Before you spend a dime with us — or with anyone — try the AFM disabler GM already built into your truck. It's the shifter, and it's free.
⏱ The 10-second version
🚫 Skip the M5 method if:
- Most of your miles are highway — M5 locks out 6th gear, so you cruise at higher RPM and burn more fuel
- You already know you'll forget — it only works if you do it every single drive
- Your lifters are already ticking — nothing that switches AFM off repairs existing damage
- You already run a tune or disabler — this would be doing the same job twice
✅ Worth trying if:
- You want AFM off today, for exactly $0
- You want to test-drive V8-only life before buying anything
- Your driving is mostly town and short trips, where 6th gear barely matters
- Your truck is leased or under warranty and you won't touch the ECM — this is zero hardware, zero software
💡 The whole trick, in one paragraph
Owners across GM forums keep reporting the same pattern: put the transmission in manual / range-select mode, pick M5 or lower, and AFM never activates — the truck stays in V8 the whole drive. Bump it up to M6 and V4 mode comes right back. Two of the cleaner threads on it are here and here.
GM has never documented this behavior, so file it under "strong owner consensus," not gospel. The good news: it takes exactly one drive to verify on your own truck. Steps below.
What "free" actually costs
Effort, every drive. It's a routine, not a setting. Shift to M, tap up to 5, every time you get in. There is no set-and-forget here.
6th gear. When GM shipped trucks with AFM/DFM switched off during the 2021 chip shortage, its own estimate of the penalty was about 1 MPG — and those trucks kept every gear. In M5 you're also giving up overdrive, so expect the highway hit to be bigger than that.
Patience. One Tahoe owner ran the L5 routine for two months, then got tired of it and bought a plug-in disabler — he had an extended warranty, so flashing a tune was off the table. That's not a knock on the method. That's just what month two feels like.
The details
Step-by-step: the M5 method
- Start the truck and pull the shifter to M (on some years it's L plus the +/− buttons — anything that gives you range select).
- Tap + until the dash shows 5.
- Drive normally. Range select is a factory mode: the transmission still shifts itself through gears 1–5. You're not rowing gears, you're capping the top one.
- Verify it: flip your driver display to the screen with the V4/V8 readout (most of these trucks have one) and confirm it stays in V8.
- Repeat every single time you start the truck. That's the method, and that's the catch.
Bonus free method: the Tow/Haul button
One Silverado owner logged a 118-mile trip towing about 3,000 lbs in Tow/Haul and reported zero V4 time the whole way. A single data point, but it fits the pattern: give the truck a real job and AFM steps aside. If you tow regularly, you may already be running "AFM off" more than you think.
What M5 does not do
- It repairs nothing. A lifter that's already noisy stays noisy in M5 — and in every other mode.
- It guarantees nothing. Keeping the truck out of V4 removes one specific stress — the constant lock/unlock cycling on the AFM lifters. Owners are clear that lifters can still fail with AFM off.
- For the hopeful side of the same coin: one owner who switched AFM off with a tune reports 196,000 miles on factory hardware. One truck. Not a promise. But it's the outcome everyone here is chasing.
❓ Quick questions
Is it bad to drive in M5 all the time?
Range select is a factory mode — the same one your owner's manual points you to for towing and long grades. You're using gears the truck already uses, minus the top one. The trade-off owners report is higher cruise RPM and fuel burn, not breakage.
Will this quiet a lifter that's already ticking?
No. A tick means wear has already happened, and no AFM-off method — free or paid — un-wears metal. At that point you're shopping for a diagnosis, not a driving trick.
I have an 8-speed or 10-speed. Does M5 work there?
Honest answer: the reports we can verify are from 6-speed trucks and SUVs. Newer 8- and 10-speeds — especially 2019+ DFM engines — are a different system, and we haven't confirmed the same behavior there. If you want to test it: pick top-gear-minus-one in manual mode and watch whatever cylinder readout your cluster offers. The display doesn't lie.
The lazy version (yes, this is the pitch)
M5 works. It's also homework, every single drive. Our plug-in disabler does the same job — keeps the truck in V8 — without the remembering: plug it in once, and unplug it any time and you're back to stock.
The same honesty applies: it's not a repair, it guarantees nothing, and GM's own math says AFM-off costs about 1 MPG. If the M5 routine suits you — use it and keep your money.
Sources: the forum threads above are individual owner reports, not lab data — they're linked so you can judge them yourself. GM's ~1 MPG figure comes from its 2021 decision to ship trucks with AFM/DFM switched off during the chip shortage, as reported by Autoblog. All links accessed July 2026.
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