When creating or modifying a transmission model:
For a realistic simulation and to prevent acceleration singularities when torques are applied, connect inertia blocks with nonzero inertia values to gear shafts.
To specify the engaged and free clutches for proper transmission gearing, set up a clutch schedule. Set all clutch pressures to 0 only if you want to disengage the transmission completely, that is, place it in neutral.
Do not engage any more or fewer clutches than necessary, at any time during simulation.
If you redesign a transmission by adding or removing gears, you might also have to:
Add or remove clutches.
Redesign the clutch schedule.
Add or remove gear shaft inertias.
On the relationship clutch pressure signals to solver choices and settings, see Driveline Simulation Performance.