2005–2022 Ford Super Duty Adjustable 4-Link Conversion Kit

Installation Guide | Apoc Industries | Fits: 2005–2016 & 2017–2022 Ford F-250/F-350 Super Duty | Stock to 10" Lift

Overview

This guide covers the installation of the Apoc Industries adjustable 4-link conversion kit as an upgrade from the factory radius arm suspension system or an existing 4-link system. The goal of the 4-link conversion is to improve suspension geometry, gain caster adjustment capability, and allow precise axle centering in the fenderwell. This guide assumes the customer is upgrading the front suspension only and is not performing a complete lift installation at the same time.

Pre-Install Checklist

Required Tools

• Floor jack and jack stands
• Torque wrench
• Socket set — metric and standard, 3/8" and 1/2" drive
• Digital angle finder or caster gauge
• Grease gun
• Loctite (recommended for jam nuts)
• Safety glasses, gloves, and steel-toed boots (PPE)

Determine Your Lift Height Before Starting

• Measure your current lift height accurately before beginning — if you have a coil spring lift plus an additional spacer, add both measurements together to get your total lift height
• Use the arm length chart below to set both upper and lower arms to the correct length for your lift height before installation
• Correct arm length is critical for proper axle centering and caster angle

Bushing Grease — Important

⚠ All Apoc Industries polyurethane bushings must be lubricated with silicone grease only. Never use petroleum-based grease on polyurethane bushings — petroleum grease will break down the polyurethane material and cause premature bushing failure.

Safety Warnings

⚠ Always support the vehicle securely on jack stands before working under it. Never rely solely on a floor jack. Keep wheels on the vehicle during this installation to allow easier axle movement.

Arm Length Chart

Set arms to the following center-to-center lengths based on your total lift height. Measure total lift height by adding coil spring lift and any spacer together.

Hardware Torque Reference

Step-by-Step Installation Sequence

Step 1 — Support the Vehicle and Prepare the Axle

• Support the frame at ride height or just slightly higher using jack stands — the vehicle must be stable and level throughout the install
• Leave the wheels on the vehicle — this makes it easier to move the axle during installation
• Place a floor jack under the front differential/pinion with no upward pressure — just enough contact to prevent the axle from rolling forward when the radius arms are removed

Step 2 — Remove the Factory Radius Arms

• Remove one radius arm at a time — do not remove both before having the floor jack in place under the pinion
• Remove both radius arms completely and set the factory radius arm bolts aside — these will be reused
• With both arms removed the axle is now free to be positioned during installation

Step 3 — Install the 4-Link Frame Brackets (Both Sides)

• Slide the APOC 4-link frame bracket up inside the factory radius arm frame bracket on each side — the bracket is designed to nest inside the factory mount
• The factory radius arm bolt (reused) goes through the upper front hole of the factory mount and the corresponding hole in the APOC bracket — this secures the top of the bracket
• Install one of the supplied 3/4" bolts through the lower rearward hole of the factory mount (the original radius arm pivot hole) to hold the bracket in place while you install the control arms
• Hand-tighten only at this stage — do not torque yet
• Repeat on the opposite side

Step 4 — Set Arm Lengths and Install Grease Fittings

• Set both upper and lower 4-link arms to the correct length from the arm length chart above
• Install all grease fittings into the arm ends now, before the arms are installed on the truck — this is much easier with the arms off the vehicle
• Lubricate all polyurethane bushings with silicone grease before installation — do not use petroleum-based grease

Step 5 — Install the Upper 4-Link Arms

• Install the upper arms first — you may need to use the floor jack to roll the axle forward slightly to allow the arms to fit into position
• The axle-side upper arm mount reuses the factory bolts — install and hand-tighten only
• The frame-side upper arm mount uses the factory radius arm bolt (reused) — install and hand-tighten only
• Do not torque yet

Step 6 — Install the Lower 4-Link Arms

• Install the lower arms after the uppers are in place
• The axle-side lower arm mount uses the new alignment cam bolts (supplied) — these allow caster adjustment. Install and hand-tighten only
• The frame-side lower arm mount uses a new supplied 3/4" bolt — install and hand-tighten only
• Do not torque yet

Step 7 — Lower to Ride Height and Verify Axle Position

With all arms installed hand-tight, lower the vehicle to ride height with the full weight of the truck on the wheels before checking anything or torquing any fasteners.

• Check that the coil spring is not making contact with the sway bar end links — if it is, the axle is too far forward. This typically means the lift height measurement was off and the actual lift is less than expected. Recheck your total lift height (coil spring lift + any spacer) and adjust arm lengths accordingly
• Verify the axle appears centered in the fenderwell on both sides — the recommended arm lengths are designed to recenter the axle and eliminate tire rubbing
• Confirm the coil springs are sitting straight and not binding

Step 8 — Torque All Fasteners Except the Alignment Cam Bolts

With the vehicle at ride height and axle position confirmed, torque all hardware except the alignment cam bolts — those are done last after caster is set:

• Factory radius arm bolt (upper front frame bracket hole): 222 ft-lbs
• All new supplied 3/4" bolts (frame bracket and lower arm frame side): 222 ft-lbs
• Jam nuts (all adjustable arm ends): Tighten firmly — apply Loctite to prevent loosening under vibration
• Mark all torqued fasteners with a torque stripe for visual verification

Step 9 — Set and Verify Caster, Then Torque the Alignment Cam Bolts

Caster is the final adjustment. With the vehicle at ride height and all other fasteners torqued:

💡 What is Caster? Caster is the angle of the steering axis — specifically, how far the upper ball joint is behind the lower ball joint when viewed from the side. If you drew a line through the center of the upper and lower ball joints, that line should be tilted rearward 3.5–5 degrees from vertical. Caster is what keeps your truck tracking straight on the road and causes the steering wheel to return to center after a turn. If your truck wanders on the highway or pulls every time it hits a dip in the road, you likely need more caster.

How to Measure Caster:

• Place a digital angle finder on the machined flat surface on top of the steering knuckle, around the upper ball joint — this surface is designed for this measurement
• The reading should be between 3.5 and 5 degrees
• Apoc Industries recommends no less than 3.5 degrees — factory Ford spec is approximately 3.5 degrees
• For trucks running offset wheels, Apoc recommends approximately 5 degrees for best on-road tracking and steering return

Adjusting Caster:

• Use the alignment cam bolts on the lower arm axle-side mount for fine caster adjustment
• If more adjustment range is needed than the cam bolts provide, adjust the lower arm length in or out to reach the desired caster angle, then use the cam bolts for final fine-tuning
• Once caster is set to your preference, torque the alignment cam bolts to 158 ft-lbs

Post-Install Notes

• A professional front-end alignment is strongly recommended after installation to verify caster, camber, and toe settings
• Re-check all fastener torque after 50–100 break-in miles
• Grease all arm end fittings at each oil change interval using a grease gun
• Inspect all hardware for loosening at each oil change interval
• Always use silicone grease on polyurethane bushings — petroleum-based grease will break down the polyurethane and cause premature failure

Safety Disclaimers

This installation guide is provided for reference purposes. Apoc Industries assumes no liability for improper installation, use of incorrect torque values, or failure to follow all safety procedures. Suspension modifications significantly affect vehicle handling characteristics. Always have suspension work inspected by a qualified mechanic and comply with all local laws regarding vehicle modifications and lift height limits.

Apoc Industries | apocindustries.com | Document Version: v1.0