Personally if I had a choice between a neutral switch in the trans or a switch on the clutch pedal I'd choose the later.  Its good to have one or the other though so you can't accidentally start the car in gear without the clutch in. 

I would guess that they include that switch because the TKX is now Tremec's go to 5 speed swap trans, which means guys are likely going to put them in some applications which has a neutral switch from the factory (like Fox Mustangs). 

As to where the wire goes, that depends on the way the harness is configured.  If I were to design it from scratch I would use the switch to switch ground, not power.  That's how most of the switching in modern cars works.  It also doesn't require as much heavy gauge wire.  If I had a diagram for the Painless harness I could tell you exactly how to wire it, but without that I'm limited to just being able to give you general advice.  The wire for the NSS is probably intended for use in cars with either an automatic or a stick, and if its a stick it probably becomes a clutch pedal switch.  When I converted my '86 IROC from auto to manual I looked at the diagrams for both and that was the difference from the factory, so I rerouted that wire through the clutch switch.  It was a heavy gauge yellow wire as I recall (probably hot all the time based on the color), and it may have gone directly to power the ignition switch after the switch, but I'm going back 20+ years now and am not 100% certain of that. 
 

Yes, given the option that's how I would wire it.  The switch just grounds the relay enabling the ignition switch to power the solenoid and spin the starter. 

Just be mindful it will start without the clutch pushed in provided its in neutral.  If the trans get banged into gear accidentally, etc. it could move.  I'm probably overly paranoid about that stuff because my youngest almost started my tractor when he was 3.  I never used to take the key out of it prior to that. 
 

I edited your picture Mark to clarify the wiring as TKO mentioned.

The “neutral” switch on the T5 was used only for the ECM for neutral indication.
I have read of many failures due to running full start solenoid current through this switch.

The actual “neutral safety switch” on the Foxbody Mustang was actually 2 switches under the dash…one for ECM (parallel to the transmission neutral indicator switch) and one for start circuit (start solenoid).

Just wanted to prevent someone else reading this from getting corn fused.
Sounds like a nice upgrade.

Nos681 wrote:

I edited your picture Mark to clarify the wiring as TKO mentioned.

The “neutral” switch on the T5 was used only for the ECM for neutral indication.
I have read of many failures due to running full start solenoid current through this switch.

The actual “neutral safety switch” on the Foxbody Mustang was actually 2 switches under the dash…one for ECM (parallel to the transmission neutral indicator switch) and one for start circuit (start solenoid).

Just wanted to prevent someone else reading this from getting corn fused.
Sounds like a nice upgrade.

Whats the box where the 4 wires are connected too?

Can’t figure out how to respond to individual posts but thanks for all the advice.

NOS681- good catch on the wires from the NSS. The switch does have separate  power and ground and when you watch the actual video from Modern Driveline  it does address both connections. 

Now, if one wanted to add a safety switch to the clutch pedal on a vintage mustang, is there a switch that can be retrofitted to the pedal somehow? And how would it wire? Would the power go from the ignition switch to the clutch switch to the starter solenoid bypassing the NSS on the trans?

My car is a 65 Fastback with standard clutch pedal assembly. I have a Blueprint 302 crate engine package with TKX trans sitting in the corner of the garage. I’m trying to find a body shop in the Phoenix area to finish body and paint before dropping the engine in. In the meantime I’m working on getting the Painless harness finished up. So, to answer your question, it is not set up for a neutral safety or clutch safety switch.

True story: About a year ago I was on a first date and we took the Mustang up the coast. I put the battery on a battery charger until the charger showed full charge. Stopped for fuel and the battery had just enough juice to turn the engine over, but not enough for a hot start. Asked the date "Can you drive a stick" "It's been a long time." 

Tell the date she is pushing and push she does, but she only had enough "Oomph" for a slow roll. I let the clutch out and hit the starter at the same time, and to my relief, the car started. Car would not have started with just the date's efforts. Drove home and determined the battery was dead. Still with the date.

I have used this technique several times over the years, especially when I am the only one pushing. My two cents: Unless you really have to have it, you might consider bypassing any starter interlock device on these cars and develop a habit of finding neutral before you start the car.
 

Last edited by boss347convertible (12/06/2023 7:45 PM)

I’m 67 years old. Never had a car with neutral safety and really don’t NEED it now. Looks like I’m going to by-pass the switch…thanks for all of your suggestions.

Mark in CA wrote:

I’m 67 years old. Never had a car with neutral safety and really don’t NEED it now. Looks like I’m going to by-pass the switch….

Good on ya Mark of Ga/Ca...
I was just "fix'in" (that's southern-tawk y'all)  to light everybody up!!
Out of my 60 years behind the wheel I have most always cranked the engine when out-of-gear or with the clutch depressed. THAT is part of driving a standard shift/manual trans. DUH
WHY open your self up for more issues of failure or stuff-that-happens by installing an electrical
"SAFETY" switch in case someone goes STUPID and cranks an engine while in gear and is
SOOO klutzy they continue to crank it over until they hit something or run over six pedestrian and kill them ALL ! Don't we already have TOOO much government 'do-gooder crude' in our lives now ?!
For gosh sake guys..... man-up & pay attention and enjoy a vehicle that was made for people smart enough to operate them !
SAFETY SWITCH MY FANNY !!! GOOD GRIEF
6sal6

Mark in CA wrote:

Can’t figure out how to respond to individual posts but thanks for all the advice.

NOS681- good catch on the wires from the NSS. The switch does have separate  power and ground and when you watch the actual video from Modern Driveline  it does address both connections. 

Now, if one wanted to add a safety switch to the clutch pedal on a vintage mustang, is there a switch that can be retrofitted to the pedal somehow? And how would it wire? Would the power go from the ignition switch to the clutch switch to the starter solenoid bypassing the NSS on the trans?

To respond to a particular post just click the blue "quote" icon at the bottom right of that post.  The post to which you are responding will appear first in quotes, and then you can reply.  It does help reduce confusion.

A lot of good points were made.  If you don't want to use the NSS just ground the relay and don't connect anything to the switch.  It won't do anything except plug the hole its in.  Then run the NSS wire to wherever it was supposed to go after the NSS. 

I still like having a clutch pedal switch, but I do see the point about a roll start.  My FJ Cruiser has a bypass switch for the clutch pedal switch to allow this.  It adds even more complexity though, but just thought I'd put it out there as an option. 

Yea the slow roll key start saved my but a few times.

Been driving stick all my life. There were times when I didn't have a vehicle with an auto in my driveway. Up to about ten or twelve years ago, I always had at least 1 of my main vehicles with a stick. (Last was a 04 Fusion) Agree with Sal, just habit pushing in the clutch before starting. There were times when I was in a automatic I'd catch myself reaching for a clutch.

I'll add my 2-cents:
The neutral switch will not allow the car to start unless the trans is in neutral. (doesn't matter if the clutch pedal is depressed, or not)
The clutch switch will not allow the car the start unless the clutch pedal is depressed. (doesn't matter if the trans is in neutral or not).
IMO - Having both a clutch switch and a neutral switch wiring in is like wearing 'belts and suspenders".
I'm not sure a relay is needed, I suggest asking Tremec.
If you're not going to utilize the neutral switch, you'll need to verify the the 'start' wire from the ignition switch is continuous to the start solenoid.  The neutral switch would go in 'series' with the start wire.  The neutral switch has a closed contact only when the trans is in neutral.  If not used, you'll likely have to connect the two wires for the neutral switch.