugly tighten the hardware at this point.
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4) (4wd only) Secure half shaft to hub using OE washer and center bolt. Place a drift or large screwdriver through the wheel mounting bolts to prevent the drive axle from turning. Torque to 155 ftlbs. 5) 12) Install new sway bar end links from kit 860180. Reuse the four OE end link bushings, which need to be separated from the OE retainers. The end link should be installed from top to bottom, with retainers on the backside of each bushing and the spacer sleeve in the middle. See illustration #19.
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3) Using the hardware from kit 860434, loosely attach the end of the aft brace to the rear of the subframe 176626 using one 1/2-13 x 4.0” bolt, one 1/2-13 stover nut and two 1/2” SAE washers. The aft braces must angel out toward the frame in the rear. Torsion Key Adjuster Adjuster bolt 4) Loosely attach aft brace bracket 176138 to aft brace using one 1/2-13 x 4.0” bolt, one 1/2-13 stover nut and two 1/2” SAE washers. See figure #21.
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9) Torque all 1/2” mounting hardware to 90 ft-lbs 10) Repeat the previous two steps for the other side. will need to be removed from the front wheels. Use sticky wheel weights that attach to the inside diameter of the wheel. 13) Confirm that the tire does not rub on any components or wires. 11) Tighten the aft brace and bracket mounting bolts to 65 ft-lbs. 14) Tighten the lower control arm pivot bolts to 250 ft-lbs. 12) Install front wheels and lower vehicle to ground.
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7) Place bump stop spacer 176620 on the OE bump stop saddle. Using the OE bolt on the aft, attach the OE brake line bracket and spacer bracket. Use the 5/16-18 x .75 self tapping bolt and 5/16 SAE washer from hardware kit 860691 to attach the bracket in front. See illustration #25. 176620 OE Bolt Illustration #23 OE Brake Line Bracket 8) Raise the axle assembly until the riser block contacts the helper spring. Be sure to align the hole in the block with the head of the center bolt.
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11) Attach OE brake line bracket to bracket 176625 using two M8-1.25 x 20 mm bolts, two Nylock nuts and four M8 washers from 860696. See illustration #27 Torque to 23 ft-lbs. Illustration #27 16) Install rear wheels and lower vehicle to ground. Tighten the lug nuts to 140 ft-lbs. OE Bracket M8-1.25 x 20mm 176625 OE Nut FINAL CHECKS & ADJUSTMENTS Check for binding and proper slip yoke insertion.
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www.gorancho.com Rancho Technical Department 1-734-384-7804.