Controlling overdrive in an A-518 without an ECU

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Controlling overdrive in an A-518 without an ECU

Postby Bookshelf » Sun Oct 23, 2016 10:11 pm

What would be the best way to control overdrive in a 518 without an ECU, and not using a toggle switch either? Thinking of using one in a repower. With the potentiometer in place of a TPS, I would still need an ECU, right? Thanks
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Re: Controlling overdrive in an A-518 without an ECU

Postby Philip » Mon Oct 24, 2016 6:47 am

TPS means nothing without a PCM in the system. The TPS sends a variable voltage signal that only the PCM can use. The OD solenoid is wanting an on/off ground signal.

Hook a pressure gage into the governor test port. Find the pressure that it supplies for the speed you want OD to come in at. Then pickup a 1/8 NPT pressure switch for that PSI at a parts store. It will turn on/off the OD at the same speed every time.

Now going this way remember if your towing heavy you have no way to delay OD engagement. I would still put some type of over ride switch on OD. Maybe a switch on the throttle linkage that drops the power to the OD above 3/4 throttle
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Re: Controlling overdrive in an A-518 without an ECU

Postby stuffy » Mon Oct 24, 2016 7:17 am

You can also get adjustable pressure switches. I think they're called Hobbs switches
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