[rwg200]

Hi fellow Gurus,

I have a problem with my gearbox or electrics possibly?

I jumped into the coach and fired up and went to put in gear, the pad was displaying SM (system malfunction) i have the 12 speed ZF. The coach goes into gear ok but when i try to pull away the revs hardly build and the coach judders but won't move off, as if the clutch isn't engaging.

I have had a local shop look into it and so far have had the gearbox sent away for inspection, it had a new ECU and valve block fitted, the clutch is in perfect order as well, everything has been refitted and the problem is still there, the coach is supplying air fine and the actuator has also been replaced. approx $7000 spent and no further forward!!
 has anyone experienced these symptoms?

thanks
Rob

[Richard]

Don't know anything about ZF transmissions, but your comment doesn't build any revs is interesting. Check the interfaces between the engine and transmission. Why is the engine not revving? Will the engine rev in neutral?

[Guy]

Is it possible to engage this transmission with the brakes locked up?

[Fulltiming]

Have you checked for an error code? https://www.scribd.com/doc/137329279/ZF-...rror-Codes

[rwg200]

Don't know anything about ZF transmissions, but your comment doesn't build any revs is interesting.  Check the interfaces between the engine and transmission. Why is the engine not revving? Will the engine rev in neutral?

Yep the engine revs cleanly in neutral, its like something is holding it back electronically when in gear, the clutch just starts to engage then the revs drop and it disengages the clutch.

---

Have you checked for an error code? https://www.scribd.com/doc/137329279/ZF-...rror-Codes

Hi Michael,
Yep the code is 78 which interestingly is not on the chart! however i have found something on the internet that talks about the screen filter on the actuator, (the actuator has been replaced) it also talks about a stuck clutch fork but again this has been removed inspected and replaced. im at a total loss!
cheers
Rob

[rwg200]

Is it possible to engage this transmission with the brakes locked up?

The brakes are free as the coach rolls fine, in order to engage a gear the parking brake has to be off as well, so its not a problem with the brakes being locked on.
Thanks
Rob

[Georgeb]

Check throttle position sensor 
I’ve had problems with that sensor in trucks

[Fulltiming]

Do you hear any air leak at the transmission. https://www.youtube.com/watch?v=vvsp_eNPxvo