I'm putting together a 1970 GS steering column, manual transmission, installing a reverse light switch, and see that the Factory Assembly manual calls out a different part number for manual verses automatic cars (3943657 for the manual transmission, 1993456 for the automatic). It sure looks like I can us the automatic switch, 1993456, which I and most of us have (since it's an automatic part)? The manual transmission backup-light plug in the dash harness (green and pink w/black tracer) plugs right into the backup light prongs on the automatic switch. The manual back-drive rotates the column collar when shifting in and out of reverse. I suspect a difference could be if the manual back drive rotates the column collar a different amount than the automatic?
Mike, If you want your backup lights to light in reverse you need to use 3943657 switch. Photo of switch and mounted to column.
On a manual, "park" becomes reverse and turns on the back up lights. I bet Todd has the switch in stock
Thank you "4 speed 4 ever" and Jason. I have found the switch here: https://www.ebay.com/p/Back-up-Reve...its-69-73/15014003038?iid=370369324895&chn=ps Jason, I'm not sure who Todd is? I'd much prefer to support our Buick community! -mike
Here's a comparison of the two switches. Both these switches are substantial and can be easily rebuilt, as I just did with the manual switch that I found this morning and had been sitting decades in the salvage yard.