Belt CVT (continuously variable)

The architecture, for the cars whose specification says only CVT and names no unit. The maker-specific pages in this catalogue — Jatco's, Aisin's, Subaru's, Toyota's — carry the part numbers; this one carries what they all share.

A belt CVT has two variable-width pulleys and a steel push-belt between them, and the ratio changes because the pulleys close and open. The whole drive depends on hydraulic pressure clamping those pulleys onto the belt — there is no clutch pack holding a gear, no synchro, and nothing mechanical that stays engaged on its own.

That single fact orders every symptom. The failure sequence is the same on every belt CVT ever built:

1. Aged fluid loses clamping pressure before it loses anything else. Felt as a slip under acceleration — the engine rises and the car does not — most obviously uphill or overtaking.
2. The pulley faces glaze where the belt has been slipping against them.
3. The belt marks them permanently, and at that point the unit is replaced rather than repaired.

The first stage is a fluid service and the last is a new transmission, which is why CVT fluid intervals are real in a way that a torque-converter automatic's are not. The fluid is not a generic ATF and is not interchangeable between makers — Nissan's NS-2/NS-3, Toyota's CVT-FE, Subaru's CVTF, Honda's HCF-2 are different fluids for different clamping systems.

A shudder at light throttle at a steady speed is usually the torque converter's lock-up clutch, not the belt — most CVTs have one — and that distinction is worth making before anything expensive is contemplated.

Towing, sustained hills and stop-start traffic age the fluid far faster than the odometer suggests.

Three different things are called a CVT in a specification and only one of them is this. A hybrid e-CVT is a planetary power split with two motors and no belt at all; an electric car's single-speed reduction is a fixed gear with no ratio to vary. Neither can have any of the faults above, and both have their own pages here.