General Motors CVT250 (VT40)

General Motors' CVT250 — the belt CVT in the Malibu, the Trailblazer and the small crossovers around them.

⚑ General Motors spent thirty years avoiding the CVT and then adopted one, which is why so little institutional knowledge sits behind it: a technician who has spent a career on 4T65-E and 6T70 automatics has no CVT intuition to bring, and the diagnostic habits from a planetary gearbox do not transfer.

Its health is the belt and the pulleys, and both are decided by fluid. GM specifies its own CVT fluid; DEXRON is not a substitute, and the substitution is behind most reported juddering and slipping.

Simulated shift steps are deliberate. The control strategy imitates a stepped automatic under acceleration because drivers dislike a CVT's flare — so a report of it changes gear strangely is usually describing designed behaviour.

Shudder from rest is the standing complaint and is more often torque-converter lock-up than the variator itself, which is worth establishing before anything expensive is proposed.