This age of fluctuating gas prices has classic Pontiac owners searching for a way to drive their cars and not break the bank. Dennis Shearon loves cruising the boulevard in his drop-top '68 GTO, so cutting back on the quality time spent driving his Pontiac was not an option. With 3.42 gears in his Goat, relief in the form of an overdrive was in order.
Shearon decided to seek the advice of Bryan Blocker at Blocker's Performance and Restora-tion (Vilonia, Arkansas). After considering sev-eral options, Shearon did the math. You see, when he multiplied 2x3 he came up with a Gear Vendor's overdrive unit to install on his Turbo 400 transmission.
The lightweight, compact unit bolts directly to the back of the existing Turbo 400 transmission and allows each gear to be overdriven. Thus, a three-speed automatic can now become a six-speed.
This offers three major advantages to the classic Pontiac owner. One is the benefit of the 0.78 overdriven final gear, lowering highway rpm and allowing greater fuel economy. The second is allowing the use of higher numeric gears for better performance on the street and at the track. And the third is the ability to split the gears to provide close-ratio gear changes for improved acceleration.
Based in El Cajon, California, Gear Vendors has been supplying its overdrive devices for vehicles ranging from hot rods to motor homes. While not inexpensive (ours cost $2,395 for PN 3D0400FS), they are a proven alternative made to withstand the abuse of high-horsepower, high-torque engines.
The installation in the '68-'72 GTO is not a true bolt-on procedure, as you'll see in this article. Gear Vendors warns users up front that mounting the unit will require the installer to "massage" the floorpans around the transmission tunnel and shorten the driveshaft. Depending on the application, some changes might be needed on the transmission crossmember as well.
"Massage" means using a big hammer to round out the transmission tunnel from the front seat belt anchors forward to accommodate the unit. If you are reluctant to alter the originality of your car, this might not be the solution for you. The good news is, the section of the tunnel that is pounded out is concealed by the seats and console and is difficult to spot from inside the car. It looks mostly stock from the underside as well since the tunnel shape is only rounded out more.
Inside the car, you must mount the control head for the unit. This allows the driver to select the fully automatic overdrive that works like a modern four-speed automatic, or set the transmission to be manually shifted from one overdriven gear to the next. The latter is achieved via a floor-mounted switch just like the floor-mounted headlight dimmer switch, or you can add a shift button on your aftermarket shifter where the driver presses the button to make the shift.
The instructions for the kit are straightforward and complete. If an installer should have a problem, a tech line is available. Gear Vendors was helpful when we called regarding the proper installation of the speedometer plug.
Gear Vendors supplies a complete...
Gear Vendors supplies a complete kit with concise and informative directions. There is also a toll-free tech line should you encounter problems.
The first step was to remove...
The first step was to remove the existing speedometer cable and retaining bolt for the stock speedometer gear. Both will be discarded. The Gear Vendors kit supplies a plug to be used in the end of the speedometer gear housing, and it will be bolted back on to retain the transmission fluid.
Bryan Blocker of Blocker's...
Bryan Blocker of Blocker's Performance and Restoration then removed the transmission mounting bolts and raised the Turbo 400 with a transmission jack. Once the weight of the unit was off the crossmember, it was removed. For cars with a tight fit, the exhaust might need to be unbolted at the manifolds to allow room to remove the crossmember.
The six bolts that retain...
The six bolts that retain the stock transmission tailshaft housing are unbolted, and it is removed. Blocker recommends a few taps with a rubber mallet if it is stubborn and does not want to break loose. Be careful, since this is an aluminum housing and can be cracked or broken easily.