Auto to manual conversion problem #4
Thread Starter
Melting Slicks
Joined: Dec 2009
Posts: 3,233
Likes: 657
From: Thunder Bay
Auto to manual conversion problem #4
Working on the wiring for my trans swap tonight. My Tremec TKO 600 has a built in neutral safety switch and I'd like to use it. The problem is the starter circuit in the car uses a 12 gauge wire. The Neutral safety switch on the transmission has about a 16 gauge wire. that tells me the starter circuit could overload the neutral safety wiring on the transmission. I'm thinking I could wire in a relay if I can find one that can handle the current. I would be interested in hearing how others handled this.
Racer
Joined: Dec 2008
Posts: 297
Likes: 19
From: arlington TX
Hi,
Usually, manual transmission cars had a switch on the clutch pedal, so that it would only start if the clutch was pushed in, no matter what gear it was in. If you needed to restart in a hurry (like in the middle of an intersection with a big truck coming at you), just pushing in the clutch would let you do it, instead of having to find neutral also.
In any case, the wire you need would be one of the smaller wires on the starter solenoid (the "S" terminal, I believe).
Good luck.
walt
Usually, manual transmission cars had a switch on the clutch pedal, so that it would only start if the clutch was pushed in, no matter what gear it was in. If you needed to restart in a hurry (like in the middle of an intersection with a big truck coming at you), just pushing in the clutch would let you do it, instead of having to find neutral also.
In any case, the wire you need would be one of the smaller wires on the starter solenoid (the "S" terminal, I believe).
Good luck.
walt
Safety Car
Joined: Nov 2008
Posts: 3,717
Likes: 551
From: Seattle Washington
The easy way is to just find the wire from the Auto Shifter that would only allow the engine to start when in Park. Then run it to the Switch on the TKO 600. That's the way I did it, however I wish that I didn't. There is a reason why GM put the safety switch on the Clutch, because it works better. Once the Clutch Peddle assembly is installed its pretty much impossible to install the switch and all its linkage. I consider this the biggest mistake I made.
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
I went with the neutral safety switch idea and you *must* run a relay. That switch is there for Ford applications to tell the computer that the trans just went to neutral (closes a circuit). It is NOT designed to carry the full current of the starter and will quickly give out if used in such a way.
86: ground
85: 1 side of neutral switch
30: other side of neutral switch, NSS wire from ignition switch
87: NSS wire to starter
When the switch is closed, there will be 12V on 85 and ground on 86 and allow current to flow across the original thicker gauge wire to the starter.
FWIW, I think the clutch safety setup is better overall especially if you drive the car a lot or stall. I pretty much always start cars in neutral as a safety precaution, so it was near a no-op for me. Frankly, though, I did mine the way I did because I was lazy and didn't want to mount the switch or run new wiring to that area.
86: ground
85: 1 side of neutral switch
30: other side of neutral switch, NSS wire from ignition switch
87: NSS wire to starter
When the switch is closed, there will be 12V on 85 and ground on 86 and allow current to flow across the original thicker gauge wire to the starter.
FWIW, I think the clutch safety setup is better overall especially if you drive the car a lot or stall. I pretty much always start cars in neutral as a safety precaution, so it was near a no-op for me. Frankly, though, I did mine the way I did because I was lazy and didn't want to mount the switch or run new wiring to that area.
Last edited by Shark Racer; Jan 9, 2014 at 03:51 AM.
Thread Starter
Melting Slicks
Joined: Dec 2009
Posts: 3,233
Likes: 657
From: Thunder Bay
I probably should have explained things better. My intention is to use both the clutch safety switch and the transmission neutral safety switch. They will be wired in parallel so the engine will start with EITHER the clutch depressed, OR the transmission in neutral. Among the other advantages, that permits me to get the car started if either switch should fail. Wiring a relay is not a problem. My concern is about the current draw in the circuit. The General used 12 gauge wire on the circuit to the starter solenoid. That says to me they anticipated considerable current. As Shark Racer indicated, the neutral safety circuit on the TKO is not designed for that much current. My question at this point is will a conventional automotive relay (the one I have in mind is a Borg Warner RB177) handle the required current? They are supplied with a 14 gauge wire which is still lighter than the 12 gauge the General used. I don't want to fry anything. Anyone have a suggestion for a suitable relay?
Race Director
Joined: Apr 2009
Posts: 19,294
Likes: 2,754
From: Charlotte NC
If you are wanting the neutral safety switch in transmission to work...and it is what will activate a relay...and you want a relay that works for enabling the starter...you will need to get a starter enable relay for a C4 (84-89)Corvette. They are stout...and you can get the wiring connector and relay from many places that part them out. I get them quite often and will work because that is what GM used.
Please excuse me because I am having a severe "brain fart" because GM used two types of relays....one was a "starter enable relay" the other I believe is a starter dis-able relay.
Also On a 1990 Corvette...and I would have to look when I get to work tomorrow..is that I believe there is a relay under the steering column that is also for the starter...that has serious gauge wires going to it.
DUB
Please excuse me because I am having a severe "brain fart" because GM used two types of relays....one was a "starter enable relay" the other I believe is a starter dis-able relay.
Also On a 1990 Corvette...and I would have to look when I get to work tomorrow..is that I believe there is a relay under the steering column that is also for the starter...that has serious gauge wires going to it.
DUB
