Nothing says horsepower quite like rowing through the gears in a 1960s vintage, big block-powered muscle car. But like all good things, there is a price to be paid for mechanical nirvana. The acceleration-oriented rear axle gears in many muscle cars can put the hurt on top-end speed (not to mention fuel economy), and the 3,000-rpm drone at highway speeds sure puts the hurt on your ears on long distance road trips.

But there is a way to enjoy the rush of a manual transmission without the speed and sound penalties: An overdrive transmission. With a five- or six-speed manual box, you get the acceleration benefits of that big rear axle gear, plus the ability to hit those big mile-per-hour figures and cruise at diesel-like rpm at highway speeds.

So why isn’t every four-speed muscle car owner rushing to stuff an overdrive transmission in their ride? Authenticity and restoration issues aside, there are two big reasons. Most overdrives are not a simple bolt-on proposition, and most OEM boxes cannot handle the torque output of a big block V8.

But thanks to Richmond Gear’s six-speed transmission, these problems are surmountable. The Richmond box has features that make it perfect for use in a 1960s-era car:
• 450 foot-pounds torque rating
• All aluminum construction—weighs just 108 pounds
• Wide range of gear ratios available—can tailor transmission for virtually any application
• Versions for popular GM, Ford, and Mopar input spline counts and bellhousing patterns

The standard Richmond box comes with 3.27 (1st), 2.13 (2nd), 1.57 (3rd), 1.23 (4th), 1.00 (5th) gears and your choice of a 0.76, 0.81, or 0.86 ratio 6th gear. But since there are dozens of other ratios available, you can tailor the transmission for specific applications—road racing or long-distance touring, for example.

Not long ago, a friend of ours wanted a Richmond box for his 1969 Charger R/T. The Charger has a 492 cubic inch stroker 440, a Hemi-spec A-833 four-speed, and 4.10 rear axle gears into the factory 440/four-speed car. The combination produces neck-snapping acceleration, but conks out just shy of 120 miles per hour—and turns at almost 3,200 rpm at 65 miles per hour in fourth gear.

To better match the intended use of the car, a six-speed with a 3.04/2.13/1.57/1.24/1.00/0.76 gear set was added, along with a 3.33 ratio gear (a rare piece, by the way) for the Dana 60 rear axle. This combination matches the original A-833 four-speed’s gear ratios in terms of acceleration, allows much higher top speeds, and lets the big block loaf at less than 2,000 rpm at 65 miles per hour in sixth gear.

While the Richmond box is about the same length as GM’s Muncie and T-10 four speeds, installing it in the Charger was not a simple bolt-in. The Richmond’s case is almost 10 inches shorter than the A-833’s, requiring a longer driveshaft. The Richmond’s shifter location is seven inches further back than the factory shifter. While this puts the shifter in a much better position (the factory location is too far forward for powershifting), floorpan and crossmember modifications are required to get things to fit.

Even though it was no walk in the park, the benefits of installing a Richmond six-speed in a classic Mopar muscle car are well worth the effort. There were no kits available when we documented this swap, but today companies like Keisler Automotive Engineering offer swap kits and components to make the job easier. When you can get 1960s-style acceleration, awesome high-speed capability, and the ability to hold a conversation at highway speeds in one package, you better grab it quick.

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transmission for a car prior to installation
clutch pack installed under a car
tailshaft view of a transmission under a car
measuring for a transmission swap
cutting section of a car floor for transmission access
installing a transmission crossmember
transmission mount and transmission
modifying a bellhousing for a car
transmission in car from above with floor removed
transmission installed in car
sheetmetal floorpan parts
floor shifter installed in an old car
vehicle driveshaft transmission tunnel
man holding a car driveshaft
manual transmission installed in an old car
speedometer cable installed in a drive housing
man shifting an old car

The all-aluminum Richmond ROD six-speed weighs a mere 108 pounds, and is compact enough to fit in virtually any American muscle car. But the biggest advantages are the two extra gears (sixth is overdrive) and the ability to tailor the gear set to specific drivetrain combinations.

The Richmond transmission comes with an 18-spline input shaft. Fortunately, the A-833 in the Charger was the heavy-duty version with the same spline count input shaft, allowing the existing Centerforce Dual Friction Clutch and Hays Flywheel setup he already had.

Because the Richmond six-speed's shifter location is further back than the A-833's, the front crossmember had to be modified to clear the shift linkage. That was not a small matter since the crossmember is a major structural component that supports the front subframe. The Richmond box uses a GM style transmission mount, so the stock transmission support needed to be modified as well. The yellow lines show where the floor pan will be cut for shifter clearance.

With the transmission in place, we measured for the new driveshaft. The Richmond six-speed is approximately three inches shorter than the old A-833, thus the new driveshaft would need to be 54-1/2 inches long.

Restoration purists should avert their eyes at this point. Brian cuts the transmission tunnel and floor pan to make room for the Richmond's shifter linkage. He will be building new pieces to cover that big hole.

This photo clearly shows how beefy the six-speed's shifter body and the shifter linkage are, and where the transmission support will need to be modified for clearance.

We used a polyurethane Energy Suspension GM transmission mount, which fits to a bracket welded inside the trans support. The yellow marks indicate how much more floorpan needs to be removed to clear the linkage.

The Lakewood bellhousing had to be modified slightly to fit the Richmond box. The pointer indicates the boss welded in for the additional mounting hole near the clutch fork access hole. The transmission now bolts right up to the bellhousing.

Here is the Richmond transmission in its final mounting position. The hoop is a piece of two inch wide, ¼-inch thick steel Brian welded in to replace the part of the front crossmember he cut out previously.

This is what the finished crossmember looks like under the car. We welded the hoop to each end of the crossmember and drilled two new mounting holes for the transmission support. Note the Energy Suspension transmission mount.

Brian made these new floorpan pieces out of 20 gauge sheetmetal that came from, of all things, the roof of a Pinto station wagon. The piece at lower left covers an access hole on the passenger side of the transmission tunnel. These pieces are now available as reproductions.

Looks stock, doesn't it? Here is the completed floor pan/transmission tunnel sheetmetal, coated with epoxy paint. You can see how much further back the Richmond's shifter is from the factory shifter position.

Here is what the completed transmission tunnel and crossmember look like from underneath. Any gaps will be filled with silicone, and everything will be sprayed with epoxy paint and undercoating for maximum rust resistance.

The chromoly driveshaft is tougher and less prone to flex than a stock mild steel or an aluminum driveshaft. But at 14 pounds (with yoke) it's just a couple of pounds heavier than an aluminum shaft.

Here is the Richmond six-speed in its final resting place. Once the shift linkage is hooked up, our friend will be able to shift the 492's 540 horsepower and 600 foot-pounds of torque back to the 3.33-geared Dana 60.

Were you wondering how the speedometer cable was routed? We drilled a hole in the crossmember to snake the cable through to the transmission. This allows the cable to go up through the floor and to the dash without kinking. New carpeting will cover up the cable.

With the old A-833 four-speed, the shifter was 7 inches farther forward, requiring a 14-inch-long handle. With the four-speed and 4.10-geared Dana 60, the Charger pulled like a freight train but howled at 3,200 rpm at 65 miles per hour. With the Richmond six-speed, the car still rips through the gears, but is now capable of doing 190 in sixth gear, and cruises at a leisurely 1,974 rpm with a mild 3.33 rear gear.

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Parts List
Richmond Gear Six-Speed Transmission, 3.27/2.13/1.571.23/1.00/0.76 gear ratios (RMG-7021618AA)
Lakewood Bellhousing (LAK-15330)
Hays Billet Steel Flywheel (HAY-11-430)
Energy Suspension GM Transmission Mount, Black (ENS-3-1108G)