1984 4+3 Doug Nash O/D
 

Hi Guys, my gearbox drops into O/D when I take off in first gear, irrespective as to where the O/D switch is, not many guru's down under in Australia that can help me, so I am appealing to owners everywhere,
Cheers,
Mick (Corvette Cutto)

There has to be something else going on. Overdrive is only in 2nd-4th gears.

I would replace the Overdrive Relay on the firewall next to the wiper motor first. The Fuel Pump Relay is identical to it and is located right next to the Overdrive Relay. It's the cheapest and easiest place to start. Not sure myself if it will correct the problem, but for only a few dollars, it's worth the effort.

The wiring above the exhaust manifold on the passenger side, Fuel pump & OD, tend to get too hot and this causes problems. You'll prob need to check here first and get your Volt Meter out and test the relay signals, you'll need an assistant. There where trouble shooting doc's, you'll have much better success !! I loaned my service manual out, never to be returned.....

The insulation (wiring) on my C4 melted off in various spots at and a few out to six inches or so. The connectors that plugged into both relays were discolored and eventually failed. I did replace the harness (to the relays) and new relays,,, Plus an aluminum heat shield that I formed over a Argon tank. Was serious PITA project !! Nasty Gooey sticky black electrical tape.....

The Doug Nash with the OD has several Switches mounted on the Side Cover, 1st, 2nd & 4th, plus the Reverse for the backup lamps,,,if I remember correctly.

My speedo connection leaked early on, which I replace, but thickly coated all the wiring - was a disaster. Brake Clean !! The issue I had at the trans was oil contamination, loose connections, and one switch was intermittent - don't recall which one.

Later one of the small 22 gauge wires to the OD Switch on the shift broke in half. The repair was easy, but only after disassembling the counsel.

You can hopefully find an electrical diagram on-line. Check the Ist gear lockout circuit.

If you can't find a diagram or figure it out, let me know.

Michael...