[Tf175]

The shut down solenoid is electric over air , on top of the governor housing . If I remember correctly there is a lock out that prevents shut down unless  transmission is in neutral . Not certain about this .
Do your gear position panel lights work ? 
Presumably you have checked the Jake wiring . There is a " buffer " switch,  accessed on driver's side that triggers off the idle . I had issue with adjustment of that switch , too much gap . Wasn't activating the Jake . 
You have been putting in time , for sure.  Hopefully you can log miles now !
Chris

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Extra wires in the rear electrical panel are just that . I have found the other end of the extras in the front under the dash , passenger side . These wires can come in handy . Check before using , I have found a couple with DC voltage from mysterious source ...