Gear Vendor's Overdrive - Mopar How-To! 3+1=6

The actual installation of the Gear Vendor is simplicity in itself. The original tailhousing is pulled off the back of the 727, and the Gear Vendor's adapter is bolted in its place. The adapter is flanged to bolt onto the 727 case at one end, and at the output side is flanged to receive the overdrive unit, placing it in position to engage the original output shaft through a short splined coupler. Some massaging of the driveshaft tunnel with an air hammer was all that was required to give adequate clearance for the compact overdrive unit-an area about 3-inches wide by 1 1/2-inches tall on the right side of the tunnel.

With the overdrive bolted in, the drivetrain angle was adjusted back to the stock specs (measured earlier), and the trans secured using the stock crossmember with a few minor modifications. Since the adapter/overdrive assembly replaces the stock tailhousing, the speedo drive is provided for in the overdrive unit. A compact 90-degree adapter was needed for our Mopar application, and the Gear Vendors' technician calibrated it for our gearing and tire size. With the Gear Vendors unit now hanging off the back of our 727, the driveshaft was then shortened. To finish the job, the Gear Vendors' electronic control package was installed, which provides for full automatic operation of the overdrive unit, while allowing the overdrive to be switched off or used in a full manual mode through an auxiliary switch. For the manual control, we went with their recommended floor mounted switch, although all manner of shifter- or steering-wheel-mounted switch gear can be used.

On The Road
With the hardware in, we rolled off the rack, and Rick took the wheel to show us the Gear Vendors' overdrive in action. Just cruising in automatic mode, the electronic control shifted the 727/Gear Vendor combo as though we had a factory four speed automatic down below. In automatic mode, the Gear Vendor-equipped tranny provides four shifts, with overdrive automatically kicking in at the programmed automatic shift point in the Gear Vendors' electronics package, typically 47 mph.

Once on the open highway, in automatic mode, the overdrive is already on by the time you reach freeway speeds. RPM at a high speed cruise was down from 4,000, to just under 3,200 at 85 mph, and about 2,700 at 70 mph-perfect. This is just where it needed to be to work efficiently with our torque converter, yet leaving plenty of revs available should the need arise. Remember, with the overall higher gearing effect of the overdrive in action, the run from 3,200-4,000 rpm is worth a 28 percent higher mph gain than with the direct drive ratio at work. Stabbing the throttle at speed, we got something we didn't expect, as the tranny kicked down to Second Over, and the Charger rocketed up to well over triple digits before shifting to Third Over. Without the Gear Vendors, top speed for grabbing an automatic kickdown had been about 65 mph. With the overall gearing effect of the overdrive engaged, we now had an extra passing gear-automatically-into Second Over at a 28 percent higher road speed. Very impressive.

We pulled off the freeway. It was time to put the Gear Vendors' unit through its paces in manual mode. There are now 6 forward speeds available: First, First Over, Second, Second Over, Third, and Third Over. With the TorqueFlite's wide gear ratio spreads, and the moderate ratio of the Gear Vendor, there is no overlap in ratios, with each intermediate range providing a useful gear split. The ratios run sequentially from first as follows: 2.45, 1.91, 1.45, 1.13, 1.00, and 0.78. With our blessing, Rick nailed the throttle, and proceed to bang through all six ratios. "Outrageous." That's the only way to describe 440 cubic inches screaming through six closely spaced ratios. He'd obviously done this a few times before. Rick told us that because the engine stays near the peak of its power curve, drag race users typically see meaningful ET gains, usually shifting in the First, Second, Second Over, and Third, firing that extra torque multiplication where it's needed most, between the two-three shift (First Over will usually blow-off the tires in a fast drag car)

Taking the wheel, we found getting the most from the Gear Vendors overdrive in manual mode takes a bit of practice. The actual shifts are tire-chirping quick, but with a slight delay from the moment the button is hit. Upshifting from an overdrive ratio to the next higher gear in direct, such as First Over to Second Direct, or Second Over to Third Direct, you have to hit the switch to kick-out the overdrive while slapping the shifter to the next higher gear. The thing you don't want to do is kick-out the overdrive before the tranny gears up, or you'll be going down half a gear instead of up. With a little practice, being conservative, and upshifting first, the feel for the shift timing will come, and then it becomes almost instant. Even sloppily done, the vehicle is under full power acceleration while all the shifting is taking place. It didn't take long until we were able to pull off the rapid-fire six-gear change show with the best of 'em.

With its gear-splitting ability, high-speed kickdown, and powerful upshifts, the Gear Vendor delivered more than the simple overdrive we expected. There was genuine performance to be found in the unit, beyond the bonsai-run ability and reduced engine wear and tear we sought. The thing is downright fun. With the demo over, we packed our gear for the long drive home-rightfully in the fast lane this time.