Torque Converter Swap Nets Big Performance gains with Ford Mustang GT
In the scheme of performance improvements, engine modifications get all the glory. After all, when it comes to getting from point A to Point B quickly the most obvious solution is adding more power. But there is an often-overlooked improvement with automatic transmission-equipped vehicles, which quickly enhances performance with no loss of drivability. Best of all, it’s a true bolt-on part that can be installed in an afternoon. That simple change - a torque converter swap.
 Our test vehicle is an 2006 Mustang GT |
The subject of our swap is the hottest vehicle on the planet, the new Ford Mustang. Our test vehicle, a 2006 Mustang GT, was completely stock right down to the P235 tires and shiny black factory-applied paint. This untouched Mustang would be the perfect subject for our torque converter test and recipient of the latest in torque converter science as applied by the engineers at
TCI Automotive®. After a quick stop by the Memphis Motorsports Park for some base line performance figures (14.35 seconds at 97.05 mph in the quarter mile) we headed over the dyno at
COMP Cams® headquarters. Testing for rear wheel horsepower and torque the bone-stock ‘Stang netted 248 horsepower and 241 lb. ft. of torque. With the number locked down, we were ready to see just what was possible.
Why does it improve performance?
Torque converters are truly a mysterious component to most performance enthusiasts. Understanding just what they do can be challenging. We all know we need this component in our car or truck, but what exactly goes on inside that odd-looking part is unknown by many folks, both novice and accomplished racer alike. In a nutshell, the torque converter does exactly what they name implies and transmits engine power into torque that drives the transmission and ultimately your rear tires. Furthermore, it multiplies this engine torque providing required performance benefits to your transmission’s operation.
With the TCI® performance torque converter, the stall speed of the torque converter is changed through modification of the stator. In their top-of-the-line
Super StreetFighter® torque converter for the 05-06 Mustangs (note that a TCI®
Streetfighter® torque converter was installed in the stock Mustang – the
Super StreetFighter® into the racing Mustang – see second story below), the multiplication is further enhanced through the usage of a completely custom hand-built steel stator creating as much as a 2.5 to 1 torque increase. This moves the “flash” stall speed (the point at which the vehicle begins to first move under wide open throttle) to a higher rpm. In the case of our stock Mustang, the flash stall speed was approximately 2500 rpm. With the new
StreetFighter®, the new stall speed was nearly 3000rpm.
So how does this help performance? With the higher stall speed, three good things happen. First, the increased torque multiplication of the converter results in quicker 60 ft. acceleration times. Second, the engine rpm is higher at the start of the run placing it at a higher horsepower generating point within the engine’s power curve. Third, the engine rpm drop between gear changes is reduced, increasing the efficiency of the acceleration run.
The performance isn’t in the numbers.
With our new TCI®
StreetFighter® torque converter safely back in place, we again headed for the chassis dyno to see the fruits of our labor. The result – exactly the same power figures for both torque and power. A surprise? – not to TCI® Engineer Kevin Winstead.
“With a torque converter change such as this where the stall speed is raised, the rear wheel dyno power can actually be slightly reduced,” explained Winstead. “The performance benefit is in the performance feel and shift point selection.”
That fact was clearly realized by the owner of the vehicle Zach Tibbett who noted a “personality change" to the vehicle the instant he first stepped on the accelerator. Despite the higher stall speed, he felt the vehicle reacted more quickly to throttle input and faster even in cruise mode.
“There was an immediate difference in seat-of-the-pants performance,” stated, Zach. “The car is much quicker than previously. In comparison to the original converter, the car’s acceleration seemed greatly improved and the shifting felt crisper. The performance figures from the track further backed that up.”
How much faster was the Mustang after the torque converter change? How about 0.41 seconds, nearly a half second improvement in the quarter mile with no other adjustments. The best time for the black ‘Stang, 13.94 seconds at 96.45 mph. Noting that true engine horsepower to the rear wheels is denoted by the mph numbers, the fact that this was slightly down was in keeping with our calculations.
So what have we learned? There is hidden performance locked within the torque converter of late model Mustangs. The new Streetfighter line of torque converters can help you unleash that performance with a simple converter swap. Best of all, it serves as a great launch pad for other performance adder options knowing that the TCI®
StreetFighter® torque converter is up to the task with improved internal quality way beyond the factory component. Better performance and durability – what more could you desire?
Follow along as we take a step-by-step look at how TCI® upgraded Zach's GT with a new
StreetFighter® Torque Converter...
Zack Tibbet’s 2006 Ford Mustang exhibited excellent performance right off the show room floor. In street trim using the all factory parts, the black GT turned at best time of 14.35 seconds at 97.05 mph.
Our first test was to check the stall speed of the torque converter. In a power braking stall speed check (holding down the brake and pressing on the throttle until the car moves) the figure was 2100rpm.
Using the COMP Cams® chassis dyno, the power numbers for the Mustang were checked. The results were very consistent at close to 250hp and 240 ft. lbs. of torque.
Step one was to unhook the battery cables. With computer-controlled systems, this is an important safety precaution.
The driveshaft is a complex component in new generation Mustangs. Unbolt it from the rear of the transmission and then the rear mounted hoop and move it out of the way to provide clearance and allow lowering of the transmission.
Note that a centering pin protrudes from the rear of the transmission and can hang up the driveshaft movement.
On the 05 and newer Mustangs equipped with the 5R55 transmission, it isn’t mandatory to drain the transmission oil. However you will need to refill the transmission once the new converter is installed because of the fluid lost during removal of the converter and the cooler lines. This transmission does not have a transmission fill tube so fluid must be pumped up into the transmission through this fitting to refill fill the pan.
Next unplug the oxygen sensors from the underside of the transmission body. These sensors simply plug into the main wiring harness.
After removing the inspection cover, remove the nuts that attach the flex plate to the torque converter mounting plate. Four nuts must be removed. The engine can be turned over with a remote starter switch but will require reconnecting the battery for this step. Remember to unhook it again once finished. The factory to keep them from backing off once they have been torqued in place uses special “pinch” nuts.
Using a 22mm wrench, carefully remove the sensors from the pipes. If you don’t, there is a possibility of damaging them or the attached wiring.
Unhook the transmission cooler lines making certain not to bend them or strip the line fittings. The cooler lines will leak fluid once you unhook them so be ready with a catch pan.
Unbolt the starter using a ¼-drive ratchet. The starter can be simply tucked out of the way to provide enough clearance to lower the transmission.
Using a long extension on the socket wrench, remove the bellhousing bolts. With a transmission jack carefully positioned under the transmission, unbolt the exhaust system at the catalytic converters and the rear crossmember. Slowly lower the transmission to provide enough clearance to reach the upper bellhousing bolts.
Be especially careful with the transmission linkage system unclipping the system and noting the original position of these parts.
Carefully pry the flex plate away from the back of the engine. The studs protruding from the torque converter mounting plate have a tendency to catch on the back of the engine.
The Ford Electronic automatic transmission has a number of connections to be found on the passenger side of the unit. Carefully unscrew the main connector from the housing and unclip the other sensor connections. Note the original sensor placement for easier reinstallation later.
You just can’t be gentle enough when working with these plastic connectors. Most of them feature a pinch and release connector, but some are far more complex. Take your time, as replacement connectors can be very expensive.
This is the most critical part of the torque converter swap. When lowering the transmission make certain it is carefully balanced (attaching it to the jack with straps is a good idea).
Clearing the transmission cooler lines can be a problem. Make certain they don’t become smashed or bent during the removal process.
The transmission, finally free from the car, is now ready to see removal of the torque converter. Keep your hands on the converter so that is can’t slip off and be damaged.
Be careful that the transmission is balanced properly on the jack and remember, when you remove the converter that you are removing a large amount of weight and the transmission can again become unbalanced.
The converter holds approximately 3.5 to 4 quarts of oil. When you remove it from the transmission, it will release some fluid so catch it with a drain pan. Once out of the vehicle, drain the converter in a catch pan.
Unbolt the torque converter mounting plate from the old converter in this manner.
The old torque converter mounting plate must be bolted to the new TCI® Streetfighter® torque converter. Use the same nuts used by the factory to reinstall the flex plate and torque them to factory specs.
Pre-filling the new torque converter with at least two quarts of factory recommened transmission fluid is an important step. Filling it completely will only cause it to leak out when you lift it back onto the transmission snout.
Lift the converter on to the snout and twist it until it seats on the input shaft (you’ll hear it go into position). There are three distinct engagements to be made by the torque converter. Note the final position of the converter. If your converter doesn’t seat firmly or is not in the position, work the converter back and forth until it does. This is critical to making the transmission operate properly.
The oxygen sensors must be reinstalled properly to make certain the vehicle electronics work correctly. Make certain that the coverings are in the right place and that the wiring is situated so it cannot come in contact with other parts or catch on road hazards.
Without question, this is the most frustrating pan fill system we’ve ever encountered. Without a fill tube, pumping oil up through the center of the oil drain plug must fill this transmission. The inner tube in the drain plug sets the fluid level. Once the oil in the pan has reached the correct level, the fluid will drain back out of the center tube. In order to properly fill the car, it must be idling in park and be level. Make certain that the main drain plug is snugged up, fill the system and then reinsert the center Torx-headed plug.
The test came during a test and tune session at Memphis Motorsports Park. The best time for four runs: 13.94 seconds at 96.45 mph – nearly a half second quarter mile improvement.
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