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.
After the unit was properly...
After the unit was properly seated, we torqued each nut in a cross-pattern to a very light 9 ft-lb of torque; do not over tighten these small studs.
With the overdrive unit installed...
With the overdrive unit installed on the tailshaft housing, we installed the transmission crossmember and removed the transmission jack.
We ordered the optional push-button...
We ordered the optional push-button shift knob with our kit. After a little wiring, a push of the button engages the overdrive.
The wire leading to the shift...
The wire leading to the shift knob could simply be tie-wrapped to the shifter handle, but we decided to cut a groove in the shift handle to act as a channel for the wire.
After cutting the groove with...
After cutting the groove with the cutoff wheel, the groove received a thin bead of black silicone before we pushed wire down into the groove. Masking tape holds the wire in place overnight for a full cure.
The next day we reinstalled...
The next day we reinstalled the handle and shift knob assembly along with the boot. The wire is nearly invisible on this very sanitary installation.
The Gear Vendors overdrive...
The Gear Vendors overdrive requires a larger front driveshaft yoke. We installed the yoke in the overdrive unit, allowing 5/8 inch of endplay. Then we made our measurement and took the driveshaft to Universal Service in Charlotte, North Carolina.
The good folks at Universal...
The good folks at Universal Service shortened the driveshaft and installed the new front yoke using a Spicer #3-3140 universal.
The driveshaft was slipped...
The driveshaft was slipped into the new overdrive unit, and then the driveshaft was attached to the differential with U-bolts.
With the driveshaft in place,...
With the driveshaft in place, it’s time to fill the overdrive and the main transmission with gear lube. Don’t forget to fill both units!
The wiring is really simple;...
The wiring is really simple; we mounted the Gear Vendors Control Box in the driver-side kick panel and provided a 12V keyed power source. A quality ground was also provided to the ground terminal on the box.
The overdrive lights were...
The overdrive lights were discreetly mounted in the Vintage Air underdash ducts for a tidy look.
As per the directions, power...
As per the directions, power was supplied to the solenoid that activates the overdrive unit.
A hole was cut in the Fatman...
A hole was cut in the Fatman Fabrications chassis crossmember to facilitate connecting the speed signal sensor. This same hole was used for routing the solenoid wiring.
With everything connected...
With everything connected you can see there is ample room in the frame for the Gear Vendors unit. The fill plug is on the top right, while the smaller bolt face on the lower right is the drain plug.
The signal sensor was mounted...
The signal sensor was mounted to the floor and is ready to accept the speedometer connection. This Smokey Yunick tribute car has no speedometer, relying on tachometer readings instead.
And here is the finished product....
And here is the finished product. The Gear Vendors overdrive unit fits perfectly in the Fatman chassis, and the gear reduction provides cruising at 50 mph at 1,650 rpm and 75 mph at 2,460 in overdrive. Without overdrive the same speeds arrive at 2,000 and 3,000 rpm, respectively.
Looking to all the world like...
Looking to all the world like a race car, the Fatman Fabrications Smokey Yunick tribute car is now truly a dual-use vehicle that works well on the highway or at the track.
The Gear Vendors overdrive was up to anything the 427 ci of small-block Chevy power could dish out on the highway, dragstrip, or autocross.