Welcome to GTT
Please explain what you're referring to when you state "rev counter"? After more thought I think you're referring to the speed/hour meter AKA tachometer. If this is correct the sensor is located on the LH front of engine. Check the wiring & electrical continuity.

 

Yes I mean the speed/hour meter, the wire is missing due to the deer chewing it, which is the correct wire that comes out of the dash

 

 

 

One would probably need to view a 3140 tech manual for wire color code.

 

 

Is that the green plug where the wire goes?

 

Can't help you on that model of tractor, but I'm more curious about how the deer chewed through the wire.

 

They just chewed it when it was sitting in the paddock. Curious beings haha