MB6 ✓ Factory-verified

Chevrolet · Regular Production Option

Transmission, Allison A2700PTS, 6 speed automatic, close-ratio, double overdrive, non-conforming school bus or shuttle bus

Years 2025–26 Models 1 Factory citations 2

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Documented applications

Silverado Medium Duty (GM515, 2019–2026) →

• 2025–2026 ✓ Factory-verified

  gear ratios 3.10, 1.80, 1.40, 1.00, 0.70 and 0.61; 26,001 lb GCW maximum (the list prints 26,001K); requires PTX and a park pawl; for GVW above 19.5K

  ⛭ GM factory document — 2025 chevrolet silverado 4500 hd 5500 hd and 6500 hd fleet order guide rpo codes, p.1.

  ⛭ GM factory document — 2026 chevrolet silverado 4500 hd 5500 hd and 6500 hd fleet order guide rpo codes, p.1.

Related codes · mentioned in these notes

PTX

This page aggregates every documented appearance of MB6 in the Chevrolet reference. Confidence and citations are shown per application — the same code can be better documented in one year than another.