Starter/ manual trans wiring
 

Hi all, just swapped a rebuild trans into my 89 gtus. I had labeled the wires running to the starter, but the marking/ labels wore off when I spilled power steering fluid all over the place.
Is the top terminal on the starter solenoid (which is a little tab) a ground connection?

Also, here's a pic of a wire with an odd black box on the end, which I think was connected through the bolts on the slave cylinder. What is this thing/ where does it go?

Those little computer chip looking things are condenser for the electrical system. One for the oil pressure gauge and one for the coils. The starter solenoid has a Black/White wire running to it from the starter cut relay.

This single terminal 0.250" Quick Disconnect type connector is technically from the Ignition switch and supplies 12v+ to the starter solenoid's Switch terminal when the key is in the START position. If the car does NOT have a factory alarm, there is a jumper wire in place of the Starter cut relay. You can verify it with a multimeter.

Thanks for the help,
so is that wire correctly installed in the picture I provided!?

Also, oddly enough, the ground wire running from the top of the trans case to the starter solenoid somehow shrank in length while the trans was out...

The pictures aren't showing up for me, so I'll cover all the bases here:
1. The Starter Solenoid switch wire will only read 12v with the key in the START position. Otherwise, it shows 0v. Grab your multimeter to identify it first.
2. The Condensers can be left unplugged during this test. Once you identify the Starter solenoid switch wire and connect it to the starter, plug the consenders back in. IIRC, they are identical and use the same connectors. For reference, their purpose is to 'smooth' out the oil pressure sender's signal so the needle isn't jumping around like crazy. I would imagine the other one smooths out the ignition system as well.
3. The starter only has 3 wires going to it. Ground, run to one of the starter mounting bolts from battery negative. Power, from battery positive to the starter solenoid stud terminal NOT occupied by the cable from inside. Switch, the 0.250 tab terminal from the ignition switch.

Ahh thanks for clearing that up about the condensor.

I found one smaller quick connect wire that only read 12v with the key in the start position, so I will try that as my starter solenoid switch wire. I found that there is a very large all black wire running to the left side terminal on the solenoid, which has 12v all the time. As for the ground wire, I believe there is a larger black wire with a yellow stripe hanging near the starter, which I will ground through the left starter mounting bolt, and see if that works. Thanks! I'll post back with my results.

If you have an S5 then the wire running to the solenoid is Black/Red and not B/W.

The smaller wire running to the terminal on the very top of the solenoid should be black/red?
I am pretty sure I tested that wire with my multimeter and read 0v with key in the start position and 0v with the key off

The clutch needs to be depressed also w/key to start to create voltage on the B/R wire. And if the car has the factory alarm it would need to be operating properly.

Yes the clutch was depressed when I tested the voltage of the red and black wire

The B/R wire comes from the clutch interlock switch located at the very top of the clutch. The switch has a Black/Green wire besides the B/R wire. A continuity test on the B/R wire at the switch and B/R wire at the starter will determine whether or not it is the proper wire.

Locate the starter cut relay. W/key to start the Black/Blue wire should have voltage (no need to depress the clutch). If the relay and the alarm were working properly then the thicker of the two Black/Green wires would have voltage as well (again, clutch does not need to be depressed). If all this checked out then the B/G wire at the interlock switch would have voltage w/just key to start.

Thanks for the help everyone,
I connected the black/red wire (which is right next to the large black wire which has 12v all the time) to the top of the starter solenoid, and sure enough, it fired up.