Neutral Safety switch on 4speed?

[Randy Stockberger]

I'm 'de-bubba'ing the interior of my 1970 4speed 300hp coupe. Bubba disconnected the CLUTCH safety switch and stole the power to run some long-gone electronics. While tracing down the wiring I found the connector at the console for the NEUTRAL safety is unused. The wiring diagram in the AIM has confused me, my question is - what years (if any) did they use a NEUTRAL safety switch on manual transmission corvettes? Do I leave this connecter unused and without a jumper under my console?

Thanks in advance

Randy Stockberger - #32888

[Joe L.]

Re: Neutral Safety switch on 4speed?

Randy-----

As far as manual transmission Corvettes go, a "clutch operated neutral safety starting switch" was used beginning in 1969 and through the end of 1981 PRODUCTION. This wasn't really a "neutral" safety starting switch, at all, so the term is a misnomer. The device was a clutch activated switch which prevented the starter from operating unless the clutch was depressed. The transmission could be in any gear and, most of the time, it was actually in reverse because that's where it had to be when the car was turned off and secured. The theft-preventive transmission interlock ensured this. In any event, if "neutral" is defined as the absence of power to the transmission, then I guess this switch could be called "neutral" start safety switch. The switch, itself, was mounted high up under dash on the extreme left side of the cowl. It connected to the clutch pedal arm via a 1/8" diameter connecting rod specially configured for joining the 2 parts. This switch was GM #1993495.

Automatic transmission Corvettes were another story. They did use a true "neutral start" safety switch which required the automatic transmission to be in the neutral position (or, perhaps, "neutral" or "park" position) before the starter would engage. For 68-81 models with THM the switch was mounted on the automatic transmission selector lever assembly on the console. Three different switches were used between 1968 and 1982.

1958-67 Corvettes with Powerglide transmissions also used neutral start safety switches. These switches were mounted on the left forward outside of the transmission case and connected by thin rod to the transmission gear actuator lever.

[Randy Stockberger]

Re: Neutral Safety switch on 4speed?

Joe:

Thanks for the response. My AIM and the Haynes book both have nearly identical wiring diagrams. They show both switches, the under dash switch is labeled 'Clutch Safety Sw' and the transmission switch is called a 'Neu. Sft. Sw.' Apparently the wiring harness, at least in 1970, services both the 4speed and auto with the unused connector left unused and unjumpered.

Randy Stockberger - #32888

[John H.]

Re: Neutral Safety switch on 4speed?

Randy -

That's correct - there's a splice in the harness such that power from the "start" terminal on the ignition switch to the starter solenoid (the 12-ga. purple wire) is fed two ways - to the clutch safety switch connector and to the automatic neutral safety switch connector, and proceeds to the starter solenoid through whichever of the two switches is installed. In your case, it goes through the clutch safety switch and the connector provided in the console for the neutral safety switch just sits there, un-jumpered.

[Jack H.]

FYI

This feature of the Shark cars IS verified during both Operation Check and in Performance Verification at NCRS meets.... Not needed in a daily driver application, but why not re-connect & make active--it could save an accidental engine start some day/somewhere?

[Randy Stockberger]

Re: FYI

Jack:

I have reconnected the clutch safety switch. I doubt I will ever show the car, it has been touched by too many hands to garner any real points so that is not a consideration to me. I do agree 100% about the safety issue.

Because of this thread I've come to realize that I am also missing the mechanical interlock between the ignition lock and transmission reverse gear. That will go on the todo list since it is not a safety issue.

Thanks

Randy Stockberger - #32888