The Powerglide transmission is undoubtedly the most widely used transmission in all of drag racing, and has been used behind everything from mild street-strip cars to wild 3,000-plus horsepower Pro Modified cars running the quarter mile in well under six seconds.
If you’re anything like us, you may have wanted to know how an automatic transmission is able to survive behind that kind of horsepower. Is the transmission anything like the transmission in a typical bracket race car, or is it something completely different?
In this article we’re going to examine the differences between a Pro Mod Powerglide transmission and your more bracket race Powerglide. For that, we enlisted the expertise of J.C. Beattie Jr. of ATI Performance Products to help us explain the technical aspects of both transmissions.
“The functionality of the transmissions are the same — both are two speed transmissions plus reverse. A single low gear set and a single high gear drum with clutches.” – J.C. Beattie Jr.
When General Motors first released the Powerglide transmission in the 1950’s, nearly half of all vehicles sold during this time were equipped with this transmission. This popularity among new car buyers help to infuse the Powerglide into the world of drag racing since there was an abundance of transmissions and parts available at the local junk yard during the 1960’s and 70’s.
Now-a-days, it is getting very hard to find OEM replacement parts for a Powerglide transmission in a salvage yard like racers could do in the past. In order to support racers with transmission parts for entry level transmissions as well as the high-end units, companies like ATI Performance Products have developed a full line of Powerglide components to support virtually any power level or application.
Why We Love the Powerglide
The Powerglide transmission has been a long time favorite of the bracket racing crowd due to the simplicity of the transmission and the lightweight design. According to Beattie, the Powerglide transmission also requires a third less power to run when compared to conventional 3-speed transmission, thus making it very efficient at transferring power to the wheels. Since the Powerglide is very popular among racers, the price of components is also very reasonable due to the mass production of components and accessories related to the transmission.
In recent years, high horsepower racers have started to move towards lock-up torque converters in an effort to put every last drop of power to the ground. This has helped racers like ATI flag-carrier Chris Rini reset the record books and propel automatic transmission cars deep into a territory once dominated by manual transmission cars.
The lockup torque converter is especially important in a Powerglide transmission since you are in high gear for a long time. The lockup functionality acts like a third gear. – J.C. Beattie Jr.
The most notable difference between a bracket race Powerglide and a Pro Mod version is the use of an aftermarket transmission case in the higher horsepower applications. In high-horsepower applications, the transmission is not only under a great deal of torsional stress from hard accelerations, the internal line pressure is nearly two times that of a stock transmission. According to Beattie Jr., “We typically recommend our SuperGlide 4 transmission when customers are making over 2,500 horsepower.”
The stock transmission case is manufactured from a die-cast aluminum process that is relatively brittle and when subjected to the high internal pressures and stress of a high horsepower application, can fracture. The die-cast process also allows for thin walls to be cast, thus saving weight for the manufacturer, and reducing overall cost. However, what you end up with is a thin-walled transmission that has a brittle material — not a good combination for high performance.
ATI uses a cast aluminum transmission case manufactured from 356 T6 aluminum for the ultimate strength in their SuperGlide 4 applications. This cast-aluminum transmission case was designed by ATI to be thicker in critical areas to handle the high stress loads of a 3,000 horsepower car pulling a sub one-second 60’ time. It’s also a modular design so the transmission bell housing is removable and is located on center to the pump bore.
“We re-use less than 1% of the OEM Powerglide parts in their SuperGlide 4 transmission, while the majority of the remaining components are machined from billet bar stock,” according to Beattie Jr.
A bracket race Powerglide would use a stock diameter input shaft that is a little smaller than one-inch in diameter, and made from standard 4340 or even 300M material. The input shaft was one of the limiting factors when racers first started to push the power limits of the Powerglide transmission, so it was determined that a larger diameter shaft was in order.
In order to handle the immense torque of a Pro Mod engine, the diameter of the input shaft had to be increased to 1-3/16”. Although this doesn’t seem like a substantial change, it required a larger diameter stator tube, billet pump assembly, support bushing, and two gears of the gear set to be redesigned. ATI claim that they were the first company to the market with a big input shaft Powerglide transmission, starting with the SuperGlide 3 in 2007. The torque converter inner race and turbine hub also had to be remade to accommodate this change.
The SuperGlide 4 is available with either a standard PG output shaft or the larger TH400 output shaft and most racers choose to upgrade their transmission to the TH400 shaft.
The difference between the gear set in a bracket race ‘Glide versus the Pro Mod transmission are like the differences between night and day.
A bracket race Powerglide would normally reuse the OEM helical gear set due to cost of an aftermarket gear set. According to ATI, helical gears are much quieter than straight cut gears, but they cannot handle the same power as the straight cut design since they’re typically not made from good material. An entry level bracket race Powerglide would typically reuse the OEM gear set carrier that’s manufactured from stamped steel due to cost. The bracket racer has a choice from two gear ratios from the factory — 1.76 and 1.82. The 1.76 gear ratio is the most popular choice since it’s capable of supporting the greatest amount of power while still using less expensive OEM components.
The SuperGlide 4 transmission uses a straight cut gear set that’s manufactured in-house at ATI from Vasco material. “Vasco material is typically used in applications that need the greatest amount of strength and impact resistance,” says Beattie. “It has a much higher tensile strength than 4340, 300M or 9310 steel, yet it maintains a higher elasticity so it will give before it breaks. It also carries a cost that is $5 more per inch than 4340.” In other words, the Vasco material is the strongest gear set material available to ATI, and can survive the instantaneous shock load of a Pro Mod car launching without breaking the gears. The SuperGlide4 also uses an optional billet aluminum gear set carrier that’s lightweight and bulletproof. The Pro Mod racer has the choice between multiple gear ratios ranging from 1.62, 1.64, 1.66, 1.80 and 1.82.
Clutch and Drum
One of the major differences between a bracket race Powerglide and one that’s built to handle the power of a Pro Mod car is the number of clutches and the quality of the clutch material. An entry level bracket race transmission uses 5-6 clutch discs in the drum, whereas the SuperGlide 4 uses 10-11 clutch discs to in just one transmission. ATI claims the SuperGlide 4 transmission uses the best clutch material on the market, so as you might have guessed, it costs more than your standard clutch plate. If you were going to replace the six clutches in a bracket race Powerglide, you might be out $18, but if you replaced all 11 clutches in a SuperGlide 4 transmission, be ready to fork over $220.
The transbrake functionality is similar between the Pro Mod version of the transmission and a standard bracket race Powerglide. When the transmission is in low gear, and the transbrake solenoid is energized, it applies pressure to the reverse clutches, which places the transmission in first gear and reverse at the same time. Once the solenoid is released, the pressure on the reverse clutches is released and the car launches off of the line.
Since the Pro Mod version of the transmission operates at a higher line pressure, there is substantially more pressure applied to the band when the transbrake is engaged. The SuperGlide 4 transmission utilizes an ATI machined billet aluminum, Wicked Quick valve body that’s roughly 0.02-seconds quicker on the release over conventional steel transbrakes, which allows the Pro Mod car to react quicker to the four-tenths Pro-Tree light.
Oil and Cooling
As you might have guessed, there’s a big difference between the valve body on a Pro Mod car versus what is used in an entry level bracket Powerglide. An entry level Powerglide uses a heavy cast iron valve body with stock passages that were designed for smooth shifting. Pro Mod transmissions utilize a billet aluminum valve body with optimized flow paths for the quickest shifts possible while saving precious weight. ATI uses a billet valve body in their SuperGlide 4 transmission and tops off this lightweight combination with an ultra-trick titanium bolt kit. The billet aluminum VB is nearly eight pounds lighter than its cast iron counterpart.
The bracket race Powerglide uses a stock-type pump that has an adjustable line pressure usually set at a maximum 180 psi, whereas the Pro Mod SuperGlide 4 uses a billet aluminum pump that delivers an impressive 300psi. With the added pressure of the billet pump, the transmission case and other internal components must be upgraded to handle this additional system pressure.The billet aluminum pump also has a larger diameter stator tube with increased wall thickness which enables a larger input shaft to handle the immense power and torque of a Pro Modified engine.
A bracket race Powerglide typically would be configured with an external transmission cooler if the racer is using a transbrake since the transmission will build up heat quickly when the ‘brake is engaged. If the bracket racer is using a foot brake model, there would be less of a need to run a transmission cooler because the system doesn’t build the heat as quickly as the transbrake variant.
Pro Mod racers on the other hand would prefer to not run a transmission cooler since it’s adding weight and complexity to the car. The Pro Mod racers typically tow their cars to the starting line and back so the engine is only running a couple of minutes per run. Since an automatic transmission does not pump any fluid when the engine isn’t running, Pro Mods needed another way to cool their transmission and torque converter between rounds.
Recognizing this unique need, ATI developed and patented the first integrated electric pump and cooler system known as the SCS-30, which allows the transmission fluid to circulate through the torque converter and a cooler when the engine isn’t running.Alternatively, racers may choose to forgo the transmission cooler in exchange for quick-disconnect fittings that enable the racer to connect an external chill box and pump to the transmission when back at the trailer.
Most entry level Powerglides are equipped with a stock type steel pan, whereas the high-end SuperGlide 4 uses an extra capacity cast or sheet metal aluminum transmission pan. Changing the transmission pan is one of the first upgrades most bracket racers do to their transmission since it helps with heat dissipation and is relatively cost effective upgrade.
The final part of the puzzle is the transmission fluid that’s being run in these transmissions.The bracket racing crowd, in general, runs conventional transmission fluid in their car due to cost, because it’s easier to change the fluid more often rather than buying the synthetic alternative.
The Pro Mod racer, though, can’t afford not to run synthetic fluid in their transmission since conventional fluid will break down under the extreme heat and pressure. ATI Racing developed their own blend of 100% synthetic transmission fluid based upon the Type-F transmission fluid that contains friction modifiers. With the help of Driven Racing Oils, the ATI transmission fluid allows the transmission to run cooler under extreme conditions, while providing the necessary friction for the clutch to function correctly.
ATI Customers Using The SuperGlide 4 Transmission
ATI currently has over 200 of the SuperGlide 4 transmissions in service and this record setting transmission has been installed behind everything from 3,500 horsepower Pro Modified cars to monster trucks and everything in between. Among those utilizing it in drag racing circles:
Chris Rini: The ATI Performance Products-backed Camaro has been a test bed for many ATI components, including the Lock-up SuperGlide mentioned within this article. Rini’s machine, which garnered the NMCA Pro Street championship a year ago, is powered by an 864 cubic inch big-block nitrous fed monster that has propelled this 2,350 lb. car to a best run of 5.95 at a blistering 245 mph and several laps in the threes in 1/8-mile trim.
Rich Bruder: Bruder has put the X275 drag radial class on notice with his dark blue Fox-bodied Ford Mustang. Bruder, who campaigns along with his brother Nickc, tuner Mike Modeste, and his family, uses an F-1X ProCharger on the small block Ford powerplant to put down an impressive best of 4.55 at 160 mph in the 1/8th mile. Rich and his team made this pass using the 2012 X275 rules using an ATI SuperGlide 4 transmission.
Billy Gordon: The Virginia native has been one of the front runner in Outlaw 10.5 over the last couple of seasons in his 2004 Ford Mustasng, which features a 632 cubic inch, twin turbo combination. Gordon has been 4.14 and 197 mph with the SuperGlide in his Mustang.
Jeff Lutz: The NMCA Pro Street competitor has been a serious threat to win at virtually ever stop on the series tour with his twin 88mm turbocharged, Pat Musi-built, 540 cubic inch big block Camaro. Lutz has been in the 6.0’s in competition and recently carded an impressive 5.91 at 249.72 mph in testing, as well as a 3.93 in the 1/8-mile.
Dean Marinis: Like Bruder, Marinis has established himself as one of the top runners in X275 with his big block nitrous combination. Marinis has a number of high profile wins to his credit, and is one of a handful of racers in the class to run in the 4.50’s.
Although the Powerglide and Superglide-4 are functionally similar, they share little more than a common name. The Pro Mod version of the Powerglide has been designed and manufactured from the ground up using the latest materials and processes to enable the transmission to be lightweight, yet handle more than three-thousand horsepower. If you’re looking for a quality transmission that can handle almost anything you can throw at it, the ATI Superglide 4 might be the right transmission for you.