We here at Power Automedia are soon to be revealing the newest addition to our project car lineup —a 2014 Camaro SS that’s been christened the “Copo Clone” by our staff — that we plan to transform from a stolen 5th gen into a bad ass True Street ride flirting with high 8-second performances. The Copo Clone will be a street-driven tribute car of “sorts” and will be motivated by a Chevrolet Performance LSX376-B15 powerplant (a boost-capable crate engine from Chevy Performance) fed by a Whipple supercharger, with a goal of exceeding 1,000 rear wheel horsepower and pushing the SS into True Street contendor status.
Of course, making that kind of horsepower is only half the equation, as we also must efficiently transfer it from the flywheel to the third member out back. With affordability, consistency, and ease of maintenance all part of our goal with this project, the use of a standard issue two-speed GM Powerglide was almost a no-brainer. And so we teamed with our friends at Hughes Performance in Arizona, one of the leaders in drag racing drivetrain technology, to help us match the boosted bullet with a more-than-adequate transmission and torque converter combo suited for the power, torque, weight, and style of racing that we’ll be doing.
Why A Powerglide?
The Powerglide transmission has long been a favorite of drag racers, particularly the bracket racing crowd and other low-budget competitors. First developed and equipped on Chevrolet vehicles in 1950, the since-discontinued automatic transmission has become a staple thanks to it durability and simplicity. And because it’s use is so widespread, aftermarket parts are a dime a dozen, making it even more attractive to racers, even nearly four decades after it was last produced.
An overdrive 4L80E, while providing us the best of all worlds if we wanted to do street/strip duty, would require a fairly hefty weight penalty, making the Powerglide an obvious choice for our needs as a race-only vehicle.
They’re durable, with relatively minor initial investment. They’re very affordable racing transmissions to get into, and having a two-speed transmission makes the car more consistent and easier to drive.
Nichols continues, telling us, “the Powerglide is also lightweight with relatively low rotating mass, so there’s not a lot of parasitic horsepower loss there. With a Powerglide, compared to something like a three-speed, you’re going to effectively deliver more horsepower and torque to the rear tires.”
The Powerglide Build
No two race cars are the same, and that means that vital components like transmissions and torque converters are rarely one-size-fits-all or one-size-fits-most. Detail-oriented manufacturers like Hughes Performance cater their products to the specific needs of their customers, based on a large number of variables, some of which (and we’ll get into this later) will surprise you, from the basics of power, weight, gear ratio, and tire size, to such nitty-gritty things as camshaft lift, duration, and lobe separation, maximum RPM, connecting rod length, bore and stroke, intake centerline, runner volume, header tube diameter, and more, which all play into the power curve of the engine.
We sent Nichols and the Hughes team a thorough list of specifications on the Camaro, down to the last details, to help them formulate just the right setup for our pet project.
Because they offer so many options, Hughes builds each of their Powerglides to-order, maintaining a wide-ranging stock of part numbers that fit particular vehicle combinations, with horsepower, torque, weight, and the tire being the key elements in what components are selected for the transmission build.
“It’s not so much a custom one-off build as much as it’s selecting the right components that we’ve already developed and that we know works for a specific combination,” says Nichols. “Our transmissions carry horsepower ratings that are good, safe ratings that are generally conservative, but there are exceptions to every rule, where you have a unique combination that does need something stronger, even though the vehicle isn’t producing that advertised horsepower.”
“OEM transmission cases are generally reliable up to 1,500 flywheel horsepower, although that rating can vary depending on a number of factors, including torque production, how the transmission is going to be used, and the type and quality of chassis that the transmission is being installed in,” explains Nichols.
It’s not so much a custom one-off build as much as it’s selecting the right components that we’ve already developed and that we know works for a specific combination.
With the core of the transmission ready, now it gets a little more in-depth.
Starting at the rear of the case, Hughes installs a new bushing to support the output shaft, then adds -6AN male fittings in the cooler ports on the passenger side of the case. An extension housing is prepped in the same way as the case, and a new bushing for the slip yoke and a new lip seal are installed. The original stator tube is pressed out to prepare for the new front pump, and a Hughes’ own heat-treated, heavy duty stator tube is installed into the pump stator. According to Nichols, this premium stator essentially eliminates the possibility of twisting the stator spline.
Hughes then moves on to resurfacing the pump stator to ensure the sealing surface for the pump body is flat and true — a step that is critical, as a warped pump stator can lead to front pump cavitation, internal leaks, cross leaks, and torque converter fluid starvation.
The pump body is then lapped to create a true and flat surface and a new pump bushing, lip seal, and pump gears are installed, with clearance between the pump body and pump gear set checked for accuracy. Following this step, we arrive at the input shaft, which in our build is a 30-spline Turbo Spline, made from Hughes’ proprietary billet steel alloy. This shaft sports unique round Teflon sealing rings that allow for reduced depth cuts without stress risers to be made in the input shaft to accept the sealing rings, which contributes to better input shaft durability.
The transmission features an eight clutch high gear drum, with heavy duty red racing frictions and standard non-coated steels that are standard in all of Hughes’ Powerglide builds. This clutch drum setup is suitable for up to 1,500 flywheel horsepower, but has powered vehicles in the 1,700 to 1,800 range. The high gear clutch hub is made from 9310 billet steel.
Hughes installed their proprietary, Extreme Duty bands in the transmission, which has a unique lining with a high coefficient of friction for maximum holding ability in low gear. A 1.76 billet planetary set was also chosen for the build, with gears made in-house from billet steel alloy. The gear set is installed in Hughes’ own 4340 forged steel carrier and output shaft assembly using case-hardened pins and special thrust washers to reduce friction.
Six heavy racing frictions and standard, uncoated steels are installed in the reverse clutch pack.
During front pump assembly, Hughes Performance machines the back side of the pump stator to accommodate the increased thickness of the bearing that rides between the back of the pump stator and the front of the high gear drum. Some methods involve instead machining the face of the high gear drum, but doing so reduces the depth of the sealing area inside the high gear drum, potentially causing the front sealing ring to lose seal, creating an internal leak, loss of pressure, and outright failure of the band or clutch pack.
Moving down below, the deep cast aluminum pan that’s been selected holds two additional quarts of fluid compared to an OEM steel pan, and has a drain plug for easy servicing. Hughes also uses a screen-style filter element in all of their builds. Says Nichols, “Some builders prefer installing a 727 Torqueflite filter typically manufactured from Dacron material. Contrary to popular belief, the Torqueflite filter is actually restrictive and will contribute to front pump cavitation and potentially starve the torque converter for fluid. A screen-type filter element is far superior.”
After the reverse clutch packs and planetary assembly is in we move to the high gear drum. The input gear for the planetary gear set is attached to a flange that’s installed into the high gear drum during the drum’s final assembly. Hughes’ technicians apply 120 psi to the high gear drum to verify that the clutch pack applies properly and to ensure that no leaks are are evident before installing the full drum assembly into the transmission case.
The next step in the process is installing the servo into the case. Hughes manufactures their own billet aluminum servo, which sports dual sealing rings to minimize fluid leakage past the servo to maximize pressure against the servo. Hughes uses a specially calibrated servo return spring to provide a quick release at the 1-2 gear change. Moving on, we arrive at the installation of the band, including the band adjustment screw, band apply struts, and the band itself into the case.
At this stage, Hughes performs final assembly of the front pump. A special steel band tool is used to align the pump halves before torquing the fasteners to spec. Once assembled, Torrington roller thrust bearings and premium Teflon sealing rings are installed on the pump stator. Now, the front pump and input shaft are installed, and 120 psi is applied to pressure test the servo apply port to ensure the servo applies the band properly. The application of the reverse clutch pack is also tested.
Next, the internal shift linkage and parking mechanism are installed, along with an aftermarket manual shaft and shift arm, which is done on all Hughes Powerglide builds. This is followed by installation of the valve body, filter, and pan, along with the governor support, which sports a new bushing to help support the output shaft. With that, the build is virtually complete, and it’s on the transmission dyno.
Every transmission that goes through Hughes Performance is tested to verify function, line pressure, and transbrake operation. This test breaks in the transmission so the unit is ready-to-race, right out of the box. As Nichols shared with us, all of the Sportsman, Pro Series, and Pro Mod Powerglides are set up to operate at 245-255 psi line pressure, and in general, Powerglides should never exceed 275 psi to avoid possible bending of the band struts and all out band failure.
The torque converter that we’ll be pairing with the transmission is a custom 9.8-inch Hughes’ Pro Series Heads-Up Radial Tire unit, part of a relatively new lineup of converters that have been designed specifically for small-tire doorslammers. These converters sport unique impeller and stator designs that contribute to maximum acceleration potential (G-force) without overpowering radial, True 10.5, 8.5-inch slicks and similar tires. Not only that, but they’re intended to be very efficient, with as little as 1.5 percent slippage during a quarter-mile run.
“There are a few different converter cores that we use in our Radial Tire series, and it’s really about the stator design, which is one of the most influential components of how the converter functions,” says Nichols. “We’ve developed a family of stators within that converter series that help manage the ‘hit’ at the starting line and manage the torque multiplication. This makes it much easier to launch cars with a very limited tire.”
We’ve developed a family of stators within that converter series that help manage the ‘hit’ at the starting line and manage the torque multiplication. This makes it much easier to launch cars with a very limited tire.
Our converter was hand-built with a furnace brazed and silicone spot brazed impeller assembly and turbine assembly, a heat treated billet steel turbine spline, heat treated forged steel pump, full roller bearings, anti-ballooning plates, a custom designed, CNC-machined billet aluminum stator, and Extreme Duty sprag assembly with oversize rollers and heat treated races, and a CNC-machined billet steel cover with six-lug mounting. It has dual bolt patterns (3 x 10.75” and 3 x 11.50”) with 7/16”-20 threads) and an extended torque converter pilot for compatibility with the LS engine.
The billet aluminum stators that Hughes uses in these converters are custom designed for specific applications, and have been used in drag racing combinations with upwards of 3,800 flywheel horsepower and gross weights over 3,200 pounds. We’ll never scratch those kind of horsepower numbers, but we’re right there on weight.
Hughes uses custom machined stator caps with wide channels for maximum fluid flow in and out of the converter, which prevents fluid starvation and cavitation within the converter.
In the final assembly process, the converter is welded together and, like the transmission, goes through a final check for run-out, is pressure tested, and then balanced once it passes the first two phases. Once balanced, the converter is painted, boxed, and sent out the door for us to install in our brand new project ride.
As you’ve read here and seen in the photos, Hughes Performance has definitely done their homework on their transmissions and converters, bringing to the table decades of engineering, trial and error, and field testing with every drag racing combination imaginable to make matching their products to a specific vehicle, engine, and tire a virtual art form that even we can’t wrap our minds around. And we’re certain that we’ll see the fruits of their labor when our Camaro hits the track running in the future. We hope you’ve enjoyed this behind-the-scenes look at this build as much as we’ve enjoyed bring it to you. Until next time…