The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - does anyone have a 3speed with overdrive?

**pjmoreland** · 05-03-2005, 11:59 PM

I had a manual 3 speed with an overdrive on my 67 swb. It had a silver t-handle knob marked "OVERDRIVE" attached to the bottom of the dash. The t-handle was connected to a cable that actuated an arm on the overdrive unit. When the t-handle was pushed in, it would put the transmission into a freewheeling mode, kind of like a bicycle, where the engine could idle while coasting down the road at highway speed. There was also an electric switch that operated a solenoid in the overdrive unit. In order to shift into overdrive, you had to first push in the t-handle cable, and then rev the engine up, let off the gas, and as the engine rpm started to fall, actuate the solenoid. Once the engine rpm fell down to the correct level, the solenoid would engage the overdrive gear with a little clunk. If you turned the solenoid on too early, the fuse would blow before overdrive engaged. If you turned the solenoid on too late, then the correct rpm would be missed, and the fuse would burn out. If you forgot to shift out of overdrive, and came to a stop, all the gears would be geared up, and it would be difficult to get started in first gear. It was kind of a pain, but I could get 21 MPG on the highway.

05-03-2005, 11:59 PM	#7
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 5,360	I had a manual 3 speed with an overdrive on my 67 swb. It had a silver t-handle knob marked "OVERDRIVE" attached to the bottom of the dash. The t-handle was connected to a cable that actuated an arm on the overdrive unit. When the t-handle was pushed in, it would put the transmission into a freewheeling mode, kind of like a bicycle, where the engine could idle while coasting down the road at highway speed. There was also an electric switch that operated a solenoid in the overdrive unit. In order to shift into overdrive, you had to first push in the t-handle cable, and then rev the engine up, let off the gas, and as the engine rpm started to fall, actuate the solenoid. Once the engine rpm fell down to the correct level, the solenoid would engage the overdrive gear with a little clunk. If you turned the solenoid on too early, the fuse would blow before overdrive engaged. If you turned the solenoid on too late, then the correct rpm would be missed, and the fuse would burn out. If you forgot to shift out of overdrive, and came to a stop, all the gears would be geared up, and it would be difficult to get started in first gear. It was kind of a pain, but I could get 21 MPG on the highway.