TORQUE CONVERTER UPGRADE
Beefing up your diesel pickup’s factory torque converter with a heavy-duty billet-style improves power, fuel economy and transmission durability — you can bank on it
By Larry Walton, Editorial Services West
When it comes to towing, the weight of the trailer and torque being generated by that diesel under the hood are the very factors that wreak the most havoc on a heavy-duty pickup’s transmission. More specifically, towing puts a tremndous strain on the torque converter as it transfers power from the engine to the transmission.
In general, manufacturers did not design the stock torque converters to withstand the types of abuse those of us with hot-rodded diesels and huge trailers heap upon them—especially when the engine has had the performance modifications that allow today’s diesels to optimize their torque and horsepower potential.
A torque converter’s job is to provide a fluid coupling that allows the engine to continue running when the vehicle is stopped in gear. Because the inverter and turbine that push and receive the fluid can never achieve a solid lockup, most torque converters also have clutches that engage to achieve a mechanical connection between the engine and the transmission.
Lower quality clutch compounds in stock converters work fine when the engine is stock or loads are light. But add more horsepower, more torque and/or a heavy load and clutches start slipping under the extra strain.
This slipping causes friction between the clutches, which, in turn, produces a tremendous amount of heat the stock converter cover is ill equipped to handled.
According to John Domaschofsky of Dan Judy Automotive (501-362-5830), “when the clutches start burning there’s so much heat generated it turns the outside of the torque converter bright blue.”
The heat also causes the torque converter housings to deform or balloon. This ballooning causes looser tolerances, which, in turn, create higher stall speeds that produce even more heat. A deformed torque converter housing also reduces the clutch surface area causing more slip, more heat and more debris.
“Debris in the transmission fluid is from the heat damaging the seals and plastic pieces in the transmission.,” says Domaschofsky, who has spent a lot of years repairing automatic transmissions and replacing torque converters.
Heat also causes fluids to degrade.
“The transmission and the torque converter share fluid,” elaborates Domaschofsky . “When the torque converter starts to fail it will produce material that will contaminate the transmission. The fluid comes out of the torque converter and into the cooling system.
“As the torque converter and transmission begin their downward death spiral, material can get caught and plug the cooling system. This, of course, causes even more heat build up.”
Fluid that is returning to the transmission from the cooling system gets dumped onto the planetary gears.
“Any material that happens to be in the fluid goes directly onto the gear surfaces. This is why it’s not a good idea to keep running a damaged or inadequate torque converter. In all the years I’ve been in the business, I’ve never seen a torque converter failure that has not caused damage to the transmission,” says Domaschofsky.
So, it’s fitting that Gale Banks Engineering, which is responsible for their share of the aftermarket diesel power out there on the road, develop a special high-performance billet torque converter that can handle the new-found power.
We tested Banks Billet Torque Converter (part #72521; $995 plus $250 core charge) in our F-250 Super Duty with a 7.3 liter Power Stroke, which has reaped the benefit of electronic and exhaust upgrades to really boost its power.
Along with the new torque converter, we installed a Banks TransCommand unit to beef up clutch line pressures.
The portion of the stock torque converter that is bolted to the engine flexplate is a stamped steel housing with welded-on tabs, which can deflect or distort the housing under sustained high loads. This distortion usually causes high spots on the machined metal surface that is engaged by the lockup clutch. With less metal surface contacting the clutch surface, clutch slippage, dust and heat multiply in a vicious cycle.
This billet construction reduces flex thereby retaining clutch contact surface even under heavy loads. This means quicker, surer lock-up and less slippage, which, in turn, helps prevent heat, wear and fluid contamination.
Other features of the Banks converter that make it tougher also improve performance.
For example, stock inverter and turbine blades are held in place by small tabs that protrude through a slot. The tabs are bent over to hold them in place. These fins can become loose and diminish in efficiency when subjected to high loads.
The fins in a Banks torque converter are furnace-brazed in place to prevent loosening caused by high power and weight loads. Furnace brazing creates a much stronger bond to withstand the rigors of heat and fluid pressure.
The Banks dual-disc clutch maximizes surface area to reduce slippage under the combination of high torque and heavy load.
Carbon-ceramic clutch materials, which improve on the stock cellulose-based paper material and means less clutch material is being ground off of the plates and into the automatic transmission fluid.
We started our project by installing a transmission oil temperature gauge because fluid temperatures are one of the best indicators of what is going on with the torque converter. In fact, an transmission oil temperature gauge is a good idea for anyone who pulls heavy loads and/or has significantly increased the power output of their tow vehicle.
We installed the sensor for the temperature gauge in the line near where the fluid leaves the transmission before going to the cooler. This location gives a better read on torque converter activity instead of just how well your transmission cooler is working.
We monitored transmission temperatures under several conditions including town driving, highway cruising and acceleration runs. As expected, trans temps went up when each torque converter was working the hardest in stop and go traffic and under heavy acceleration.
Torque converters are happiest when locked-up and cruising. In fact, the experts we talked to said the hottest conditions for your torque converter are when you are at low speeds with a load – like backing up into a camping spot or pulling a steep incline from a stop – any conditions where a manual transmission would need to slip the clutch to get going or change gears.
Our tests showed slightly lower transmission temperatures with the Banks set-up. On average, the temperatures were 5 degrees lower under a variety of conditions with the Banks equipment installed.
We ran a series of tests while towing a 7,000 pound trailer first with the stock torque converter then with the Banks TransCommand and billet torque converter installed.
FUEL ECONOMY FINDINGS
Our initial fuel economy tests saw no measurable changes between the OEM set-up and the Banks upgrade. This is not surprising because we towed the 7,000 pound trailer at a highway cruising speed of 65mph.
Both the stock and the Banks torque converters would have been in lock-up mode in these conditions, which means the clutches were producing a good non-slip connection between the engine and the transmission.
Subsequent testing over a six-month period of combined city/highway/work/recreation driving conditions showed our test truck gained about 1.5mpg.
This is what we expected to see in fuel economy improvements in stop and go conditions with the Banks converter because with a lower stall speed and quicker shifts it should take less fuel to get things moving.
The same holds true under a heavier load because slippage in the torque converter is reduced with the Banks upgrade. — LW
ACCELERATION WITH ATTITUDE
Our muscled-up F-250, towing the trailer in combination with the stock torque converter averaged 0-60 MPH acceleration of 15.4 seconds. During the acceleration tests we noticed a considerable amount of shudder, which we attributed to slippage in the torque converter clutches.
With the new Banks torque converter installed, the average 0-60 MPH acceleration time was 14.7 – a ½- second improvement.
Acceleration times would have been even faster if it wasn’t for a new issue: wheel spin.
The new torque converter does its job of transferring engine torque to the driveshat so effciently there was a significant increase in wheel spin even with the heavy trailer tongue weight.
That shows how much more power the billet converter is putting to the rear wheels compared to the stock unit.
During our acceleration tests we also recorded 40 – 60mph times. The average 40-60 MPH time with the stock torque converter was 8.5 seconds. The average 40-60 MPH time with the Banks Billet Torque Converter and TransCommand combination was 7.6 seconds.
This represents an improvement of nearly a full second during those on-ramp spurts, and shows the true value of doing such an upgrade.
We found that the lower stall speed of the new torque converter was noticeable in normal driving conditions. Or, in layman’s terms, it takes less throttle input to get things moving. We also noticed the F-250 shifts quicker and firmer under hard acceleration.
Because the new converter was installed to improve durability and protect the transmission, we were pleasantly surprised by the improvement in acceleration and driving fun. Any improvements in fuel economy will likely be negated by the urge to stand on the throttle more often.
Upgrading to the new Banks Billet Torque Converter could be installed by a skilled backyard mechanic in about a day. The manual that comes with it is very detailed, but the recommended tools list has some specialized items like transmission hoists, flywheel rotating tool and a torque converter holding tool.
If you take an F-250 like ours to a good transmission shop, the installation costs will probably run from $370 – $530 depending on your location. Shop installation of the TransCommand costs about $75. That brings the whole job, with parts and labor, in at about $1,725.
That may sound like a lot of money for a fancy torque converter. But keep this in mind: Parts and labor to replace a stock torque converter ranges from $800 to $1,000 – and if you wait for the original to go out the transmission will probably need some work as well. The cost for rebuilding a Ford F-250 4R100 automatic these days ranges between $2,800 and $3,500.
Taking that into consideration, we think the Banks Billet Torque Converter and TransCommand are wise investments for those who are hauling heavy loads and/or have increased the power of their trucks with performance upgrades.
Gale Banks Engineering highly recommends installing their TransCommand (part #62570; $ 277) transmission command module along with the Banks Billet Torque Converter.
The truck computer monitors throttle position and rate of acceleration to determine load, and then increases or decreases line pressure in the 4R100 automatic.
This computer interface produces a smoother shift under light load and firmer shifts under heavy load to prevent clutch slippage.
Banks developed the TransCommand to compliment their other performance parts because with more power the truck will accelerate with less throttle making the computer think it’s time for smooth shifts when the increased power actually calls for firmer shifts.
So the TransCommand senses load conditions to accelerate line pressure ramp rates. This provides firmer shifts under higher power and bigger load conditions.
While the stock line pressures offer a smooth and comfortable shift, a firmer shift is often necessary when towing or when performance modifications have increased engine power.
These conditions produce increased clutch slippage that can cause heat degrading of fluid and can deposit particles that damage the transmission.
In addition to extending torque converter and transmission life, the TransCommand increases performance by reducing or eliminating slippage in the torque converter.
Instead of wasting energy in internal friction, it supplies more consistent power to the wheels.-LDW
While You’re There
While the truck is on the rack and the drivelines are disconnected, it’s a good idea to check the conditions of the u-joints, drivelines and seals.
U-joints can be tested while hooked up to see if they are solid, but they need to tested while disconnected to see that there are no catches or stiff spots.
During our inspections we found some worn teeth on the ring gear that is engaged by the starter.
So Dan Judy replaced the ring gear along with the flexplate while these parts were accessible during the torque converter install.
This replacement costs about $25 in additional labor while you’re already there compared to over $400 if you had to go back in and do it as a separate repair.-LDW
Contact: Gale Banks Engineering, (800) 695-1435, www.bankspower.com