Clutch vs Neutral vs both Switches [Archive]

PMD24

01-21-2026, 06:45 PM

Been kicking this around in my head since I'm at that point in my wiring. I've repurposed the rear harness speed sensor wires to tie into the neutral switch but would like to hear opinions on clutch switch vs neutral switch vs both/either (series/parallel). Thanks in advance for offering your thoughts.

Pat

Waterman

01-21-2026, 07:09 PM

I start me car often by learning over, checking tran is in neutral and starting it up. I have the TKX and wired in a relay, since the neutral micro sw can not handle much current. I do not see the sense in ALSO wiring in the clutch since if you are sitting in the car you will normally place tranny in neutral before pushing in clutch. If not in neutral car will not start. I am the one that will drive my car 98% of the time and the other 2% I will be right there as others start it. Neutral safety is the way for me.

OB6

01-21-2026, 07:43 PM

I have the normal clutch switch with a momentary override switch wired in parallel and mounted under the dash so I can start the car without getting in. Works great.

CraigS

01-22-2026, 08:13 AM

On 99% of oem setups the clutch needs to be pushed fully to the floor to start the engine. If one could rig a switch like that on an FFR it would be great. But w/ the switches generally used, all you need is to push the clutch 1-1.5" and it starts. Unfortunately the clutch is still engaged at that point so the switch is worthless. I used the neutral switch on my TKO500. Back in the 70s before clutch switches were universal, I started a car in out shop. Unfortunately it was in first and ran into my workbench and pushed it against the outer wall of our steel building. Effed up the bumper, grill, hood and a headlight on the customer car as well as our building. I can tell you that, as that car leaps ahead, there is no way you will keep up w/ it to get to the switch to turn it off.

OB6

01-22-2026, 09:48 AM

rich grsc

01-22-2026, 10:14 AM

My pedal must be pushed fully before switch will activate the starter. It's adjusted correctly, common sense would tell you that is how it should work. It's up to YOU the builder to put the car together correctly.

skidd

01-24-2026, 06:50 PM

My 02c
I wired them both in parallel.
I can start my car if either the clutch is in, or it's in neutral. It's been handy for those tuning days when I want to start it without getting in to press the clutch. Or.. say.. advance the distributor a few degrees or something. It was worth the few more connections. Basically they each provide a ground path for a standard relay coil circuit, which then feeds power to the start solenoid.

edwardb

01-24-2026, 10:12 PM

There's no right or wrong answer. Like many aspects of these builds it's personal preference. Every build I've completed to date had a clutch safety switch. I'm used to it so no big deal. I would never consider leaving it off. Even though I think I'm as careful as the next guy, it would only take one momentary lapse to cause serious damage or worse. I do share concern that the standard setup doesn't require the clutch to be fully depressed to trip the switch. I guess the thought is if you press it a little you're going to press the pedal all the way down. Far enough to disengage the clutch. It's a moot point for a Coyote build, my last couple builds, since they have a bottom switch as standard.

Having said that, for my Mk5 build I decided to add the neutral safety switch in parallel to the clutch switch. There have been times -- admittedly only very occasionally -- that it would be nice not to have to climb in to start and then get right back out. While doing maintenance, whatever. It's a simple add to include the neutral switch in the circuit. Wired in parallel, either can allow the engine to start. Zero downsides IMO. My build is a Coyote (Aluminator) so the safety switch doesn't carry any appreciable current. The PCM is just looking for continuity to allow the start. So nothing special, e.g. a relay, to use the TKX switch. I added the wires while doing some other mods to the rear harness. I need the speed sensor wires so couldn't use those.

F500guy

01-26-2026, 09:23 AM

I added a relay behind the dash to activate on Neutral transmission position or clutch-(parallel arrangement) and been very happy to not have to climb in when playing with the engine. When I was a teenager, had a 68 mustang that I changed the clutch on, it was a faulty new pressure plate and when I went to test it the motor cranked and the car launched off the ramps, hit the garage wall...I always remembered that to this day so it was planned from the beginning of my build.

GoDadGo

01-26-2026, 07:22 PM

Here is what NOT to do but I did it anyway.

1. I don't have a Neutral Safety Switch.
2. I don't have a Clutch Safety Switch.
3. I have a separate Keyed Barrel Switch that I use as an anti-theft device

I do like having the ability to start the car in gear because my old 1969 Chevy C-10 truck was the same way.

Again, I DON'T recommend doing this.

BornWestUSA

01-26-2026, 08:25 PM

I removed the clutch switch because it had been installed incorrectly by the person who started the build, it was limiting the total clutch pedal travel by over one inch.

I left it out because I'm old school. I was raised on cars/trucks with no neutral switch so that just feels "normal".

Need to start it while standing outside the car? No problem. First verify it's in neutral, left hand on the throttle linkage, reach in and push the start button.

bobl

01-27-2026, 01:56 AM

I'm in Go-dads camp. No neutral safety switch and I wired the clutch switch into one of the inputs to the ecu. I programmed that into a rev limiter, so I use it as a 2 step and secondly a rev limiter with the clutch depressed in case you get the urge to power shift and aren't fast enough. I've also used the starter several times to pull the car into the trailer when the engine wouldn't start, or to just spin the engine over without having to get into the car. At the least I'd add a button that will bypass the safety switches

Bob.

GoDadGo

01-27-2026, 08:45 AM

NOTE:..Don't do what Bobl & I did unless you are over 60 years of age and grew up driving a stick shift or like I did shifting 3 on the tree.

Pete&Scott

01-28-2026, 08:26 PM

My Blueprint 427 Engine and TKX transmission arrive tomorrow. I like the idea of a neutral switch wired in parallel to the clutch switch. No experience with installing a Neutral switch. Would appreciate some details on wiring one up. Will my TKX have a built-in neutral switch that I need to connect a wire to, or will I need to order a switch? Several mentions of a relay. Do I need to buy a relay? If so, what type of relay do I need? Parts numbers or a picture of a relay would be appreciated. To make it parallel to the clutch, is that just a matter of connecting the wire from the transmission to the wire coming from the clutch? Thanks for your help.

PMD24

01-28-2026, 09:01 PM

Yes, your TKX will come with the switch. It will be on the driver's side, a pigtail with a connector on the end. Your Blueprint FAQ doc will have photos of the TKX with the switch pointed out. My understanding is the switch is not rated for the circuit taking current to the starter solenoid and therefore a relay will be needed. The RF harness does not have wiring for the neutral switch so you will need to plan on that. You can either run new wires to that switch or use wires in the harness that may be free. In my case I used the e-speedo wires because I have the Vintage Gauges and they have their own GPS based speed sensor, so the e-speedo wires were unused. I still have to purchase a relay and sort out the wiring to tie mine in. Still undecided if I will keep the clutch switch, but will definitely be doing the neutral switch. I'll post details in my thread. Your first step will be making provisions for the wiring from the switch to the dash. You will have plenty of time later to sort out the tie-in to the start circuit, relay, etc.

Pat

F500guy

01-28-2026, 10:56 PM

This was my layout for the neutral safety switch...I did leave a pig tail for a bypass, but never put it in.
224848

edwardb

01-29-2026, 09:38 AM

This video does an excellent job of showing how a relay can be wiring into the neutral safety switch. It's for a TKO but the TKX is the same. Also references an American Autowire harness. But the principles still apply. Just to emphasize, again, a relay is only necessary if the RF start wire is carrying voltage/current to the starter. For a Coyote build the switch is only used for continuity to signal the PCM. The Coyote control pack start wire has the actual voltage/current.

https://www.youtube.com/watch?v=lJ8B6Iim_F4

Justin

01-29-2026, 10:22 AM

Interesting to see the different opinions. I wired mine so EITHER the trans is in neutral OR the clutch is pushed in. This way there are no accidents. I do have a push button, in reach of the passenger, and I want to be able to start the engine without sitting in the car.

ggunter

01-29-2026, 11:07 AM

Having worked on trucks most of my life I learned a very valuable lesson early on in my career about 50 years ago. I was working on a Detroit Diesel and standing outside the cab and just wanted to bump the starter to position the fan to get to a bolt on the front of the engine. The starter button was just inside the door, so it was easily reachable from outside the cab. I knew it was in neutral......The old Detroit Diesels need about 1/4 turn of the crank to start. Guess what? Off she went into another truck in front of this one and both went into the wall at the end of the shop. Luckily no one was in or around both trucks. Took me quite a while to pay for the damage to both trucks. My lesson learned was always check for neutral before hitting that key. So, having said that, I dislike the clutch switch but do like a neutral safety switch. As a habit most people will automatically grab the shifter and check for neutral as soon as you hit the seat. It's a pain to have to get in and out of the car to crank the engine if you are working outside the car and need to bump it. I switched over to a neutral safety switch and removed the clutch switch because I can work outside the car and it's not going to start unless the neutral slot is engaged. I did that to be able to install a starter button in the engine compartment for various things like finding TDC, dropping in a distributor adjusting valves etc.

rickster991

01-29-2026, 02:23 PM

I have a wiring question. I opted for the neutral safety switch. My BP 347/TKX did not come with the wiring harness, so I bought this:

https://www.summitracing.com/parts/rfw-pg052

I did not use a relay, I simply connected it to the RF harness where the clutch switch would have connected. It has been working great for 1000 miles. Do I need a relay?

rickster991

01-29-2026, 03:27 PM

Looking at the RF harness I think I answered my own question. It is the exact setup the video describes. Looks like I need to add a relay.

skidd

01-29-2026, 04:13 PM

Need? Is always dependent on your particular setup.
In my case, my starter is a push button. One of those S2000 push buttons. They are not really designed to handle the current passing through them to trigger a normal starter relay.
So, in my car, I already needed a relay in just for that. The Push button triggers the Bosh style relay, which in turn then triggers the main starter relay.
Thus, the "ground" side of the coil circuit for the bosh style relay, which is quite low current, travels through the Clutch switch or the Neutral Safety switch , which ever one happens to be closed to ground at the time.
It's my understanding that most (if not all) clutch switches, and neutral switches are heavy enough to handle the load of a typical starter relay. And if you have a normal "Key" starter that also can handle the current, you might not need a relay like I did.

edwardb

01-29-2026, 04:15 PM

Amazing to me how some specific topics get a lot of interest and emotional responses on both sides. This happens to be one of them. I've already stated I'm in the camp of having one or both of the described safety switches. Done properly there's no reason for this to detract from operating the vehicle. In fact most of the time you won't even know it's there and your man card isn't in jeopardy. In my past I had a similar event as ggunter described. Not going to try to explain what happened, other than I had a sudden unintended acceleration (SUA, it's a known acronym) that put a dent in my garage wall and minor damage to the vehicle. I watched it happen like it was in slow motion not really believing it. I was able to fix both but it was sobering to think what might have happened if someone had been in the front of the vehicle. It can happen to anyone. Do the right thing folks. Stepping off soap box.

rich grsc

01-29-2026, 04:46 PM

Man, I was just about to post a similar response. This post just gets drug out & out. Don't want one fine, it's your responsibility. I have one and always will

Mike.Bray

01-29-2026, 05:08 PM

Good points Paul. I think we can recap:

No safety interlock (we die like men). Not recommended, easy to accidentally start the car or truck and have it drive away or into something/someone.

Interlock only on clutch. Most OEM cars use this setup. Need to insure the clutch is fully engaged before the interlock is made.

Interlock only on transmission neutral switch. Switch is low current design so may require a relay.

Interlock on clutch & neutral switch in series. Double safety setup requiring two interlocks to be made. Get rid of your man card.

Interlock on clutch & neutral switch in parallel. Good redundant system that allows you to keep your man card.

Any interlock system with a manual bypass switch. Back to being able to die like a man.

rich grsc

01-29-2026, 05:37 PM

Mike, what do snowflakes get??

PMD24

01-29-2026, 07:13 PM

Thanks to all who weighed in on this topic.

Thank you to Mike for the stellar summary.

Let's close it out with that.

Pat

Pete&Scott

01-30-2026, 10:48 AM

PMD24

02-01-2026, 06:19 AM

Thanks. Everyone, for the help in figuring out the Neutral Safety switch. I learned a lot from all of the conversations.
Best I can figure out, these are the parts needed for wiring up the switch on a TKX transmission
224872

You don't need the pigtail. Since you're connecting a pair of wires with butt connectors, simply cut the connector off the TKX and use the butt connectors there. Solder or crimp with proper crimping pliers and seal with adhesive lined shrink tube.

Also, there is no provision in the RF Harness for the neutral switch, so you'll need to sort out wiring.

Pat

OB6

02-04-2026, 10:23 AM

Ted G

02-04-2026, 11:05 AM

I only run a neutral safety switch and I LOVE it! I don't have to get into the seat each time i start the car and I can tinker with the carb if necessary. I did put my Ford switch (changed from the FF) on the left side of the wheel and its just a nice touch. You will definitely need a relay as the switch isn't meant for full 12v. Getting in and out of these cars is a challenge at times and this is just a nice way to warm them up without getting in/out.

225127

TrackDay17

02-04-2026, 11:12 AM

Just a PSA for a limited number of people this may apply to. Installing a midshift kit on the TKX renders the neutral safety switch inoperable. I recall Mike Forte telling me the same about reverse lockout, but I never asked about the NSS. I confirmed this with my multimeter last night. That said, knowing this wouldn't have prevented me from installing the midshifter.

This I didn't know, I was planning on just wiring up the NSS and not the clutch switch, I guess I may have to switch this up.
I went with the mid shift on my build.

Ted G

02-04-2026, 11:15 AM

This I didn't know, I was planning on just wiring up the NSS and not the clutch switch, I guess I may have to switch this up.
I went with the mid shift on my build.

When you say mid-shift, are you talking about the most forward shifting position of the three? I have mine set up in the middle position and the NSS works fine.

225129

Mike.Bray

02-04-2026, 11:19 AM

I can tinker with the carb if necessary.

Like this? :rolleyes:

225128

Ted G

02-04-2026, 11:21 AM

Like this? :rolleyes:

225128

HA!

TrackDay17

02-04-2026, 11:25 AM

When you say mid-shift, are you talking about the most forward shifting position of the three? I have mine set up in the middle position and the NSS works fine.

225129

I'm not sure if it is the most forward position available on the TKX or not.
I was under the impression there was one more forward position that could be used in other applications but I don't know.
I ordered mine as a mid shift from Blueprint when I ordered my 347 package, I wasn't fond of the dogleg shifter unless I was going to build an old school looking car.

So I hope you are correct Ted and mine will work.

OB6

02-04-2026, 11:51 AM

When you say mid-shift, are you talking about the most forward shifting position of the three? I have mine set up in the middle position and the NSS works fine.

225129

Good clarifying question. I'm talking about this:

https://thefactoryfiveforum.com/attachment.php?attachmentid=195025&d=1706393546

JMD

02-04-2026, 02:15 PM

The forward most position in the above picture is considered the 'mid shift'. That's what I have. I didn't even try to wire up the NSS though. Just the clutch safety for me.

RogerRoger88

02-04-2026, 02:53 PM

Mike, what do snowflakes get??

They don't get to own/drive a Cobra. They only get a Toyota Prius.

TrackDay17

02-04-2026, 03:15 PM

The forward most position in the above picture is considered the 'mid shift'. That's what I have. I didn't even try to wire up the NSS though. Just the clutch safety for me.

JMD, mine is the same, I'm going to wire mine up and I guess I'll see if it does work.

OB6

02-04-2026, 03:30 PM

JMD, mine is the same, I'm going to wire mine up and I guess I'll see if it does work.

If yours is the same as the photo I posted of my TKX above, then I'm not sure I'd bother wiring in the NSS. Mine is a Fortes kit (installed by them), but it's the same situation for all others as well. In fact I stumbled on a reference to this in the instructions for Silver Sport Transmission's TKX midshift kit when I researched a little further. Evidently the internal mechanism that operates the stock neutral safety switch is bypassed.

rickshank

02-04-2026, 03:41 PM

If yours is the same as the photo I posted of my TKX above, then I'm not sure I'd bother wiring in the NSS. Mine is a Fortes kit (installed by them), but it's the same situation for all others as well. In fact I stumbled on a reference to this in the instructions for Silver Sport Transmission's TKX midshift kit when I researched a little further. Evidently the internal mechanism that operates the stock neutral safety switch is bypassed.

Correct. And it's a "front shift" kit, the mid shift is (I think) considered the rotated shifter. Just dropped my 347/TKX in my MKV with the front shift kit installed.

OB6

02-04-2026, 03:50 PM

Correct. And it's a "front shift" kit, the mid shift is (I think) considered the rotated shifter. Just dropped my 347/TKX in my MKV with the front shift kit installed.

It's definitely located in the front of the transmission, so I'm not sure why the kits are all refered to as "midshift".

Pete&Scott

02-06-2026, 01:15 PM

Looks like I didn't need the pigtail or the relay per a Perplexity AI response.

Leave the relay on the shelf and wire like this:

Keep the existing clutch switch exactly as it is between the two RF light‑blue wires. Splice the TKX light‑blue wire into one RF light‑blue at the clutch switch (call it RF‑LB1). Splice the TKX black wire into the other RF light‑blue at the clutch switch (RF‑LB2). That gives you two parallel paths: RF‑LB1 → clutch switch → RF‑LB2, and RF‑LB1 → TKX switch → RF‑LB2, so either clutch depressed or trans in neutral closes the RF safety loop.

You’d use the 40 A relay only if:
You were running full starter‑solenoid current through the safety switches (older generic harnesses sometimes do this), or Tremec explicitly rated your particular neutral switch as a low‑current ECU‑input only and you wanted extra insurance. On the Factory Five/Ron Francis Roadster harness, that light‑blue safety loop is a low‑current control circuit to the starter output (purple), so your TKX switch, paralleled at the two light‑blue wires, is fine without the relay.

You don't need the pigtail. Since you're connecting a pair of wires with butt connectors, simply cut the connector off the TKX and use the butt connectors there. Solder or crimp with proper crimping pliers and seal with adhesive lined shrink tube.

Also, there is no provision in the RF Harness for the neutral switch, so you'll need to sort out wiring.

Pat

PMD24

02-07-2026, 09:07 PM

I'll have to do a little more research on the TKX neutral switch amp rating. I didn't make a note anywhere on where I found it, but I did find an amp rating and it was less than the draw from the starter solenoid. It might be worth creating a separate thread on wiring the TKX neutral switch so we get input from the experts on whether that switch can handle the load on a regular basis. I'll update this post if I find anything in my searching.

Pat

Nigel Allen

02-07-2026, 09:16 PM

The inrush current on the starter solenoid is heaps. Recommend a relay for reliability.

PMD24

02-08-2026, 09:11 AM

Looks like Nigel is correct and Perplexity is... perplexed:). Tremec video specifically stating that a relay is required. If you want the clutch switch as well, simply connect it across the two leads from the neutral switch and it will then be in parallel, and either will trigger the relay.

https://www.youtube.com/watch?v=lJ8B6Iim_F4

Pete&Scott

02-11-2026, 10:07 PM

Interesting. I have a TKX I wonder if that is different from the TKO in the video. The video of the TKO appears to operate differently from the TKX in that the TXK is just a switch with an in and out circuit. The TKO states that one line goes to ground, and the other line runs to the relay and then to the starter/solenoid. I don't think the TKX switch and the clutch safety switch wires run to the starter/solenoid. In regard to Nigel's comment about inrush, since these switches do not connect directly to the starter/solenoid, I don't think they see inrush from the starter/solenoid. I have connected the Neutral switch in parallel with the clutch switch. To my knowledge, the FFR RF harness does not include a relay for the clutch safety switch. Good discussion, I am trying to learn, all this wiring stuff is very confusing, and the FFR RF manual could use some massive upgrades.

Looks like Nigel is correct and Perplexity is... perplexed:). Tremec video specifically stating that a relay is required. If you want the clutch switch as well, simply connect it across the two leads from the neutral switch and it will then be in parallel, and either will trigger the relay.

https://www.youtube.com/watch?v=lJ8B6Iim_F4

edwardb

02-11-2026, 10:56 PM

This thread just keeps going and going... Just want to emphasize again that for the 50% or so that are doing Coyote builds (that's the number Dave Smith often cites) and using the Ford Performance control pack, you can use the TKX neutral switch without a relay. The clutch safety switch in the Coyote harness replaces the RF clutch safety switch and does not carry current to the starter solenoid. It's only a continuity signal to the Coyote PCM to allow the start. The TKX neutral switch, if used, would also only provide continuity and wouldn't carry any current requiring a relay. The Coyote control pack has its own start wire to the starter solenoid.

PMD24

02-12-2026, 09:00 AM

Interesting. I have a TKX I wonder if that is different from the TKO in the video. The video of the TKO appears to operate differently from the TKX in that the TXK is just a switch with an in and out circuit. The TKO states that one line goes to ground, and the other line runs to the relay and then to the starter/solenoid. I don't think the TKX switch and the clutch safety switch wires run to the starter/solenoid. In regard to Nigel's comment about inrush, since these switches do not connect directly to the starter/solenoid, I don't think they see inrush from the starter/solenoid. I have connected the Neutral switch in parallel with the clutch switch. To my knowledge, the FFR RF harness does not include a relay for the clutch safety switch. Good discussion, I am trying to learn, all this wiring stuff is very confusing, and the FFR RF manual could use some massive upgrades.

I encourage you to review the RF wiring schematic. Follow the blue wire from the ignition switch through the clutch switch to the solenoid. That wire and the clutch switch see full solenoid current draw, including inrush, and there is no relay involved.

I spoke with Tremec a few minutes ago and tech support confirmed that the neutral switch is not designed to carry the solenoid current and should be wired through a relay.

Pat