HEMTT Lockup Solenoid

[Gman021]

The mechanic who has my truck is having trouble finding a wiring schematic for the lockup solenoid on the Allison 740D.

I had a new transmission installed but in a short test drive he didn't think the solenoid was locking the torque converter. Unsure if the solenoid works, but he thinks it does.


Any information about how this system works and is wired would be greatly appreciated.

 

[Gunzy]

I can't help with the diagram but I do know they have a different operation than most. Mine locks in all gears but also has to unlock before shift. So if you watch the tach for RPM changes it will appear to have 12 shifts. That is in a trans that is up to temp. That Allison doesn't like to shift well when it is cold. I am no trans specialist, your experience/mileage may vary.

 

[Gman021]

I can't help with the diagram but I do know they have a different operation than most. Mine locks in all gears but also has to unlock before shift. So if you watch the tach for RPM changes it will appear to have 12 shifts. That is in a trans that is up to temp. That Allison doesn't like to shift well when it is cold. I am no trans specialist, your experience/mileage may vary.

Thanks for the input. Looks like it isn't doing that on test drives.