Unless you’ve been calling the underside of a rock home for the last handful of years, then the automatic transmission and torque converter revolution taking place in the sport isn’t exactly earth-shattering news to you. With an industry-wide push in the advancement of torque converter technology in extreme racing applications, the automatic combo is presenting an epic challenge to the almighty clutch. And in a growing number of cases, the converter army has the clutch cars retreating from their stronghold.


The battle for supremacy against the clutch-equipped cars isn’t the only front the torque converter is fighting on however, as an internal struggle between two differing approaches to converter design and methodologies for planting the power to the ground have ensued. On one side, you’ve got the traditional converter design that operates on the basis of slippage, and on the other, the the lockup converter that’s clawed its way back into the fight.

Over the last two years, lockup torque converters have become a rather popular conversation piece in the context of high horsepower racing vehicles, thanks in due part to record-setting performances and an NMCA Pro Street championship, leading some to the belief that such an approach is the just the latest magic trick of the week that the industry has pulled out of its hat. That, however, couldn’t be any further from the truth.

To learn more about the past, present, and future of lockup torque converter technology, we’ve sough out some of the top manufacturers in the industry who at differing times have put their own revolutionary touch on the age-old converter.

The Companies We Talked To

Pennsylvania-based Transmission Specialties was one of the earliest manufacturers of lockup converters for high-end drag racing purposes, and continues operation today with more than 30 years of renowned experience in the market.

ATI Performance Products, which is virtually synonymous with the sport of drag racing, is well known for its line of Superglide transmissions and unparalleled quality, and has largely spearheaded the recent resurgence of the lockup converter.

Hughes Performance meanwhile, which opened its doors in 1971, is regarded as one of the top transmission and converter manufacturers in the drag racing market, with innovative products for race cars ranging from Super Street to Pro Modified. Hughes is the latest company to throw their hat in the extreme performance lockup ring with their new XP5 unit.

TCI Automotive, perhaps the most familiar name in the driveline marketplace, has been supplying automotive enthusiasts and racers with transmissions and converters for some 40 years, and today offers a complete line of lockup torque converters for many of the popular street and strip combinations.

A History Lesson In Lockup Converters

The traditional torque converter, as many of our readers are acutely aware, is a fluid coupling device that’s used to transfer rotational forces from a power source, in this case an internal combustion engine, to a rotating driven load. The torque converter acts like a mechanical clutch, allowing the load to be separated from the power source. This “donut” converts fluid pressure to lock the converter output shaft, thus transferring the engines power and torque to the driveshaft. Through what’s known as torque multiplication, the difference between the input and output rotational speeds provides what is essentially a reduction gear. Traditional racing converters however, exhibit some level of slippage at all times.

Transmission Specialties first developed their Pro-Line 6000 Powerglide transmission and converter system in 1998 and offered it through 2004 when some prominent organizations banned the use of lockups.

A lockup converter, just as the name implies, takes the traditional approach a step further and eliminates this horsepower-robbing slippage by completely locking the forces of the flywheel to the output shaft. In essence, it’s a 1:1 mating. Such a method has been used for decades in street vehicles, but it’s believed to have first been instituted for hardcore racing purposes back in 1975, when Steve Griner and Dave Coan partnered to build the first lockup racing converter.

These first iterations, which were mated to TH400 transmissions, locked up in first gear and at the time were said to be worth some three tenths and three miles per hour on average. API Racing Transmissions and Transmission Specialties later built their own versions.

With the records to prove it, the early lockup converters and automatic transmissions worked very well, but they were also plagued by issues that proved to be their downfall. Broken input shafts and leakage were a regular occurrence, but when they held together, they actually worked so well that some sanctioning bodies banned their use.

Transmission Specialties first developed their lockup unit in 1998, known as the Pro-Line 6000, which consisted of the transmission, converter, motor plates, adapter plates, air cylinder, and the works. At the time, racers the likes of Steve Kirk and Bob Rieger had these units in their race cars.

“They worked really, really well,” exclaimed Ken Kelley of Transmission Specialties. “Bob had one in his Firebird and was going 200 miles per hour back in 1998, which was just unbelievable at the time.”

Continued Kelley, “The problem back then was we were breaking input shafts and twisting the splines trying to get them to lock up, so that was their real downfall.”

A poster showing an exploded view of the Transmission Specialties Pro-Line 6000 lockup torque converter, displaying the extra clutch packs contained inside, on the wall at their facility in Pennsylvania.

When the venues banned the use of the lockup converters, Transmission Specialties and other manufacturers who had or were planning to develop one scrapped their plans prior to or around 2004 and put their focus back on the traditional converter line. API meanwhile, has continued to produce their lockup unit over the years and still does to this day.

But in recent years, the lockup converter has seen a resurgence in the racing world, namely in Pro Modified, Pro Street, and similar high-powered machines. In 2009, ATI Performance quietly outfitted Chris Rini’s Pro Street Dodge Stratus with a then-secret piece and set the class abuzz with unexplainable elapsed times and speeds. It didn’t take long for the cat to get out of the bag, and it was on from there.

Hughes Performance has just come to market with a version of their own, known as the XP5, that also aims at the mega horsepower realm.

“This was a project that we actually started working on in the first part of last year, and we really think that this is the next evolution of automatic Powerglide transmissions in drag racing applications,” explains Hughes’ Pete Nichols.

Lockups 101

So how does a lockup converter work exactly?

To understand how a lockup works, one first needs to understand how a torque converter functions. For the sake of avoiding web redundancy, click over to How Stuff Works and check out their great resource to get yourself up to speed.

ATI's SuperGlide 4 Powerglide transmission, designed for use in high-horsepower drag racing and other motorsports applications.

“The idea behind the lockup is that you get the torque multiplying advantages of a torque converter at the starting line and the efficiency of a clutch on the top end. In theory, a car that previously had a clutch should run the first half of the track quicker because it has more torque available at the starting line, and then it retains the clutches’ efficiency from there on,” says Nichols.

A lockup torque converter sports an extra set of clutches that are situated on the backside – or cover side – of the converter, of which pressure is diverted to from the transmission through a small cavity in the input shaft at a specified point. This pressure exerts movement on an internal piston that in turn locks the clutches together, creating a locked coupling between the turbine, cover, and input shaft. At this point, the converter is locked up much in the same sense as a clutch. In essence, it’s a hydraulic system.

Tested in 2009 and taking NMCA's Pro Street category by storm in 2010, ATI's new Outlaw Lockup torque converter has led the reemergence of the lockup in heads-up drag racing.

“The struggle with this functionality is producing the necessary pressure all the way through the input shaft,” explains ATI’s JC Beattie. “You”ve got a lot of horsepower and you’re drilling holes in the shaft, you have a significant amount of heat, O-rings that need to live, and of course everything has to remain straight. It’s certainly a big challenge when you’ve got a car that’s going zero to 230 miles per hour in six seconds.”

While different on the inside, lockup combos are much the same on the outside. The Hughes unit for example, starts life as a conventional Powerglide transmission case but is one inch longer overall to accommodate the one inch taller converter that packs the additional clutches. The transmissions feature a unique input shaft, a different front pump, and valve body.

Hughes Performance is the most recent manufacturer to join the lockup fraternity with their new XP5 system. This brand new combo is based upon an original Powerglide transmission, albeit measuring one-inch longer then standard and featuring a larger input shaft and an improved front pump and valve body.

Explained Nichols, “We just took a conventional Powerglide design and added the lockup circuitry to it. The shaft is physically larger in diameter at 1-1/4″ and is made of a special steel alloy, so the shaft itself is much stronger than a conventional Powerglide shaft.”

That increased shaft diameter and strength, a culprit of the early lockup combos, has made handling upwards of 4,000 horsepower without issue.

As one might expect when an engine shifts from slip to complete lockup, the engine RPM, even in powerful big blocks, is dragged down to a point that even the most out-of-tune set of ears can pick up on. At the time of Rini’s testing, some believed this audible tone to be a three-speed transmission, but that wasn’t the case.

“You’re not changing any gear ratios or anything like that; it’s still just a two-speed transmission,” states Beattie. “But the slip that you would have in a loose converter is eliminated. It does change the RPM, but you’re not mechanically changing a gear.”

Hughes Performance's new XP5 lockup torque converter, available in 9.5 and 10-inch designs, is activated by a 12V solenoid contained within the transmission.

The point of lockup differs as greatly as the combinations that do or could potentially use one, and its operation is controlled via an electronic solenoid or a timer that comes off of the transmission valve body and uses line pressure to hold the lockup clutches inside the converter. This solenoid can be activated with a button or switch mounted in easy reach inside the cockpit, and thus one can actually alter the lockup point to cope with tirespin or tireshake just as a clutch racer would alter their gear changes.

The Lockup Makes a Comeback

At the ADRL season opener in Houston in March, Texan Doug Reisterer put the lockup on fine display, piloting his ’68 Camaro to a 3.84 at 191 that was good for third in the Pro Nitrous qualifying order. His monster cubic-inch nitrous bullet was backed by ATI’s Outlaw lockup.

Rini, meanwhile, holds the current Pro Street national record at a stout 6.03 seconds at 234.86 miles per hour with his similar ATI combination. Chris also held the record in 2010 at 6.157 and 233.20. Along with the quarter mile performance, his brand spankin’ new ’69 Camaro has recorded a 3.91 to the eighth mile this season.

NMCA Super Street newcomer Jesse Violante has been testing ATI's new Outlaw Lockup torque converter in his nitrous-assisted '69 Camaro this season.

“The lockup program has been unbelievable,” says Rini. “We can run killer front half numbers and put up big mile an hour, so we kind of get both ends of the racetrack. We lock that thing up like a clutch car and run 235 with a Powerglide with a nitrous motor. And that’s big, because nitrous motors only have so much steam at the finish line.”

Whether running the eighth or quarter mile, Rini has found the lockup to his liking and believes it to be superior for his combination even in the shorter distance where lockup is never achieved. And with over 100 runs on the very same converter without fail or major servicing, it goes to show that the early lockup issues are a thing of the past.

“Right now, the only thing I have in my trailer is lockups. Sure they carry a little more weight, but it hasn’t hurt the ET at all,” said Chris.

Also in NMCA competition, Super Street newcomer Jesse Violante is running an ATI lockup in his new ’69 Camaro, and Tony Nesbitt is said to have his eyes on one, as well.

PSCA Pro Street racer Kelly Bluebaugh recently became the first racer to put the new Hughes Performance XP5 lockup through it's paces aboard his nitrous-fed Chevy Monte Carlo. After making the switch from a clutch, the WFO team has had to rework their entire combination, but they, along with Hughes Performance, expect a significant improvement in performance in the near future. Image credit:

PSCA and WCHRA Pro Street racer Kelly Bluebaugh is the first racer to get the Hughes XP5 on the racetrack aboard his nitrous-fed Monte Carlo, running a 6.56 on it’s maiden outing this spring.

“Kelly’s car was originally equipped with a Lenco and a clutch, and his nitrous and suspension tuneups were all set up for that. So he’s having to re-tune the entire car for the automatic. But once he gets it all sorted out, we’re expecting 6.20′s out of it pretty quickly,” says Nichols.

Bluebaugh is having a controller made that fully automates the lockup function based on RPM, allowing the lockup point to be set at any point on the track. With that, he’ll be experimenting along with Hughes locking the converter in low gear and/or earlier distances on the racetrack.

In addition to Bluebaugh, Hughes also has four other XP5′s slated to hit the track soon, including two X275 cars, a Top Dragster, and a West Coast Nostalgia Funny Car.

Turbocharged cars, because of their spooling needs, necessitate a loose stator and blade angle to accomplish this and keep the car from blowing the tires off. But like a freight train, once the boost and power management come in, they go from slip-needy on the bottom end to pouring every last coal to it on the back half. The result with traditional converters has been broke transmissions and ballooned converters.

NMCA Pro Street competitor Jeff Lutz has been dialing his combination in using a standard ATI torque converter and once there, will make the switch to an Outlaw Lockup combo to put some even better numbers on the boards.

ATI has been working closely with NMCA Pro Street competitor Jeff Lutz on his turbocharged ’98 Monte Carlo to fine tune the lockup setup, albeit with an initial step that doesn’t involve a lockup.

Explains Beattie, “The best way to get his car dialed in is to get the converter sorted out without the lockup, and once we get there, we can put the lockup in there and get the rest of the ET and mile per hour.”

NHRA: No Home For The Lockup

In the early 2000′s, the NHRA banned the use of lockup torque converters in a move considered to be as much about safety as it was the performance advantage. And to this day, the ban remains in effect in all classes, including Pro Modified, the Top Alcohol categories, Top Dragster, and Top Sportsman.

Because the quarter mile is where a lockup converter truly shines, the NHRA venue is where ATI, Hughes, and others believe they could best display their technology, and they say the decision is unfounded and ultimately detrimental.

Reigning NMCA Pro Street champion Chris Rini has been a leading proponent of the allowance of lockup torque converters in NHRA Pro Modified, where he feels they offer no advantage over a clutch-equipped car.

When asked if he would run Pro Modified if the lockup were allowed, Rini replied with an emphatic “yes.”

“I don’t even understand why they have the ban. I think it’s just because they don’t understand it. A clutch car is locked up at the finish line, so why isn’t a lockup allowed? They’re doing the same thing. I’ve made some phone calls to the NHRA about it and I can’t get a straight answer out of anybody. I’d go there in a heartbeat if we could get that rule changed.”

Rini believes the lockup converter gives automatic transmission-equipped Pro Modifieds a better chance to compete, and with the struggling car counts seen this season, might entice more racers to show up. As well, because an automatic car goes down the racetrack nearly every pass, it only adds to the entertainment value.

“They need to modernize and get with the times,” Rini says. “When you talk to them, they reference things that happened a decade ago, but times have changed.”

Not Just For The Extreme

Lockup torque converters may be making a resurgence in the high-end drag racing world of late, but they certainly aren’t limited to this segment of the arena. Several manufacturers, including the folks at TCI Automotive, have developed and offer lockup converters of several size variations for GM, Ford, Chrysler, and AMC drag racing applications more suited to bracket-style racing.

“At one time, a lot of people with higher horsepower, 550 to 600 horsepower applications wanted a non-lockup because the converter clutches wouldn’t hold to be locked up and raced with,” explains TCI’s Scott Miller. “Now, the technology in clutch material and converter and transmission design is vastly improved. You can run a 4,000 or 4,500 stall converter and it still be a lockup, and the clutch will hold up.”

An exploded view showing the internals of one of TCI's Lockup Drag Racing torque converters. Images courtesy

Like their several thousand horsepower brethren, these such converters function in the very same manner and provide the same benefits from their zero slippage operation, such as improved elapsed time and almost certain trap speed gains.

“The 1:1 ratio really helps out on your top end mile per hour and a car will just run a lot better that way,” says Miller. “And there’s also less heat, of course.”

For converters built for such purposes, one area in which they differ from the extreme applications we’ve spoken of previously is in the engaging process. The method differs depending on the transmission the converter is mated to, and in some cases the functionality is much like a Pro Modified car with a toggle switch, while others are done without driver interaction.

TCI produces a full line up lockup drag racing torque converters of the 9, 10, and 11-inch variety for GM, Ford, Chrysler, and AMC applications.

“On the older 700R4′s, you would just have an on/off switch wired into the transmission, and when it goes into whichever gear you want it to lockup in, you’d flip that switch on. The other option for later model electronic transmissions, like the 4L60E or 4L80E, it’s all controlled by a computer. It would all be programmed using a tuner or a standalone transmission controller,” explains Miller.

While aimed at engines producing in the neighborhood of 400 too 600 horsepower like that of a street car, Miller explains that these are primarily designed for racing use.

“The only time anyone would really want to use one of these on the street would be for grudge racing or just playing around. It’s not something that you’d want to drive every day.”

Lockup converters are but one of a handful of approaches to torque converter functionality, and while none is deemed superior in all applications and situations, manufacturers like ATI and Hughes believe there are some distinct advantages to the lockup, and they’re firmly behind the belief that the lockup converter is the way of the future. And while the war between not only the staunch supporters of the automatics and the clutch but amongst the bright minds in the automatic transmission and converter world is sure to wage on for some time, it’s evident that the lockup is back and it’s not going away quietly this time.