Aisin TB-50LS

Aisin's light rear-drive five-speed — in the Isuzu MU-X and the Suzuki Grand Vitara.

An Isuzu and a Suzuki sharing a gearbox is the kind of connection that only becomes visible once the designation is established, and it roughly doubles the literature for both.

These are working vehicles and heat is what shortens the transmission's life. Towing and low-range use put load through the torque converter, and the fluid pays for it first — which makes an auxiliary cooler a preventative measure rather than an accessory.

Its recurring complaint is a shudder at light throttle, the lock-up clutch rather than the transmission slipping, and it tracks fluid condition closely enough that a service is a diagnostic step.

Where genuine wear appears it is the direct clutch, presenting as a flare on one change under load — and catching it early is the whole difference, because a slipping clutch contaminates the fluid with what it sheds.