The 4L60 series transmission is the most popular choice for high performance applications world wide. We at
Trutech Performance Transmission want to provide our customers with as much information as possible to make
their decision easier as to what performance parts are needed for their particular application. There is
always the question, "What friction and steel combination is best for my vehicle". In this guide we will
attempt to explain the difference in materials and design of friction apply components to make your decision
Depending on the application friction material and steel thickness can make a difference. First, we need to
know whether the clutch is holding (static) clutch or a shifting (dynamic) clutch. An example of a holding
or static clutch would be a forward or a reverse clutch. A shifting or dynamic clutch example is an intermediate
or 3-4 clutch. A holding clutch applies and transfers torque while the vehicle is at rest. So under normal
driving conditions they are not engaging or disengaging. The number of times the holding clutch applies is
significantly lower than if it were to be used in a shifting application. When a holding clutch is applied,
very little heat is generated in the clutch pack. A shifting or dynamic clutch needs to transfer torque by
coupling an inner hub to an outer hub, rotating at different speeds, during a gear ratio change or shift.
During a shift, shifting clutches transfer larger amounts of energy than a holding clutch. Therefore, a
greater amount of heat is generated during clutch apply, producing higher temperatures at the friction
and steel surface. The longer the slip, the higher the temperature, making engagement time a critical factor.
What type of friction material and steel thickness used in the clutch set up is important because it must
absorb and dissipate the generated heat to give long service life.
Frictions made with high energy papers possess very good thermal stability as power is absorbed by the clutch
pack. High energy frictions can be thought of as high heat frictions. Characteristics of high energy paper
frictions include the ability to slide more (lower friction) than that of high friction papers. Examples
of high friction papers are standard "tan", red performance and blue high performance frictions. High friction
papers typically have lower thermal stability, but greater power (torque) absorption. This makes high energy
materials an excellent choice for smooth, controlled or modulated shifts. A high horse-power application needs
a higher friction material with the ability to absorb higher torque over a shorter engagement or shift time.
Reducing shift time refers to the time required for the clutch or band to cause a component to stop motion. A
friction plate or material cannot change the signal to create a shift, however it does have an effect on the
duration of the shift. The rate of the shift apply is determined by the pressure and volume of the hydraulic
fluid in that apply circuit. At a fixed PSI, a high energy and a high friction material plate will take different
amounts of time to absorb torque and stop motion. Typically the high energy material will take more time. It can
be concluded, in stock to moderate torque applications a tan holding friction and a high energy shifting friction
is an excellent choice. In higher torque high performance applications a high friction red or blue material plate
is necessary to absorb higher torque.
As noted earlier, the clutch steels must have the ability to absorb and dissipate heat without warping, hot
spotting or coning. The ability to do so is related to the steel's mass or thickness. Increasing the number
of frictions also increases the clutches ability to absorb torque. This theory works great with holding
(static) clutches but not so well with shifting (dynamic) clutches. The reason being, to increase the number
of frictions the steels must be made thinner to get proper clearance. Thin plates cannot absorb or dissipate
heat as well as thicker steel plates. That is the reason specialty clutches that include thin steel plates,
so you can add more frictions, actually overheat and fail sooner than stock plates. There is a lot of engineering
needed to balance performance and durability.
In the 4L60 series transmissions the shifting frictions are the band and 3-4 clutch, the holding frictions are
forward, reverse input and low reverse clutches. The Trutech Level 1 Modules use the Borg Warner high energy
materials for the shifting components and Borg Warner tan/red frictions in the holding clutch applications.
The Trutech Level 1 Modules also includes a 3-4 clutch upgrade no other "rebuild kit" offers. This 3-4 clutch
upgrade is a high energy seven friction and 6 thick (.097") steel component kit. The apply and backing plate
necessary for proper clutch clearance are also included in this module. The Trutech Level 2 modules contain
the red performance plates from Alto (Red Eagle) or Raybestos (Stage 1) depending on customer preference. Both
of these kits have a seven friction and six thick (.106") steel set up for the 3-4 clutch. Our Level 3 Module
is Raybestos Blue Plate frictions with the same steel components as the Level 2 modules. The band included in
all Trutech Performance Overhaul Modules is the Alto carbon extra wide band. All our Performance Modules include
all necessary parts for proper 3-4 clutch clearance.
Trutech Performance Transmission offers it's customers a free technical assistance email hot line. All questions
will be answered within 24 hours.