There was a time when the dual-purpose car was the norm rather than the exception. Driving your hot Chevy to work all week and racing on weekends was a way of life for many hot rodders. As the competition got tougher at the racetrack many dual-purpose cars were forced to choose, street or strip. This brought about an onslaught of dedicated race cars. One of the defining reasons for the death of the dual-purpose car was the final drive gear. To be competitive at the track you need a low final gear, while driving to work you were wishing for a tall gear.
Enter the overdrive, a system that was popular in the ’30s through the ’50s but most overdrive transmissions, including the ancient Columbia two-speed rearend, were not up to the rigors of racing.
When Brent Vandervort of Fatman Fabrications decided to build a tribute car of the old Smokey Yunick ’57 Chevrolet, he knew it would be a four-speed car like the original. It’s not a faithful reproduction of the famed No. 13, rather a tribute car that embodies the spirit of the original with plenty of horsepower in a relatively basic ’57 sedan. Underhood, a potent 427 small-block stroker motor fills that requirement. At first the car was enjoyed on the street, hitting a lot of street rod–style events and local cruise nights and then the autocross challenge came into the picture. Competing at a number of autocross events has become very popular and after a few passes it became obvious the car needed a much lower rear gear.
The problem with changing to a 4.11:1 gear was Vandervort is still an avid enthusiast and that means he drives his hot rods. It was obvious the dual-purpose car was back, but luckily today there are options to allow you to drive a long distance to an event, and then, with the flick of a switch, convert to a race gear. Enter Gear Vendors’ Overdrive.
This unit couples to your existing four-speed or automatic transmission and can handle the horsepower and torque of big-horsepower powerplants; interestingly, Vandervort was originally introduced to these units several years ago when he installed one on the company truck for towing. The unit proved to be trouble free, tough, and effective. More recently, a call was made to Gear Vendors and the following week we were at Fatman Fabrications helping to unpack one overdrive unit.
The Gear Vendors unit is compact, well engineered, and relatively simple to install. Other than shortening the driveshaft, fabrication is minor and the installation is well within the abilities of your average enthusiast.
Vandervort builds his hot rods the old-fashioned way; if he has something on hand he uses it, and that explains the Ford Top Loader four-speed mated to the 427ci small-block. Once again, no problem for the team at Gear Vendors, they sent all the right pieces to mate an overdrive to the rear of the Top Loader.
The entire process can be completed in a weekend, and while our ’57 rides on a complete Fatman Fabrications reproduction chassis, the compact Gear Vendors unit will generally fit most factory frames without serious modifications. We found our kit to be very complete and only left the shop to have the driveshaft shortened along with purchasing the new front universal, in order to mount the new yoke that was supplied with the kit.
The wiring for the electrical controller was straightforward and the supplied gearshift knob activates the overdrive with a quick push of the button. The kit even comes with indicator lights to advise the driver when the overdrive is engaged, although we’d like to think our readers are aware enough of the tachometer to not be looking for the light.
Shortly after the installation was complete, several of the Fatman Fabrications employees headed down to Atlanta Dragway for the Chevy High Performance Nationals. The overdrive unit performed flawlessly on the road and proved it could handle the power on the dragstrip until there was no power to handle. Unfortunately, the 427 came apart during the final pass on the dragstrip and prior to the autocross event.
And so the dual-purpose hot rod is back, but unlike the “good old days”, today there is any number of ways to drive to the track at highway speeds and compete when you arrive. Gear Vendors’ Overdrive is one such option, so let’s get busy with the installation.