ReadyLIFT SKU 66-3921 Decision file B Choose vehicle to check fitment

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ReadyLIFT 66-3921 1.75 inch GM AT4 and Trail Boss leveling kit

Name: ReadyLIFT 66-3921 1.75 inch GM AT4 and Trail Boss leveling kit
Brand: ReadyLIFT
SKU: 66-3921

Is the ReadyLIFT 66-3921 1.75 inch GM AT4 and Trail Boss leveling kit the leveling kits pick here, or just one of three?

Best fit for Silverado Trail Boss and Sierra AT4 shoppers who need a leveling kit designed around factory-lift geometry.

Put it next to the Rough Country leveling and lift kit and the ReadyLIFT SST leveling and lift kit and the ReadyLIFT 66-3921 1.75 inch GM AT4 and Trail Boss leveling kit leads for one kind of buyer while giving ground elsewhere. None of the three is the automatic answer, so read the package, fitment, and install rows before you read the price.

Reviewed by Nicole

Editor

Fitment

2019-2026 Silverado 1500 Trail Boss, excluding ZR2

Verify first

Use on Silverado 1500 Trail Boss factory-lift trucks when the current ReadyLIFT or seller fitment tool confirms the exact year, cab, drive, and trim. The product is not a normal-height Silverado spacer kit.

Part number: 66-3921
Choose it when: Best fit for Silverado Trail Boss and Sierra AT4 shoppers who need a leveling kit designed around factory-lift geometry.
Pass when: It stops being the right call the moment this holds: Silverado ZR2

Our cross-product compare

Same category. Different reason to buy.

Evidence level B

Decision point

Current decision file ReadyLIFT 66-3921 1.75 inch GM AT4 and Trail Boss leveling kit Part 66-3921 Rough Country Rough Country leveling and lift kit ReadyLIFT ReadyLIFT SST leveling and lift kit

Best for

A factory-lift GM 1500 leveling kit for Trail Boss and AT4 trucks that need control-arm and strut-spacer geometry built around the OEM 2 inch lift.

A broad Rough Country suspension family for truck owners comparing front levels, loaded struts, and mild lift kits after exact trim and suspension-package checks.

A ReadyLIFT SST family for shoppers who want vehicle-specific spacer, control-arm, or mild lift packages with official application and warranty checks.

What's included

Front lift: 1.75 inches · Install type: Top and bottom strut spacers with tubular upper control arms

Coverage type: Truck lift-kit product family

Exact contents depend on the SST leveling and lift kit SKU you select for your truck.

Product approach

Do not substitute normal-height GM 1500 spacer or loaded-strut products on Trail Boss/AT4 routes without exact product confirmation.

Prefer Walmart and eBay when exact identity and seller terms are comparable.

Documented fitment only -- no standout approach beyond exact application is recorded for the SST leveling and lift kit.

Install burden

Moderate install. Exact 66-3921 SKU and UPC 804879610489

Moderate install. exact Rough Country SKU

Moderate install. exact ReadyLIFT SKU

Fitment

Confirm the exact ReadyLIFT 66-3921 1.75 inch GM AT4 and Trail Boss leveling kit application for Chevrolet Silverado 1500 Trail Boss factory-lift trucks before ordering.

Confirm the exact Rough Country leveling and lift kit application for Ram 1500 SLT Quad Cab 4x4 before ordering.

Confirm the exact ReadyLIFT SST leveling and lift kit application for Ram 1500 SLT Quad Cab 4x4 before ordering.

Choose it when

Pick the 66-3921 1.75 inch GM AT4 and Trail Boss leveling kit over the Rough Country leveling and lift kit and the ReadyLIFT SST leveling and lift kit when you want an OE-grade replacement with the widest dealer and parts-store availability.

Choose the leveling and lift kit when it is the exact match for your truck and the ReadyLIFT 66-3921 1.75 inch GM AT4 and Trail Boss leveling kit and the ReadyLIFT SST leveling and lift kit do not list your application.

Choose the SST leveling and lift kit when it is the exact match for your truck and the ReadyLIFT 66-3921 1.75 inch GM AT4 and Trail Boss leveling kit and the Rough Country leveling and lift kit do not list your application.

Current decision file

ReadyLIFT 66-3921 1.75 inch GM AT4 and Trail Boss leveling kit

Part 66-3921

Best for: A factory-lift GM 1500 leveling kit for Trail Boss and AT4 trucks that need control-arm and strut-spacer geometry built around the OEM 2 inch lift.
What's included: Front lift: 1.75 inches · Install type: Top and bottom strut spacers with tubular upper control arms
Product approach: Do not substitute normal-height GM 1500 spacer or loaded-strut products on Trail Boss/AT4 routes without exact product confirmation.
Install burden: Moderate install. Exact 66-3921 SKU and UPC 804879610489
Fitment: Confirm the exact ReadyLIFT 66-3921 1.75 inch GM AT4 and Trail Boss leveling kit application for Chevrolet Silverado 1500 Trail Boss factory-lift trucks before ordering.
Choose it when: Pick the 66-3921 1.75 inch GM AT4 and Trail Boss leveling kit over the Rough Country leveling and lift kit and the ReadyLIFT SST leveling and lift kit when you want an OE-grade replacement with the widest dealer and parts-store availability.

In the boxDrawn to explain, not a product photo.

Leveling kits owned fitment checklist visual — Illustration

Where to buy it

Seller offers

Each seller on its own terms - prices and stock reflect the date shown with each seller and can change; the seller's checkout price is final.

Paid link

Amazon

Worth a look when the exact part number is sold direct, but confirm the seller of record before you order.

Price, availability, seller details, ratings, and reviews are shown only on Amazon.

As an Amazon Associate I earn from qualifying purchases.

Available at Amazon

Seller checked Seller link

eBay Motors

New-in-box listings from national parts sellers cycle through here, so let the individual listing set condition and returns rather than trusting the category.

In stock - Stock checked Aug 6 - verify at seller before checkout - Price updated Aug 6, 2026

Price and stock were current at the last check.

$529.95 View seller price

Other retailers to check

These other-retailer searches use the brand and part number shown on this page. We earn nothing if you buy through them.

Other retailer

Summit Racing

House fitment data and manufacturer spec sheets ride along on their pages, which makes it a good spot to sanity-check the part number.

Search with the brand and part number shown on this page, then confirm the manufacturer part number before ordering.

Search Summit Racing

Other retailer

Walmart

A broad marketplace where third-party sellers vary widely, so check who is actually selling and how returns work.

Search with the brand and part number shown on this page, then verify the exact seller, item condition, fitment, and return terms.

Search Walmart

The current best price is at its recent low across 2 price checks. The seller's checkout page has the final say; make sure stock, exact SKU, and seller details all agree before you order.

Report an issue

Decision trail Check these before you buy.

Part ReadyLIFT 66-3921 1.75 inch GM AT4 and Trail Boss leveling kit Part 66-3921. ReadyLIFT resource available.

Fits 2019-2026 Chevrolet Silverado 1500 Trail Boss factory-lift trucks Use on Silverado 1500 Trail Boss factory-lift trucks when the current ReadyLIFT or seller fitment tool confirms the exact year, cab, drive, and trim. The product is not a normal-height Silverado spacer kit.

Watch for Leveling Kits checkout checks Confirm suspension package, air-suspension exclusions, alignment plan, tire clearance, brake-line routing, and warranty impact before checkout.

Other retailer · Seller eBay Motors at $529.95 In stock. Stock checked Aug 6 - verify at seller before checkout. Compare return terms before leaving Fitment Pilot.

Photos Category visual The photo shows the category, not this exact part; an exact product photo appears once image rights are confirmed.

If unsure Compare, read, or report If the seller page, vehicle details, or photos do not line up, compare sellers, read the guide, or report the issue.

The evidence

Fitment and install resources

Reviewed 2026-06-25

Official product page ReadyLIFT 66-3921 product page ReadyLIFT Install instructions ReadyLIFT 66-3921 installation instructions ReadyLIFT Install video ReadyLIFT 66-3921 Silverado install video ReadyLIFT and installer video context

Editorial method

What we checked on this page

We check the ReadyLIFT 66-3921 1.75 inch GM AT4 and Trail Boss leveling kit for exact part identity, seller options, stock and price dates, photo rights, and official resources.

Sellers4 seller destinations

Paid offers and other retailer searches are labeled separately so you can choose where to check.

FreshnessStock checked Aug 6 - verify at seller before checkout

Stock and price freshness are shown with each seller before checkout.

PhotosCategory visual only

This photo shows the part category, not this exact product. Confirm SKU, size, and kit contents before ordering.

Resources3 official resources

Install, fitment, spec, or warranty resources are available before checkout.

An exact product photo appears here once image rights are confirmed.

Under the listing

Choose it, pass, or verify

A factory-lift GM 1500 leveling kit for Trail Boss and AT4 trucks that need control-arm and strut-spacer geometry built around the OEM 2 inch lift.

Choose it if

Best fit for Silverado Trail Boss and Sierra AT4 shoppers who need a leveling kit designed around factory-lift geometry.
Do not substitute normal-height GM 1500 spacer or loaded-strut products on Trail Boss/AT4 routes without exact product confirmation.
Compare Walmart, eBay, ReadyLIFT direct, and specialty sellers while refreshing seller stock, return terms, and exact SKU before checkout.
Use on Silverado 1500 Trail Boss factory-lift trucks when the current ReadyLIFT or seller fitment tool confirms the exact year, cab, drive, and trim. The product is not a normal-height Silverado spacer kit.

Pass if

The ReadyLIFT 66-3921 1.75 inch GM AT4 and Trail Boss leveling kit is not the right choice when your truck falls outside 2019-2026 Chevrolet Silverado 1500 Trail Boss factory-lift trucks, or its trim, engine, and package cannot be matched to the documented application.
Pass when this exclusion applies: Silverado ZR2
Choose another kit when the truck needs more height, rear-load support, adjustable damping, or hardware this package does not include.

Verify

Exact 66-3921 SKU and UPC 804879610489
Trail Boss trim and current seller fitment tool
Wheel/tire test fit, CV boot care, alignment, headlamp aim, ADAS calibration, and 500-mile recheck
The checked public route is a 2024 LT Trail Boss 4x4 Crew Cab. Custom Trail Boss, other cabs, older overlapping body styles, dealer-lift trucks, aftermarket lifts, and ZR2 need current seller and installer checks before inheriting this answer.