We think transmissions don’t get the proper credit they deserve. While everybody wants to talk about how many cubic inches, carburetors or how much horsepower your ride’s engine cranks out, very few people bother to ask, “What stall converter you running?” or “How many discs does that clutch have?” Nope; like the Jan Brady of powertrain parts, the transmission will always – and unfairly – live in the shadow of its sexier sibling.
Since Oldsmobile introduced the Hydra-Matic in 1938, the first American-made clutchless hydraulically-operated transmission (a factory option available for a whopping $57!), Americans have been warming up to the automatic transmission faster than anywhere else in the world. Designed to meet the growing demand from both the daily commuting set and those horsepower-hungry types, the first TorqueFlite came into existence in 1962.
Built to Last
Surprisingly enough, the sturdy 727 TorqueFlite design survived through the early years of unmerciful “neutral-drop” launches from those racing push-button shifted Chryslers. While such treatment casually murdered one TorqueFlite after another, word quickly spread that the new Mopar slushbox was a force to be reckoned with. Designed to be nowhere near as complicated as GM’s TH350 and 400, and more streamlined than Ford’s C4, the 727 proved formidable behind the HEMI or Mopar’s high-revving LA-block.
But, as it is with most automatics, not all TorqueFlites are the same. Since our project ’69 Dodge Charger Killer Kong was once a mild-mannered two-barrel 383 B-Block-powered daily driver and not a snarling factory-equipped 426 HEMI-powered street bruiser, the included 727 3-speed came woefully ill-equipped to handle the power of a Magnum 440 or a 7-liter elephant – not to mention the 750-horse naturally-aspirated hemispherical-headed monster we’ve got cooking.
Differences between the degrees of performance are various, but usually add up to a discrepancy in the total number of front clutch plates, clutch springs and their respective spring tension, governor weights, the pre-programmed up-shift speed, band friction material and construction, as well as the torque converter stall speed. All of these variants can have a significant impact on the given TorqueFlite’s behavior.
Our particular 727 was in poor shape. Needing as much help as we could muster, we first called Tod Struck at Inline Performance Specialist for some advice. Struck’s been piecing together race and street/strip TorqueFlites for nearly a quarter-century now and knows his way around a Mopar gearbox.
He suggested, “Knowing the kind of power you’re wanting to make, and being that [the '69 Charger] is such a big car, you’re going to want to take extra precautions.”
The plan was simple: less moving parts meant less potential for breakage. We wanted a reverse-manual valve body and a high enough stall converter to spin those tall 4.56 gears to get our big B-Body on its way. Where we came short was the guts. Where should we start?
“A bolt-in sprag, for one,” Struck continued. While impressively strong, the 727 does have an Achilles’s Heel, an overrunning clutch assembly, or “sprag.”
Designed to prevent excessive or potentially catastrophic damage if the transmission is allowed to free-wheel, the transmission’s sprag is a pressed-in housing containing spring-loaded rollers to help slow (and stabilize) the transmission’s rotating assembly.
And since all of the combined kinetic energy of the transmission and engine are absorbed by the sprag, it can – when coming loose – actually start to spin out of the transmission case with destructive effect. To counter this, many racers resort to drilling and tapping the factory sprag, bolting it down in place. Luckily, there’s an easier – and cheaper – way to fix this, thanks to TCI Automotive.
TCI is no stranger to top-of-the-line transmission performance. Since 1968, TCI has earned itself a solid reputation for quality products, whether you’re looking to simply rebuild your transmission or eke out as much bulletproof performance as you can. As for our needs, TCI designed an overrunning clutch kit (i.e. bolt-in sprag) that’s already drilled and tapped, as well as fitted with new springs and rollers.
Since our TorqueFlite needed much more than just TCI’s new sprag kit, we consulted with TCI’s Scott Miller. “A full manual reverse shift-pattern valve body should be no problem on the street,” Miller explained. “But to keep [the 727] together, you’ll need more than just the valve body. You’re looking at our Super Street Fighter kit.”
Ready For a (Street) Fight
Since our factory 727 came pretty weak – compared to those TorqueFlites equipped with HEMI-grade components – we counted on a full rebuild of the TorqueFlite. TCI has several levels of performance kits, namely the Sizzler, Street Fighter, Super Street Fighter, and Race transmissions. Officially, the Super StreetFighter is designed to bridge the gap between their StreetFighter and Race series transmissions, for cars producing up to 600 horsepower. Knowing we’d be well north of the 600HP mark, we consulted Miller again.
“Don’t worry. Most of the [components] used in the Super Street Fighter are used in the full Competition Series transmissions as well,” explained Miller. “We’ll use Red Eagle clutches, heat-treated Kolene steels, a Red Eagle flex-style high performance intermediate band, Kevlar high performance bands, a two-extra-quart capacity deep aluminum pan, and a 4.2 ratio band apply lever.”
For those do-it-yourself trans builders wanting to reduce their TorqueFlite’s slippage, Inline’s Tod Struck also suggested, “A lot of guys use all reverse clutches. They’re thinner than the forward clutches, which allows you to pack more in. It’s an old trick.” While we weren’t going to be employing this tip, it was a helpful bit of advice.
Coming Through In a Clutch
Disassembling our transmission only took a short amount of time. Starting from the outside and working our way in, we removed the old torque converter, which we believe spun around 1200-1600RPM from the factory. Next came the cracked and broken rubber cross-member mount, speedometer gear drive, and shallow stamped steel pan. Our new TCI aluminum pan adds over 2 additional quarts of ATF and is finned for better cooling, a stark improvement over the dented steel one.
With the pan gone, we had direct access to the valve body. Normally referred to as the “brain” of the transmission, the valve body acts very much like your engine’s camshaft, with pre-programmed points and circuits mandating shift points and fluid pressures.
Since we’re going with a reverse-shift-pattern manual valve body, we no longer need to worry about slippage as we’ll be shifting our automatic manually from here on out.
Removing the valve body required the twist of ten bolts with the attached filter (held on by four screws), and, when gone, revealed the clutch drums and servos that truly make our transmission come to life. The oil pump assembly is held in by seven bolts.
Many find it difficult to pull out without the use of a thread-in slide hammer or having to press it forward from the inside. Either way, with the pump out, the planetary gears can be removed easily; held in by a snap-ring (or “circlip”) the planetaries, clutches and drums all slide out in sequence.
It’s a smart idea to double check your planetaries for any “slop” in your gears. Thankfully, our TorqueFlite’s planetary gears were in good shape and showed a safe amount of side-to-side “play.” Unfortunately, our clutch drums exhibited some surface rust. A couple passes of emery cloth or steel wool knocked off the oxidation without much ado. Otherwise, we’d have to turn the drums down on the lathe. Many shops, in fact, will mill a step into the drum to give the band a guide. Yet another little trick that some like to use.
Rebuilding Our TorqueFlite By The Numbers
- 727 Bolt-In Sprag Kit (PT# 127000) $77.02
- 727 Red-lined Flex Band (PT# 125500) $31.36
- 727 Forward/Direct Steel Plates 0.068″ (5 ea.) (PT# 124066) $38.65
- 727 5.0 ratio Hemi Band Apply Lever (PT# 146900) $31.56
- 727 Cast Aluminum Deep Pan (PT# 128000) $160.10
- 727 Reverse Kevlar®-lined Band (PT# 125505) $17.14
- 727 Forward Clutch .061″ (PT# 124500) $28.52
- 727 Racing Overhaul Kit (PT# 128600) $62.38
- 727 StreetFighter Torque Converter (PT# 142203) $539.91
- 727 Direct Aluminum Drum (PT# 123900) $711.23
Getting Our Act Together
Putting the TorqueFlite back together was merely a reversal of the disassembly process, only doing so a bit more carefully and using fresh, new components. With with the tail off, TCI thoroughly cleaned the bare housing, blowing out the circuits before reassembly. TCI was mindful to apply a dab of grease to each hard contact point. While the TorqueFlite will be running TCI’s Max Shift ATF, the added precaution ensures a safe installation and additional insurance from unneeded wear.
The rear gear train went on quickly after installing the bolt-in sprag. The rear drum friction band goes in first, mating up to the rear band articulating arm. The arm is actuated via a sprung servo (which we replaced with a billet piece), and constricts the band when shifted either in low (first gear) or reverse. The clutch drum slides in next, which indexes into the bolt-in sprag. The sprag allows the drum to spin clockwise, but locks it from turning counter-clockwise.
With the drum in, the output shaft can go in next. The rear annulus and three-pinion planetary go into the drum afterwards. Many top performance builders prefer that the three-pinion planetaries be swapped out with four-pinion billet pieces. While our front planetary was a four-pinion, we kept our costs low by retaining our rear planetary. We’ll make sure to keep the down shifting (or engine braking) to a minimum.
The forward drum (fitted with the two sun gears) was next followed by the the front annulus and aforementioned four-pinion planetary. Capped off with a single snap ring over the end of the output shaft, the whole assembly is held in place.
Joining the output to the input shaft is the forward gear assembly. The front and rear clutch drums were repacked with new springs, retainers and seals before the Red Eagle clutches and new high performance steels could be shuffled in. One after the other, the rear and front clutches index together on the input shaft before the pump goes on. But before the pump can be installed, the forward band is inserted.
Once sealed up, TCI rolled the 727 over and adjusted the bands properly, torquing the adjustment screws to 72 ft. lbs. Its usually a good rule of thumb to adjust the screws once, over-tighten them a turn or two and back them off before readjusting the screws back to the proper torque rate. This is a good tip particularly as this will set the bands.
With much less hardware to worry about, the manual valve body requires much less effort to bolt down than a regular automatically-shifted valve body. Attached with a new filter, the bottom end of the 727 was all but ready. Before buttoning up the new deep pan, the transmission was pressure tested. This test ensures that the new servos actuate the band arms, while the transmission is systematically rolled through all the gears. It’s the last bit of double and triple-checking that goes into a TCI-built performance transmission.
Buttoned Up And Ready To Burn Some Tire
With the pan on with a fresh gasket, Kong’s newly-TCI-rebuilt 727 TorqueFlite was given a fresh coat of paint (as is the TCI custom) and shipped back home, accompanied with a new TCI Outlaw Shifter, a Super Street Fighter torque converter, and one of TCI’s Performance Transmission Cooler kits. We love the Mopar-appropriate pistol grip-design of the billet aluminum Outlaw shifter, and even toyed with the idea of maybe swapping out the black grip with a woodgrain replacement. Although the Outlaw can come with an electric shifter kit and one- and two-button triggers, we opted for the simplest setup with a Park/Neutral safety switch.
Transferring the power from the crank flange to the transmission is our new high-stall torque converter. Made with furnace-brazed fins, needle bearings, and a hardened, pre-ground hub, the Super Street Fighter converter is the right pick for our big block set up, particularly as we’re running 4.56′s with 30-inch tall tire. Pitched with a 3,800-to-4,000RPM stall, our 9-inch converter will flash pretty dang hard.
Totaling out our care package from TCI was their Performance Transmission Cooler kit. Constructed from aluminum and powder coated black with #6 AN fittings to work with high pressure lines, we’ll definitely put this to good use.
Building a hard-hitting engine is always the flashy, fun thing to talk about, but without the proper gearbox to back up all that power, your big and brash big block won’t have anywhere to go. We’re working on Killer Kong’s powertrain a little backwards on purpose because we want to emphasize how crucial the rest of the package is. While a stroked lightweight HEMI is a cool catch for this project car, it’s the collaborative effort of all the parts that make it a success, and with TCI’s help, we’ve got one less part to worry about.