ReadyLIFT 4.0-Inch Flat Rear Block Kit | OEM-Style Fabricated Steel | Billet Driveline Spacer + Long E-Coated U-Bolts | 2-Piece Driveshaft Only | 2017–2026 Ford F-250 Super Duty 4WD | SKU: 66-2741

Verified Fitment

Does NOT fit:

• 2019–2026 Ford F-350 Super Duty — explicitly excluded per ReadyLIFT's product documentation; the 2019+ F-350 geometry is not confirmed for this block; see ReadyLIFT's F-350-specific block options
• 1-piece driveshaft applications — this kit includes a billet driveline spacer engineered for the 2-piece driveshaft geometry; 1-piece driveshaft trucks require a different rear block kit
• Ford F-250 Super Duty 2WD — 4WD only
• 2016 and earlier Ford F-250 Super Duty — different rear suspension and U-bolt geometry; see ReadyLIFT's pre-2017 block options
• F-350 DRW (Dually) trucks — the included U-bolts are not sized for dually axle configurations; custom longer U-bolts would be required; confirm before ordering
• Trucks with aftermarket or factory add-on air spring/load leveling kits attached to the bump stop tangs — see critical compatibility note

Factory block variability — net lift may differ: Net lift height gained from this kit will vary based on whether your F-250 came from the factory with an existing rear block installed. Trucks with a factory block already present will gain less net height than stock-height trucks. Measure your factory rear axle-to-frame height before ordering to confirm expected net gain.

Component Specifications

Why fabricated steel — not extrusions: ReadyLIFT explicitly calls this out in their product language: these blocks are "based on OEM designs and never made out of lightweight extrusions." Extruded aluminum or lightweight cast blocks deform under the cyclic loading of a working pickup truck's leaf spring pack. Fabricated steel at the block dimensions required for a 4-inch lift is the OEM-appropriate construction approach — the same material and method Ford uses for the factory block this kit replaces or supplements.

Why the billet driveline spacer matters: At 4 inches of rear block height, the rear axle moves downward relative to the driveshaft — changing the operating angle at the rear U-joint and carrier bearing on 2-piece driveshaft trucks. An uncorrected driveline angle at this block height causes vibration at highway speed and accelerates U-joint and carrier bearing wear. The included billet spacer repositions the carrier bearing to restore correct driveshaft operating angles.

Integrated bump stop landing pads: The bump stop is the rubber cushion that limits maximum suspension compression travel. The OEM bump stop attaches to the frame at a specific height relative to the axle. When the axle drops 4 inches with a block installed, the bump stop geometry changes — the axle hits the bump stop earlier in its travel without the integrated landing pads. ReadyLIFT's integrated pad design accounts for the new geometry and maintains OEM-comparable bump stop function at the lifted height.

What Is and Is NOT Included

Critical Compatibility

The 2-piece driveshaft requirement is not optional. The billet driveline spacer in this kit is engineered for the carrier bearing geometry of the 2-piece driveshaft found on most 4WD Super Duty configurations. Trucks with a 1-piece driveshaft do not have a carrier bearing — the driveline spacer has no mounting point, and the geometry of this block kit is not validated for the 1-piece driveshaft's U-joint angles at 4 inches of rear block height.

To confirm your driveshaft type: Look under the truck at the rear driveshaft. A 2-piece driveshaft has a carrier bearing mounted to the frame crossmember midway along the shaft length — you'll see a bearing with a rubber mount bracket attached to the frame. A 1-piece driveshaft is a single tube running from the transfer case output to the rear axle with no intermediate support.

Air spring/load leveling kit exclusion — structural integrity concern. ReadyLIFT's explicit language: "Use of this type of air bag system will void all block warranties and can cause failure of the block bump stop tang." Air spring systems that mount to the bump stop tangs exert upward load on the bump stop tang when pressurized — a load the tang is not designed to carry in this configuration. Failure of the tang under air spring load is a structural block failure. Do not use this kit with any air spring or load leveling system attached to the bump stop tangs, regardless of brand.

F-350 2019+ exclusion — not a minor fitment note. ReadyLIFT's own source documentation explicitly says "Not for use on 2019–2026 F350." The 2019 Super Duty generation brought changes to the F-350 rear axle and spring configuration that make this block geometry incompatible. If you have a 2019+ F-350, do not order this kit.

Installation Notes

Skill level: Beginner to intermediate — bolt-on rear block replacement. No cutting or welding required. A floor jack, jack stands rated for the vehicle weight, and basic hand tools are sufficient. Professional installation recommended for U-bolt torque sequencing.

Tools required: Floor jack and rated stands, basic socket set, torque wrench (required for U-bolt torque to specification).

Driveshaft confirmation — do before installation day: Before scheduling installation, confirm your driveshaft type. Look for the carrier bearing midway along the rear driveshaft. If present, you have a 2-piece driveshaft — proceed. If no carrier bearing, stop and contact OFAS before ordering.

Installation sequence:

1. Safely lift and support the vehicle with the rear axle at full droop.
2. Remove factory U-bolts and lower the rear axle.
3. Remove the factory rear block (if present).
4. Install the billet driveline spacer at the carrier bearing location per ReadyLIFT's installation instructions.
5. Position the ReadyLIFT flat rear block between the axle perch and the leaf spring at both driver and passenger sides.
6. Install the long e-coated U-bolts and thread Grade 10 nuts.
7. Lower the axle to ride height.
8. Torque U-bolts to OEM specification at ride height — do not torque with the axle at full droop. Final torque must be applied with the suspension at normal ride height and the vehicle weight on the rear axle.
9. Verify carrier bearing alignment and spacer positioning.

Post-installation mandatory steps:

1. Re-torque U-bolts after 500 miles — new blocks will settle slightly under load; re-check torque at the first service opportunity.
2. Alignment verification — recommended after any rear height change.
3. Headlamp aim adjustment — required per ReadyLIFT installation advisory.
4. ADAS verification — check and adjust any ADAS system.

Common Questions

How do I know if my F-250 has a 2-piece driveshaft?
Look under the truck at the rear driveshaft. A 2-piece driveshaft has a carrier bearing mount — a bearing bracket attached to a frame crossmember roughly halfway along the driveshaft. If you see this bracket, you have a 2-piece driveshaft and this kit fits. If the shaft runs as a single tube from the transfer case to the rear axle with no intermediate mount, you have a 1-piece driveshaft and this kit does not fit.

Why doesn't this fit my 2019+ F-350?
ReadyLIFT explicitly excludes the 2019+ F-350 from this kit's confirmed fitment. The 2019 Super Duty generation included F-350-specific changes to the rear axle and spring geometry that make this block incompatible. ReadyLIFT offers F-350-specific rear block solutions.

My F-250 already has a factory rear block — what lift will I actually get?
Net lift gained will be less than 4 inches. ReadyLIFT explicitly notes that final lift height varies based on the factory block your truck has installed. If your F-250 came with a factory block (many do for towing applications), the net gain over the existing block height depends on the difference between the factory block height and this kit's 4-inch block. Measure your current axle-to-frame height before ordering to confirm expected outcome.

Can I use this block with my air bag suspension helper kit?
No — and this is explicitly prohibited by ReadyLIFT. Air spring and load leveling systems that attach to the bump stop tangs put upward structural load on the tang — a load it is not designed to carry in this configuration. ReadyLIFT states this will void the warranty and can cause bump stop tang failure. Do not combine this block with any air bag or load leveling system.

Do I need new U-bolts?
Yes — they're included. The 4-inch block requires longer U-bolts than the factory units. The kit includes four long e-coated U-bolts with Grade 10 nuts and washers — everything needed for a complete installation.

The Obsidian Take

The 66-2741 is a purpose-built component solution for two specific needs: putting rake back in a work truck that's sagging from payload use, and completing the rear lift on a 2017–2026 F-250 that already has a front leveling kit installed. ReadyLIFT positions these blocks as the ideal tow package companion — whether the truck is at stock height or already running a leveling kit.

The fabricated steel construction is the product. Extruded aluminum blocks at 4 inches of height under a loaded Super Duty are a compromise in construction material. ReadyLIFT's explicit language — "never made out of lightweight extrusions" — is there because they know that's the corner competitors cut at lower price points. OEM-style fabricated steel at the block geometry, integrated bump stop landing pads, and billet driveline spacer is the complete engineering package for this application.

The air bag exclusion is the most important advisory on this page for any owner who has installed or is considering installing a load-leveling helper kit. The bump stop tang is a structural element of the block — it is designed to absorb downward axle travel, not upward air pressure. This is not a compatibility preference — it's a structural design limit.

The 2-piece driveshaft requirement and the driveline spacer tell the engineering story clearly: ReadyLIFT built a solution for the specific driveshaft geometry of the 4WD F-250. The spacer corrects the carrier bearing angle that 4 inches of rear block height introduces. That's not universal — it's platform-specific engineering.

This SKU is for: 2017–2026 Ford F-250 Super Duty 4WD owners with confirmed 2-piece driveshaft who want 4 inches of rear block lift to restore towing rake, pair with an existing leveling kit, or achieve a leveled lifted stance all the way around — without air bag systems attached to the bump stop tangs.

This SKU is NOT for: F-350 owners (2019+ explicitly excluded — different block required), 1-piece driveshaft F-250 trucks, F-250 2WD trucks, DRW/dually configurations without custom U-bolts, anyone running air spring or load leveling systems attached to the bump stop tangs, or 2016 and earlier Super Duty owners (different platform — different block required).

SAE J2492 Warning
⚠ WARNING: By installing this product, you acknowledge that the suspension of this vehicle has been modified. As a result, this vehicle may handle differently than factory-equipped vehicles. As with any vehicle, extreme care must be used to prevent loss of control or rollover during sharp turns or abrupt maneuvers. Always wear seat belts, and drive safely, recognizing that reduced speeds and specialized driving techniques may be required. Failure to drive this vehicle safely may result in serious injury or death. Do not drive this vehicle unless you are familiar with its unique handling characteristics and are confident of your ability to maintain control under all driving conditions.

Manufacturer Data Disclaimer
Product specifications, fitment data, and feature details are sourced from ReadyLIFT manufacturer documentation and verified third-party technical references current at the time of publication. ReadyLIFT reserves the right to modify product specifications without notice. Confirm 4WD drivetrain, 2-piece driveshaft, F-350 exclusion, and air bag system compatibility before ordering. OFAS is not responsible for incompatibility resulting from 1-piece driveshaft applications, 2019+ F-350 applications, DRW configurations, or bump stop tang failure resulting from air spring system use.

Prop 65 Warning
⚠ WARNING: This product can expose you to chemicals including lead and lead compounds, which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information, go to www.p65warnings.ca.gov.

Non-Returnable Notice
This item is non-returnable once installed. Verify 4WD drivetrain, 2-piece driveshaft, and air bag system status before ordering. Questions before ordering? Text (469) 407-7538.