Frequently Asked Questions
I read that some company's recommend that I use a non-locking converter, What is your thoughts on this matter?
We are aware of Company's that are recommending people use non-locking (dummy) style torque converters. This just doesn't make any sense to us for the following reasons:
First: When a modern torque converter is in its engaged (locked up) or mechanically coupled state, it creates a direct mechanical connection between the engine and the input shaft of the transmission! The connection thats created during lock up is almost identical to the mechanical connection that occurs whenever the driver lets out the clutch pedal in a standard transmission vehicle and creates a very efficient means of transmitting torque from the engine to the transmission! The U.S. government has stated in many reports that this feature has been responsible for a major improvement in fuel economy. This has been well documented and really isn't debatable.
When the converter is in an unlocked (disengaged) state,
there is going to be some loss (slip) across the converter
during almost all driving situations because of converter
slip. The results of this loss or slip is work heat generated
into the transmission fluid. How much heat depends on how
much loss (slip) is occurring during a specific driving
situation. Some of the factors that effect the amount of
heat generated, include towing, driving speed, climbing
steep mountains or hills, wind effect and weight being carried
etc. Overheating is the number on cause of failure in automatic
transmissions so controlling this heat is very critical
to longevity. As long as the cooling lines are routed to
the vehicles radiator, no heat generated inside the torque
converter while driving is always better than some heat!
Dummy or non locking converters never lock up and are therefore
a constant source of heat than must be effectively dealt
Just like pedeling a ten speed bike, this higher the gear
ratio your in, the greater the torque that must be supplied
to maintain a result. Transmissions by the very design are
meant as multipliers of engine torque, for example, while
in 3.06:1 low gear, 100 lbs/feet of torque applied to the
input shaft will result in 306 lbs/feet leaving the output
shaft! Second gear, the same 100 lbs/feet of torque applied,
results in only 163 lbs/feet of torque at the output shaft.
Third is 1:1 so the same 100 lbs/feet of torque leaves at
100 lbs out! Overdrive gearing results in a torque loss
across the transmission since 100 lbs/feet in results in
only 70 lbs/feet out! This means to achieve the same results
while in overdrive, the engine must supply 30% more torque
to the input shaft! This results in working the fluid inside
the torque converter 30% harder any time the transmission
is in overdrive! The result of the added work is heat. High
stall converters make this phenomonom even more severe.
Locking (engaging) the converter clutch eliminates
OBSERVATIONS AND RECOMMENDATIONS
If you are going to use a high stall converter, tow, haul heavy loads, have a lifted vehicle with big tires, etc, we strongly recommend installing a temperature gauge to monitor the fluid temperature inside the transmissions pan. The fluid in the pan is primarily fluid that has just returned to the transmission after passing through the heat exchanger located inside the vehicles radiator. Locating the temperature gauge sender in the transmissions pan will tell you whether your vehicles temperature control system can handle the temperature management properly. We have installed and monitored all vehicles that have been through our shop over the last eight years and consistantly see 140 to 160 degree F in the pan when the factory cooling system is working correctly. As an observation; the temperature between what you see on the engines temperature gauge and the fluid temperature inside the transmissions pan should always maintain a 30 to 50 degree F spread! Always!
the temperature you observe on the gauge is telling you
the fluid temperature after it's been cycled through
the radiator heat exchanger! This reading has nothing
to do with how hot the fluid got inside the torque converter.
If it reached 300 degrees F inside the torque converter
and you only see 150 degrees F at the sensor in the pan,
it doesn't mean the fluid wasn't overheated and degraded!
We do not know of a reasonable way to monitor the fluid
temperature inside the converter, so we always assume it
is very high during hard work situations. Locking
the converter during high heat production situations is
the only way to prevent the overheating from occuring in
the first place!
We also recommend a complete annual flush of the transmission fluid. We have a very simple method we teach our customers so they can change the whole systems volume not just the 4 1/2 to 5 quarts you can change by draining the pan.