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Is it possible to drill out and tap the back up light boss on a FC trans?
Posted by: ral1963 ()
Date: June 28, 2020 04:36PM

So as part of my 3.08 diff project, I picked up a 64 FC 4 speed transmission with the 3.65 1st gear.

This trans has the boss for the backup light switch, but it is undrilled. Is it possible to drill and tap this boss and use the stock backup light switch?

My original plan was to design and switch near the shifter that engaged the backup light circuit when the shift lever was in R, but was curious about if anyone ever attempted to make the stock backup light switch work in a trans not designed for it.

Rick Loving
Corvair historian & chronicler of useless facts
CORSA
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Chicagoland Corvair Enthusiasts

RAL1963@COMCAST.NET
Just south of Chicago IL

Current Ride
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60 700 Sedan 80hp PG
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Re: Is it possible to drill out and tap the back up light boss on a FC trans?
Posted by: vairmech ()
Date: June 28, 2020 04:49PM

It's a 1/2-13 thread and I think if you use a bottoming tap you should be able to get the threads deep enough.

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

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Re: Is it possible to drill out and tap the back up light boss on a FC trans?
Posted by: Timothy Shortle ()
Date: June 28, 2020 07:59PM

I am sure it is possible although I have never done it Rick. But I also believe your FC 4 speed case is more rare than a car case. Also the car back up light switch location leaves a lot to be desired. So you know where I am going with this.
Just my opinion of course which you have not asked for.

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Re: Is it possible to drill out and tap the back up light boss on a FC trans?
Posted by: RexJohnson ()
Date: June 28, 2020 08:05PM

I have 2 or 3 of those transmissions and I think that the hole is drilled with a welch plug covering it up. You might try tapping on it and see if it comes loose.

RJ tools
Salem,Oregon

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Re: Is it possible to drill out and tap the back up light boss on a FC trans?
Posted by: Ed Dowds ()
Date: July 02, 2020 01:36PM

I think you would be better off using a switch on the shift linkage as was stock on some of the early Corvairs.

Ed
Hamilton, NJ
66 500 rear 4.3 V6 Corvair
69 350/350 TH Camaro was RS
30 Model A Ford Streetrod 350/400 TH
88 Celebrity Wagon (Daily Driver)

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Re: Is it possible to drill out and tap the back up light boss on a FC trans?
Posted by: joelsplace ()
Date: July 02, 2020 02:44PM

3 speed EM and I'm guessing '65 used it. Clark's used to have NOS switch kits. Might still have some.

Joel
Northlake, TX
5 Ultravans, 114 Corvairs and counting...

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Re: Is it possible to drill out and tap the back up light boss on a FC trans?
Posted by: Frank DuVal ()
Date: July 03, 2020 07:03AM

The trick with using the three speed switch in a 4 speed application is to adjust so the back up lamps do not come on in First and Third Gears!winking smiley

Frank DuVal

Fredericksburg, VA

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Re: Is it possible to drill out and tap the back up light boss on a FC trans?
Posted by: joelsplace ()
Date: July 03, 2020 07:06AM

I'll bet that is right. They are hard enough to adjust correctly on a 3 speed but they are in a protected location unlike that crazy 4 speed switch. I'll bet the car in the GM ad running up the creek bed wasn't a 4 speed. Come to think of it that was a '60 want it?

Joel
Northlake, TX
5 Ultravans, 114 Corvairs and counting...




Edited 1 time(s). Last edit at 07/03/2020 07:09AM by joelsplace.

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Re: Is it possible to drill out and tap the back up light boss on a FC trans?
Posted by: junkman ()
Date: July 03, 2020 07:11AM

You could, but the real question is should you? I wouldn't do it, because the switch is always subject to damage. I would use a 3 speed switch, and they are not that difficult to find. I might even have one in one of the back up kits. A lot easier, with less risk, means a better solution.

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