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How do I tell an LQ4 from an LQ9?
Check the paperwork, not the seller:
- RPO sticker (glovebox) of the donor: the code LQ9 must be listed.
- VIN 8th digit of the donor: N is the LQ9 code in GM trucks and SUVs (LQ4 = U). The digit meaning varies by platform, so pair it with the RPO.
- Donor vehicle: LQ9s came in the Cadillac Escalade (AWD/2WD/EXT/ESV), Silverado SS and GMC Sierra Denali. A plain Silverado 2500 is usually an LQ4.
Both are 6.0 L iron blocks with the same bore and stroke. The LQ9's extra power comes from higher compression (10.00:1 vs 9.40:1).
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