Overdrive Safety

1747: Overdrive Safety

overdrive wiring

With the new overdrive safety switch installed and working, it was time to turn my attention to how this car was wired. I learned a lot about Laycock DeNormanville overdrives when I debugged my unit in the 330 America, and there are quite a few places for the overdrive to stop working. One problem I spotted immediately with 1747 was the safety switch was not wired in with the overdrive circuit. Laycock DeNormanville Overdrives can only operate when the transmission is placed in foward gears. If the overdrive is engaged, and the transmission is placed in reverse, the overdrive will be ruined. Ferrari had a safety switch installed expressly to keep voltage from completing the overdrive circuit unless the car was in top gear. Sometime in this car’s past, the safety switch stopped working and the overdrive was not engaging at all, so someone bypassed the safety switch.
mystery wire

It didn’t take me long to find a mystery wire running along the back of the firewall headed for the dash.

An incongruous white knob hinted at something amiss, and sure enough, it was at the end of the mysterious wire. This switch was acting like a manual safety switch, taking the place of the one that failed in the transmission, but the operator would have to remember to pull this switch, along with the one on the steering column to make the overdrive work. Knowing from personal expereince how often I leave the overdrive engaged when coming down from highway speeds,  I felt it it’s too risky to leave this manual switch in place. Since we repaired the switch on the transmission, I removed the extra switch and associated wiring. If the owner leaves the overdrive engaged in fourth gear, moving the shifter to any gear other than fourth will disconnect the overdrive, as it was meant to, and there will be no risk of breaking a nearly irreplaceble overdrive.
overdrive goop

While I was hunting down the wiring, I drained the rest of the fluid to the overdrive. The previous owner admitted not remembering the last time he changed the gear oil in the transmission, so it was probably long overdue. Some of the sludge at the bottom of the overdrive drain was pretty dark!

The screen behind the plug showed no signs of metal particles, so that was a good thing, so things were cleaned up and put back in place.
plug installed

The huge plug was installed, and safety wired in place. Once I get the synthetic gear oil in, I’ll top her off, and she’ll be good to go!
Moved her up a slot

David’s PF coupe had occupied a corner of the shop convalessing over the winter, but we’ve moved her out in direct line of the door because she’s doing so well in her recovery. Just like a rehabilitation facility, 1747 will be soon be excersizing her legs on the grounds, getting some fresh air in the early spring. Her owners will be visiting and spending some time with her, and before we know it, she’ll be heading to her new home, all recovered and ready for new adventures! (Can you tell I’m losing my mind?)

MARK THE DATE: Saturday, May 2nd 2009
The Tomyang.net/ Radcliffe Motorcars Spring Event
12340 Owings Mills Boulevard
Reisterstown, Maryland 21136
Read about last year’s event.
Information on this year’s event.

Just a reminder, I’m looking for a new Vintage Ferrari Project. If you have, or know of a restoration project, please let me know. It would be great to restore another car on this website! My E-mail.

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