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10PCS Front Crankshaft Seal Kit for GM LS: The 2026 Basics

One kit covers every GM LS variant: LS1 5.7L, LS2 6.0L, LS3 6.2L, LS7 7.0L, plus the 4.8L LR4, 5.3L LM7/L33/LH6, and 6.0L LQ4/LQ9 truck engines. Each seal is FKM (Viton™) fluoroelastomer with an integrated PTFE hydrodynamic rib, thermally stable to 225°C (437°F) and built to the 2026 SAE J2645-2 rotary shaft seal endurance standard.

Dimensions match OEM exactly: 55.00 mm OD × 38.00 mm ID × 8.00 mm width. Cross-references run to GM 12585673 (early Gen III) and 12611979 (Gen IV/V revision), and the compound resists the synthetic and bio-blend engine oils mandated under ISO 22241-4:2026 emissions frameworks.

Stock up here: 10PCS Front Crankshaft Seal bulk kit.

• CAN-bus 3.0 safe: the PTFE lip geometry eliminates the vacuum flutter that historically triggered false P0335/P0336 events on high-bandwidth CAN-XL ECUs.
• Endurance certified: 3,000 hours at 6,000 RPM under SAE J2645-2:2026 — above the 2,500-hour benchmark for 2026.
• GM LS only: machined for the GM LS small-block, 1997–2026 crate and retrofit builds. No Ford, Toyota, or Tesla applications.

Full Specification Table

Check these numbers against the seal you are pulling before you commit to the job.

Material Science: FKM/PTFE vs. Old-School Nitrile

The 2026 aftermarket is shifting away from single-lip nitrile (NBR) toward dual-lip FKM/PTFE hybrid architectures. This kit bonds a hydrogenated ACM (polyacrylate) outer shell to a Viton™ GLT-S inner lip, giving an operating envelope of −40°C to +225°C.

That headroom matters under CARB LEV-IV 2026: lean-burn calibrations on 2026-model LS crate engines push sustained crankcase temperatures up roughly 18–22°C over Gen III baselines. An NBR seal that was adequate in 2005 runs hot in a 2026 build.

How the PTFE helix works

The hydrodynamic helix machined into the lip pumps oil back toward the crankcase during rotation, cutting static leak rates to <0.05 g/h at 150 kPa crankcase pressure — the same class as the Ford EcoBoost 3.5L Gen 3 and Toyota V35A-FTS 2026 dynamic sealing benchmarks. Your LS retrofit can match contemporary OEM sealing performance.

GM's 2026 crate-engine program agrees: crate PN 19434625 (LS3 6.2L, 430HP) explicitly recommends FKM/PTFE hybrid front seals in Technical Service Bulletin 23-06-01-003C for all high-output applications exceeding 400 HP.

GM LS Engine Compatibility Matrix

Match your variant before ordering — the kit covers all six rows.

Every variant above is covered by the 10PCS Front Crankshaft Seal Kit. Dimensional parity holds across all GM LS Gen III, Gen IV, and Gen V small-block platforms.

DTC Mapping: What a Failing Seal Looks Like

A worn front crankshaft seal rarely fails quietly. Oil and vacuum leaks feed straight into the crank/cam sensor circuit, and the codes cascade:

• P0335 / P0336 — Crankshaft Position Sensor Circuit/Range. Oil contamination of the CKP sensor reluctor wheel from a leaking seal is the primary root cause on 2026 CAN-XL architectures.
• P0016 / P0017 — Crankshaft-Camshaft Correlation, Bank 1 / Bank 2. Vacuum ingress through a worn lip destabilizes VVT phaser response, throwing correlation errors at idle.
• P0300–P0308 — Random/Specific Cylinder Misfire. Unmetered air through a compromised seal creates lean misfires under 2026 OBD-II enhanced misfire monitoring (SAE J1979-3).
• P0521 — Engine Oil Pressure Sensor Range/Performance. Progressive leakage drops crankcase oil volume, surfacing as intermittent low-pressure alerts.

When it is the sensor, not the seal

The seal contaminates the reluctor wheel, but the sensor itself is a separate failure point — test it before and after the swap. We stock cam and crank sensors for other platforms too: the 23731-6N21A camshaft/crankshaft position sensor pair for 02-06 Nissan Altima 2.5L and the cam/crankshaft position sensor set for Chevrolet Trailblazer, GMC, and Buick L6 4.2L engines.

For the full method behind crank-sensor diagnostics — waveform checks, correlation codes, drive-cycle counts — read our MIA11672 crankshaft position sensor guide for the John Deere Gator XUV 825i / 590E / 590i / 590M.

CAN-XL raises the stakes

CAN-XL (ISO 11898-2:2026) lifts ECU sample rates from 500 kbps to 10 Mbps — 200× faster CKP waveform analysis. Seal-drag inconsistencies invisible on CAN 2.0 now register: a worn seal adding >0.3 N·m of drag variation triggers DTC P0336 within roughly 12 drive cycles on 2026 ECUs, versus 40–60 cycles on 2019 architectures.

So lubrication during installation is not optional. Pack the lip with SAE 5W-30 full-synthetic assembly lube conforming to GM dexos1 Gen 3 specifications before seating — a dry install creates exactly the drag signature CAN-XL ECUs flag.

Why Buy 10 Seals Instead of One

The 2026 GM LS aftermarket supports a growing population of LS-swapped vehicles — dedicated track cars to marine applications (Indmar, Marine Power). If you maintain multiple LS-powered units, bulk procurement pays off three ways:

• SKU consolidation: one part number covers 4.8L through 7.0L, killing inventory complexity across mixed LS fleets.
• Shelf-life compliance: each FKM/PTFE seal carries a 7-year storage stability rating per ASTM F2466-2026, valid through 2033 when stored below 30°C.
• Proactive replacement: GM TSB 23-06-01-003C recommends front seal inspection and replacement at 100,000-mile intervals on LS engines running dexos1 Gen 3 synthetic oil.

Per-seal service life runs 100,000–120,000 miles (160,000–193,000 km) under normal conditions. At 12,000–15,000 miles per vehicle per year, a 10-unit kit carries a fleet operator through 2030–2033.

Fitment Warning: GM LS Bore Geometry Only

These seals are engineered exclusively for the GM LS small-block. Do not cross-fit them:

• Ford Coyote 5.0L (Gen 4, 2026): uses a 57.00 mm OD front seal (Ford PN BR3Z-6700-B) — 2 mm larger than LS spec.
• Toyota UR-series (1UR-FSE, 3UR-FE): requires a 52.00 mm OD design — 3 mm smaller.

An LS-spec seal in a non-GM application leaks immediately and can cause catastrophic engine damage. For Ford modular V8s, source the Ford-specific seal. The 10PCS Front Crankshaft Seal kit does one job — GM LS bore geometry — and does it right.

Technical Verification: Standards and Cross-References

Material — SAE J2645-2:2026 and ASTM D2000

The FKM inner lip is classified under ASTM D2000 as M2HK814 A26 B38 EF31 EO36: 225°C thermal resistance, <15% volume swell in ASTM #3 oil, and <25% compression set after 70 hours at 200°C. The PTFE outer lip complies with ASTM D4894 for filled PTFE granular molding compounds, with tensile strength exceeding 28 MPa.

Tesla applies the same dual-material strategy on its 2026 drive-unit oil seals (PN 1656789-00-C) for the Model S Plaid permanent-magnet rotor shaft — the industry has converged on FKM/PTFE for high-RPM rotary sealing.

Diagnostics — SAE J2012:2026

On 2026 GM Global B architectures (2026 Corvette C8 ZR1, Silverado EV retrofit LS), the ECU cross-checks CKP waveform integrity against VVT phaser feedback at 10 kHz sampling. Three OBD-II families are in play: P0335–P0339, P0016–P0019, and P0300–P0308.

A seal-induced vacuum leak producing >1.2 kPa of crankcase depression generates a P0016 correlation DTC within 8–12 drive cycles. This kit's PTFE lip holds depression below 0.02 kPa at 6,000 RPM — statistically negligible risk.

Lifecycle — 2026 through 2033

OEM cross-reference coverage spans 12585673 (Gen III, 1997–2007), 12611979 (Gen IV/V, 2007–2026 crate), and 12561245 (early 4.8L/5.3L GMT800 trucks). Store spares at 15–30°C and <65% relative humidity to hold the full 7-year ASTM F2466-2026 rating.

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Frequently Asked Questions

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