{"product_id":"readylift-1-75-leveling-kit-uca-at4-trail-boss-2019-66-3921","title":"ReadyLIFT 1.75\" Leveling Kit with UCAs | 2019–2025 GMC Sierra AT4 \u0026 Chevy Silverado Trail Boss","description":"\u003cp\u003e\u003cstrong\u003eReadyLIFT 1.75\" Leveling Kit with UCAs | 2019–2025 GMC Sierra AT4 \u0026amp; Chevy Silverado Trail Boss\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eIs This for You?\u003c\/strong\u003e\u003cbr\u003eYou're running a 2019–2025 GMC Sierra 1500 AT4 or Chevy Silverado 1500 Trail Boss — trucks that come from the factory with a 2\" front lift and longer strut assemblies — and every generic leveling kit on the market either binds the factory ball joint or contacts the lower strut and CV axle assembly. You need a leveling kit engineered specifically for the AT4 and Trail Boss platform that works with the factory suspension lift, not against it. The ReadyLIFT 66-3921 delivers 1.75\" of additional front leveling lift with CNC-machined billet aluminum strut spacers and DOM steel UCAs with corrected geometry — purpose-built for this platform.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eThe Result\u003c\/strong\u003e\u003cbr\u003eCNC-machined aircraft-grade billet aluminum top and bottom mount strut spacers deliver 1.75\" of front leveling lift that works in concert with the factory 2\" lift — providing the required amount of lift without conflicting with factory strut geometry or clearances. Heavy-duty DOM tube steel upper control arms with corrected ball joint cup angles, 1-ton heavy-duty replaceable ball joints, and ReadyLIFT TCT (Terrain Control Technology) maintenance-free pivot bushings with side-biter washers restore proper suspension geometry and improve alignment retention at the new ride height. Trail Boss trucks clear a 295\/65R20 on a 20x9 0-offset wheel; AT4 trucks clear a 275\/60R20 on the same spec — fender opening design differs between the two models.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eVerified Fitment (OFAS Standard)\u003c\/strong\u003e\u003cbr\u003e✅ Fits: 2019–2025 GMC Sierra 1500 AT4\u003cbr\u003e✅ Fits: 2019–2025 Chevrolet Silverado 1500 Trail Boss\u003cbr\u003e❌ Does NOT fit: GMC Sierra 1500 AT4X\u003cbr\u003e❌ Does NOT fit: Chevrolet Silverado 1500 ZR2\u003cbr\u003e❌ Note: AT4 and Trail Boss have different front fender opening designs — maximum tire size differs between the two models; test fit before finalizing tire selection\u003c\/p\u003e\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eSpec\u003c\/th\u003e\n\u003cth\u003eDetail\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eLift Height Added\u003c\/td\u003e\n\u003ctd\u003e1.75\" (additional, works with factory 2\" lift)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFront Strut Spacers\u003c\/td\u003e\n\u003ctd\u003eCNC-machined aircraft-grade billet aluminum top and bottom mount strut spacers\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eUCAs\u003c\/td\u003e\n\u003ctd\u003eDOM tube steel, corrected ball joint cup angles, 1-ton HD replaceable ball joints, TCT maintenance-free pivot bushings with side-biter washers\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSKU\u003c\/td\u003e\n\u003ctd\u003e66-3921\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eManufacturer\u003c\/td\u003e\n\u003ctd\u003eReadyLIFT\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\u003cp\u003e\u003cstrong\u003eWheel \u0026amp; Tire Fitment\u003c\/strong\u003e\u003c\/p\u003e\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eApplication\u003c\/th\u003e\n\u003cth\u003eMax Tire\u003c\/th\u003e\n\u003cth\u003eWheel\u003c\/th\u003e\n\u003cth\u003eNotes\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eChevy Silverado Trail Boss\u003c\/td\u003e\n\u003ctd\u003e295\/65R20\u003c\/td\u003e\n\u003ctd\u003e20x9 0 offset\u003c\/td\u003e\n\u003ctd\u003eNo trimming required\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eChevy Silverado Trail Boss (factory wheels)\u003c\/td\u003e\n\u003ctd\u003e285\/75R18\u003c\/td\u003e\n\u003ctd\u003eFactory 18\" wheels\u003c\/td\u003e\n\u003ctd\u003eWheel spacers required\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eGMC Sierra AT4\u003c\/td\u003e\n\u003ctd\u003e275\/60R20\u003c\/td\u003e\n\u003ctd\u003e20x9 0 offset\u003c\/td\u003e\n\u003ctd\u003eNo trimming required\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\u003cp\u003eAT4 and Trail Boss have different front fender opening designs — do not assume the same tire size fits both models. ReadyLIFT wheel and tire fitment recommendations are based on Wheel Pros wheels and Nitto tires. Actual dimensions vary meaningfully by manufacturer — overall diameter, tread width, aspect ratio, and sidewall construction will differ. Every tire and wheel combination must be test fit prior to final installation. Upgrading to heavier 10-ply (Load Range E) all-terrain or mud-terrain tires will noticeably increase suspension stiffness and alter ride harshness compared to factory 6-ply (Load Range C) tires. Consult your local installer for application-specific guidance.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eInstallation \u0026amp; Engineering Notes\u003c\/strong\u003e\u003cbr\u003eThis is a bolt-on leveling kit requiring no cutting or welding. UCA hardware must be torqued to specification at ride height. A professional 4-wheel alignment is mandatory post-installation to verify torque specs and lock in corrected geometry. Lifting your vehicle raises its center of gravity; exercise appropriate caution on- and off-road. All Advanced Driver Assistance Systems (ADAS) including GM Safety Alert Seat, Lane Keep Assist, Forward Collision Alert, and automatic headlight leveling must be checked and recalibrated after installation.\u003c\/p\u003e\u003cblockquote\u003e\n\u003cstrong\u003eEngineering Question:\u003c\/strong\u003e Is your truck a GMC Sierra AT4 or Chevy Silverado Trail Boss, and what is your model year? AT4 and Trail Boss have different fender opening sizes that affect maximum tire fitment — confirm your specific trim before selecting your tire and wheel combination.\u003c\/blockquote\u003e","brand":"ReadyLIFT Suspension","offers":[{"title":"Default Title","offer_id":51631847801153,"sku":"66-3921","price":529.95,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0974\/1284\/1793\/files\/66-3921.jpg?v=1776292362","url":"https:\/\/obsidianforgedautosupply.com\/products\/readylift-1-75-leveling-kit-uca-at4-trail-boss-2019-66-3921","provider":"Obsidian Forged Auto Supply","version":"1.0","type":"link"}