01-31-2021, 12:14 PM
Hi Pete,
I have a 12 speed ZF in my#1218 2008 coach, on the back of a C15 625.
The ZF transmission is exactly like a normal constant mesh manual gearbox, if yours's is a AS Tronic, it has a normal clutch IE friction plate and pressure plate.
Clutch actuation and gear selection are automatic, that is controlled by the gearbox Control unit, which is linked to the engine controller and brake system.
My 12 speed box is the same unit as yours with an addition of a half gear split on each of the 3 main gears.
Like any auto box if you apply a small amount of throttle whilst driving the gearbox controller will alter the change points automatically conversely accelerate with full throttle it will hold the gears longer before it changes, off the throttle down hills it will change down, a quirk with the 12 speed is that it will not select 12th until 60mph, if you manually select on the control panel it goes back to 11th after a few moments, this is standard ZF.
Oil level is exactly like a manual truck box to check and make sure it has the correct ZF approved lube not Auto trans fluid, and as you say both the clutch actuator and the gear changes are air pneumatically operated by the gearbox controller.
The 12 speed preselects 3 to start off, but you have to manually select 2nd or 1st if required if maneuvering ( this saves the clutch).
Another common issue is the clutch actuators go faulty and strangely do not fully disengage when out of gear and idling, this makes the clutch smell, just like it is or has been slipping, over here in the UK the ZF AS tronic is very popular so well supported, a ZF tech can plug into the coach and read all the stored parameters, tell you clutch wear % over temps (clutch) not box and over torque.
My coach has like a hill start function, lets say you are stationary on a hill facing upwards in slow traffic when you come off the footbrake there is a delay before the brakes release, this gives you time to apply the throttle without rolling back (that's why the box controller is linked to the brake system) once moving it all works like a full auto although it is not seamless like an Allison.
When you 1st start up with low air you will get the key pad flashing letter codes these clear once the air is built up.
Regards
Ian
I have a 12 speed ZF in my#1218 2008 coach, on the back of a C15 625.
The ZF transmission is exactly like a normal constant mesh manual gearbox, if yours's is a AS Tronic, it has a normal clutch IE friction plate and pressure plate.
Clutch actuation and gear selection are automatic, that is controlled by the gearbox Control unit, which is linked to the engine controller and brake system.
My 12 speed box is the same unit as yours with an addition of a half gear split on each of the 3 main gears.
Like any auto box if you apply a small amount of throttle whilst driving the gearbox controller will alter the change points automatically conversely accelerate with full throttle it will hold the gears longer before it changes, off the throttle down hills it will change down, a quirk with the 12 speed is that it will not select 12th until 60mph, if you manually select on the control panel it goes back to 11th after a few moments, this is standard ZF.
Oil level is exactly like a manual truck box to check and make sure it has the correct ZF approved lube not Auto trans fluid, and as you say both the clutch actuator and the gear changes are air pneumatically operated by the gearbox controller.
The 12 speed preselects 3 to start off, but you have to manually select 2nd or 1st if required if maneuvering ( this saves the clutch).
Another common issue is the clutch actuators go faulty and strangely do not fully disengage when out of gear and idling, this makes the clutch smell, just like it is or has been slipping, over here in the UK the ZF AS tronic is very popular so well supported, a ZF tech can plug into the coach and read all the stored parameters, tell you clutch wear % over temps (clutch) not box and over torque.
My coach has like a hill start function, lets say you are stationary on a hill facing upwards in slow traffic when you come off the footbrake there is a delay before the brakes release, this gives you time to apply the throttle without rolling back (that's why the box controller is linked to the brake system) once moving it all works like a full auto although it is not seamless like an Allison.
When you 1st start up with low air you will get the key pad flashing letter codes these clear once the air is built up.
Regards
Ian
#1218 in Europe based in the UK