Hummer H1 (2006+). Manual - part 192

5-8

Transmission/Transfer Case

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SHIFT SOLENOIDS

The 1000 Series control valve body contains both normally closed (N/C) and normally open (N/O) solenoids. A N/C solenoid re-
mains closed until a signal from the TCM energizes the solenoid. A N/O solenoid remains open until the TCM energizes the sole-
noid. When a solenoid valve is in the closed position, the valve blocks the flow. When a solenoid valve is in the open position, flow
is permitted through the valve. The torque converter clutch pulse width modulated (TCC PWM) solenoid and the shift solenoids C,
D, and E are N/C. Both solenoid types have an orifice, electrical windings, an iron core, and a steel check ball.

The solenoids used in the 1000 Series differ in their ability to control flow or fluid pressure. The solenoids may operate in the open
or closed state with no modulation capability (C, D, and E solenoids), intermediate flow and resultant pressure based on duty cycle
(F solenoid) or produce pressure proportional to current (A and B solenoids).

Shift solenoids C, D, and E provide the necessary logic to distribute fluid to the correct clutches. The shift solenoids provide either
full control main pressure or exhaust to the head of each of the corresponding shift valves C, D, and E. Since the valve states,
stroked or unstroked, are critical to providing the correct transmission range, each shift valve has a pressure switch, located in the
pressure switch manifold, which provides feedback to the computer as to the position of the valve.

The modulated main pressure solenoid is a normally closed solenoid used to modulate the transmission main pressure. Under spe-
cific conditions, such as a low throttle setting, low engine torque, low engine speed, and low transmission output speeds, the trans-
mission control module (TCM) commands the solenoid on. When the solenoid is applied, fluid is routed to the main pressure
regulator valve; this in turn reduces the main pressure schedule and improves the volume of oil through the overage circuit. By
modulating main pressure, the cooler flow at idle can be increased allowing improved cooling and reducing transmission pump
noise.

Trim solenoids A and B are used to control on-coming, off-going and holding pressure to the five clutches. These solenoids are re-
ferred to as PPC solenoids, since the output hydraulic pressure supplied by these solenoids is proportional to the controlled current
command.

N/C = Normally Closed

N/O = Normally Open

* C pressure switch reverts to the Closed/ON state with throttle applied in Reverse.

The Allison 1000 series transmission consists of (5) clutches labeled C1 to C5. A combination of (2) clutches is required to be en-
gaged to attain a torque path from the input to the output of the transmission. The following chart indicates the clutch combinations
for each gear range.

Range

Pressure

Switch C

N/O

Pressure

Switch C

N/O

Pressure

Switch D

N/O

Pressure

Switch D

N/O

Pressure

Switch E

N/O

Pressure

Switch E

N/O

Pressure

Switch R

N/C

Pressure

Switch R

N/C

Switch

Status

Scan Tool

Status

Switch

Status

Scan Tool

Status

Switch

Status

Scan Tool

Status

Switch

Status

Scan Tool

Status

Open

OFF*

Closed

Open

OFF

Open

OFF

Closed

Open

OFF

Open

OFF

Open

OFF

Open

OFF

Open

OFF

Open

OFF

Closed

Open

OFF

Open

OFF

Open

OFF

Closed

Open

OFF

Closed

Open

OFF

Open

OFF

Open

OFF

Closed

Open

OFF

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Transmission/Transfer Case 5-9

5745804

This transmission utilizes clutch-to-clutch shift control to achieve ranges. In every case, except shifts to or from the neutral posi-
tion, one clutch is exhausted and another is applied to make a range shift. The hand off between exhausting and applying clutches
is very precisely controlled by use of two PPC (Pressure Proportional to Current) solenoids. These solenoids are “A” and “B” in the
transmission and are referred to as “trim” solenoids. For example, to make a 1-2 shift, A solenoid is used to trim pressure off C5
clutch and B solenoid is used to trim pressure on C4 clutch. The transmission control module (TCM) modulates the current to both
A & B solenoids, which translates to a proportional level of pressure to the clutch. In order to make a shift, the TCM uses software
and calibration settings of several program parameters to determine the level of current sent to the respective trim solenoids. These
parameters are referred to as “adaptive values”. With a new transmission and TCM calibration, the adaptive values are set to base
calibration level. The transmission uses the calibration to perform the first of each type of shift. However, once it has performed a
shift, the TCM evaluates the actual shift and compares it to an ideal shift in the TCM’s memory. Based on that comparison, the
TCM changes the settings of the adaptive values to a level that it believes will result in a shift closer to the idle shift the next time
it makes that type of shift. This is referred to as “adaptive shifting”. When the transmission /TCM calibration is new, the TCM is in
fast adaptive mode. In other words, the TCM is allowed to make relatively large changes in the adaptive values after each shift.
Once the TCM determines that a given shift is close to its ideal level, it switches to slow adaptive mode. In slow adaptive mode, the
TCM is still evaluating shifts and changing adaptive values, but is only allowed to do so in small increments. When a shift switches
from fast to slow adaptive mode, it is described as “converged”. The TCM is programed to try to switch from fast to slow adaptive
mode in as many as 15 to 20 shifts. It is important to understand that there are many different distinct shifts recognized by the
TCM, and each of these shifts has its own adaptive values. For example, there are up shifts and down shifts to and from each range,
as well as unique adaptive values for several different throttle regions for each up shift and down shift. The point is, it may take a
significant amount of time before most of the shifts converge from fast to slow adaptive, and it is not unusual to experience some-
what harsh or unpleasant shift quality until these shifts are adapted.

Torque converter clutch (TCC) engagement is accomplished by a separate pulse-width modulated (PWM) solenoid (F) in the trans-
mission. There are adaptive values for this as well, and it will also require some driving for TCC engagement to converge.

TRANSMISSION ABUSE PROTECTION MODES

Transmission abuse protection modes are encountered when one of the following type of maneuvers is performed.

• Shifting from Neutral to Drive/Reverse when the engine RPM is greater than 1400 RPM.

• Shifting from Drive to Reverse when the accelerator pedal position (APP) is greater then 25%, such as rocking the vehicle

when stuck and attempting to free the vehicle.

• When the transmission output speed is greater than 300 RPM while attempting a change in direction, such as Reverse to

Drive, Drive to Reverse or Neutral to Reverse.

When the TCM encounters any one of the above conditions, the TCM will flash the check transmission malfunction indicator light
and default to neutral. When the TCM sees that the RPM has dropped to a safe level it will then engage the selected range.

Gear Range

TCC

Park/Neutral

Reverse

First

Second

Third

Fourth

Fifth

5-10

Transmission/Transfer Case

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FAST LEARN PROCEDURE

In general, the fast learn procedure for the allison transmission runs a series of tests to allow the transmission control module
(TCM) to “learn” individual clutch characteristics. Once the clutch data is learned, Fast Learn translates it to the adaptive data
cells, which the TCM uses for clutch control during range shifts. Fast Learn is used at the assembly plant and allows the vehicle to
be driven off the line in a near-fully-adapted state so as to minimize any customer shift complaints. The Scan Tool version of Fast
Learn is intended to provide the same benefit following transmission repair or replacement at the dealership.

Fast Learn must be used when one of the following repairs is made to the vehicle.

• Transmission replacement or internal service/overhaul.

• Valve Body repair or replacement, including replacement of the A or B trim solenoids.

• Transmission Control Module (TCM).

• TCM software/calibration update.

• Any service in response to a shift quality complaint.

The Scan Tool is used to start Fast Learn by selecting the following functions:

• Special Functions.

• Transmission Output Controls.

• Fast Learn.

NOTE: When performing Fast Learn the following conditions must be met:

• Block the drive wheels.

• Apply the park brake.

• Apply the service brake during Drive and Reverse mode.

• 0% throttle, engine at idle RPM.

• Transmission temperature must be between 40 and 100 degrees C.

• The transfer case must be in high (H) range.

Description

Four steps are required to successfully complete the Fast Learn procedure.

Park Mode.

Drive Mode.

Reverse Mode.

C2 Learn Mode.

Park mode

While the transmission is in Park with the engine idling, Fast Learn will cycle through a series of tests where C3 and C4 clutches
are repeatedly applied to learn their clutch characteristics. During the C3 and C4 clutch apply/release procedure, Fast Learn is able
to characterize the A and B solenoid pressure corresponding to clutch return springs, and also is able to learn the volumes for C3
and C4 clutch packs. In addition, C5 clutch is repeatedly applied and released in Park to purge out air for later learning of its clutch
volume.

Drive Mode

WARNING: While in Drive, if the Scan Tool loses communication, or becomes disconnected, the vehicle may re-
main in Drive and could move forward if the wheels have not been securely blocked.

Once all the Park test data has converged, the Scan Tool instructs the driver to select Drive. Once Drive is selected, the TCM en-
gages C1 clutch to obtain Drive and learn C1 clutch volume. The TCM repeats this test until the volume learned for C1 clutch has
converged.

6-1-05

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Transmission/Transfer Case 5-11

5745804

Reverse Mode

WARNING: While in Reverse, if the Scan Tool loses communication, or becomes disconnected, the vehicle may re-
main in Reverse and could move backward if the wheels have not been securely blocked.

Next the Scan Tool instructs the driver to select Reverse. Once Reverse is selected, the TCM engages C5 clutch to obtain Reverse
and learn C5 clutch volume. The TCM repeats this test until the volume learned for C5 clutch has converged.

After learning C1 and C5 clutch volume, Fast Learn updates the adaptive volume data for all shifts with either C1 or C5 on-coming
clutch. This completes the “stationary modes” of Fast Learn.

NOTE: All shifts will be left in “fast” adaptive mode at this point.

C2 Learn Mode

Following the Reverse Mode step, the Scan Tool exits Fast Learn and the only adaptive cells that remain to be learned are the adap-
tive volume data for C2 clutch. The vehicle must be driven in order to make at least 3-4 upshifts on the same ignition cycle and at
steady throttle position. This data is learned by the TCM intentionally overfilling C2 clutch. Once this overfill is corrected the C2
clutch volume is learned and all special Fast Learn actions are completely disabled.

NOTE: The technician should verify that the transmission shift quality is acceptable before releasing the vehicle to the customer.

RECOMMENDED FLUID

The recommended and preferred fluid for Allison transmissions is Dexron III.

In cases where Dexron III is not readily available, Dexron IIE can be used to top off the fluid level. It is not, however, recom-
mended for use as the primary fluid for a fluid change.

Fluid Capacity

The fluid capacity of the Allison transmission used in the HUMMER H1 vehicles is:

• Transmission refill capacity (after filter change) is approximately 8.5 qt. (8.0 L).

• Dry fill capacity (after overhaul) is approximately 11.5 qts (11.0 L)

• Cooler and line capacity is approximately 1.0 qts (.94 L)

NOTE: Always fill the transmission using the dipstick level as a guide. The residual fluid left in the transmission during service
could result in an overfilled condition.

Fluid Level and Condition

The transmission fluid level and the condition are important for proper operation. An incorrect fluid level can lead to shift prob-
lems, fluid breakdown, and accelerated wear.

Check the fluid level and the condition during the preliminary inspection procedure. This is important, as a low fluid level, or over-
fill condition can lead to slip and flare, overheating, burned fluid, slow engagement, converter shudder, and no fourth gear upshift.

An overfill condition allows the gear train to churn the fluid into foam. This action aerates the fluid causing slip, overheating, oxi-
dation, and overflow from the vent. A low level allows the pump to take in air along with the fluid. Air in the fluid will cause the
pressures to be low and develop slower than normal shifts.

TRANSMISSION FLUID CHECKING PROCEDURE (COLD)

The purpose of checking the fluid cold is to determine if the transmission has enough fluid to be operated safely until the check can
be performed.

NOTE: The fluid level rises as fluid temperature increases. DO NOT fill above the “COLD” band if the transmission fluid is be-
low normal operating temperatures.

Bring the vehicle to a complete stop on a level surface using the service brakes.

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