To make the checking of the...
To make the checking of the overdrive unit's fit easy, an empty dummy case was used. Do-it-yourself installers would just swing up the McCoy.
Breaking from our usual jack-it-up-in-the-driveway install, when Rick Johnson of Gear Vendors offered to install the unit at the factory, we figured we'd check out their production plant and let them handle it. We set an appointment at the Gear Vendors facility near San Diego, about an hour and a half of freeway time from our digs in Los Angeles. Driving down, we decided to take the desert highway route to avoid traffic. Settling in the fast lane at our cruising rpm of 3,500 rpm, the Charger soon began bottling up the high speed desert freeway traffic. Trying to keep up with the assorted mini trucks and Hondas coming up on our tail, we edged the tach up to about 4,000 rpm, and they still kept coming. Finally, looking in the rearview, we saw a guy in the service van behind us throw his hands up in disgust. We gave up, moved over to the slow lane, and dropped it down to 3,500 rpm for the rest of the trip.
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.
|Gear Ratio Chart: Torqueflite 727|
|Trans||Ratio|| ||Final Drive Ratio|
Some massaging of the floorpan...
Some massaging of the floorpan was indeed needed in one spot to give adequate clearance at one stud on the upper right. Nothing serious here; it was taken care of with some quick work of an air hammer with a flat plannishing tip.
The speedo is read off the...
The speedo is read off the output shaft of the overdrive to register. A compact 90-degree adapter is utilized to make the best use of the available clearance. Calibrating the Gear Vendors' speedo drive ensured our speedo would be right on.
Bolted up, the compact Gear...
Bolted up, the compact Gear Vendors' overdrive tucks nicely in the driveline tunnel. Our muffler shop-bent exhaust pipe just cleared the corner of the unit. Any contact with the exhaust, chassis, crossmember, or floorpan will transfer vibration, so make sure everything clears as it should.
Next, the trans mount. The...
Next, the trans mount. The ears at the upper corners of the crossmember's mounting bracket kissed the adapter extension's mounting pad. Clipping the corners of the ears fixed that.
The mount went in for a trial...
The mount went in for a trial fit, and a check of the engine/trans angle. The unit had to come down slightly at the tail to preserve the stock angle.
Adjusting the angle was accomplished...
Adjusting the angle was accomplished by redrilling the crossmember tabs for the trans mount's lower cross bolt (arrows). Bolt in the mount, and make sure there is clearance between the crossmember and extension, since they are closer together with the redrilled holes. Ours just cleared, but otherwise, clearance the crossmember or lower rib of the extension as required.
The driveshaft was sent out...
The driveshaft was sent out to be shortened, the supplied new 1350-series yoke installed, and then balanced.
The last step is to hook up...
The last step is to hook up the Gear Vendors' electronic controls. We had the auto/manual mode switch mounted under the dash (arrow), while the manual control switch we used was floor mounted. That's it, bang shifts and drive on.