Online Manual Jeep > Jeep Cherokee > Jeep Cherokee (XJ) > 1984 - 1991 > AW-4 > part 2

NOMENCLATURE

FUNCTION

Overdrive Direct Clutch

Connects overdrive sun gear and overdrive carrier

Overdrive Brake

Prevents overdrive sun gear from turning either clockwise or counterclockwise

Overdrive One-Way Clutch

When transmission is driven by engine, connects overdrive sun gear and overdrive earner

Forward Clutch

Connects input shaft and front ring gear

Direct Clutch

Connects input shaft and front and rear sun gear

Second Coast Brake

Prevents front and rear sun gear from turning either clockwise or counterclockwise

Second Broke

Prevents outer race of No. 1 one-way clutch from turning either clockwise or counterclockwise, thus preventing front and rear sun gear from turning counterclockwise

First/Reverse Brake

Prevents rear planetary carrier from turning either clockwise or counterclockwise

One-Way Clutch No. 1

When second brake is operating, prevents front and rear sun gear from turning counterclockwise

One-Way Clutch No. 2

Prevents rear planetary carrier from turning counterclockwise

Fig. 7 Component Function Chart



•=Applied

Fig. 8 Component Application Chart


HYDRAULIC SYSTEM

The basic hydraulic system consists of the oil pump, valve body and solenoids and four hydraulic accumu­lators. The oil pump provides the necessary system lu­brication and operating pressure.

The valve body controls application of the clutches, brakes, second coast band and the torque converter lockup clutch. The valve body solenoids control se­quencing of the 1-2, 2-3 and 3-4 shift valves within the valve body. The solenoids are activated by signals from the TCU.

The accumulators are used in the clutch and brake feed circuits to control initial apply pressure. Spring loaded accumulator pistons modulate the initial surge of apply pressure for smooth engagement.

Oil Pump

A gear-type oil pump is used in all AW-4 transmis­sions. The pump gears are mounted in the oil pump body. The drive gear is operated by the torque converter hub. Drive tangs on the hub engage in drive slots in the drive gear.

Valve Body Components

Transmission operating pressure is supplied to the clutch and brake apply circuits through the valve body. The valve body consists of an upper body, lower body, separator plate and upper and lower gaskets (Fig. 9). The various spool valves, sleeves, plugs and springs are located within the two body sections.

The manual valve, 1-2 shift valve, primary regulator valve, accumulator control valve, check balls, solenoids and oil strainers are located in the lower body section (Fig. 10). The remaining control and shift valves plus

check balls and one additional oil strainer are located in the upper body section (Fig. 11).

Manual Valve

The manual valve is operated by the gearshift link­age. The valve diverts fluid to the apply circuits ac­cording to shift lever position.

Primary Regulator Valve

The primary regulator valve (Fig. 13) modulates line pressure to the clutches and brakes according to engine load. The valve is actuated by throttle valve pressure.


DIAGNOSIS INFORMATION

GENERAL DIAGNOSIS INFORMATION

The TCU used with the AW-4 transmission has a self-diagnostic program. The program is compatible with the DRB II tester.

The AW-4 is an electronically controlled transmis­sion. Shift points and sequence in the forward gear ranges are controlled by the TCU. Before attempting repair, it will be necessary to determine if a malfunction is electrical or mechanical.

The DRB II tester will identify faults in the electrical control system. The road test, pressure test, stall test and time lag test plus the general diagnosis charts will help locate faults in the mechanical running gear.

All AW-4 diagnosis should begin with the Prelimi­nary Check Procedure. The procedure is designed to help identify the type of problem (mechanical/electri­cal) that has occurred. The first step of the procedure is Initial Inspection and Adjustment which is detailed in this section.

INITIAL INSPECTION AND ADJUSTMENT

  1. Check and adjust shift linkage.

  2. Verify line pressure cable operation. Repair or
    replace cable if it binds or is damaged.

  3. Check engine throttle operation. Have helper
    press accelerator to floor and observe injector throttle
    plate movement. Adjust linkage if throttle plate does
    not reach wide open position.

  4. Check and adjust line pressure cable if necessary.

  5. Check transmission fluid level when fluid is at
    normal operating temperature. Start engine. Shift
    transmission through all gear ranges then back to Neu­
    tral. Correct level is to Full or Add mark on dipstick
    with engine at curb idle speed.

  6. Check and adjust neutral switch if necessary.

  7. Check TPS adjustment and operation. Adjust the
    sensor if necessary.

MANUAL SHIFTING TEST

  1. This test determines if the problem is related to a
    mechanical or electrical component.

  2. Stop engine and disconnect TCU or TCU fuse.

  3. Road test vehicle. Shift transmission into each
    gear range. Transmission should operate as follows:


  1. lock in Park

  2. back up in Reverse


  1. not move in Neutral

  2. provide first gear only with shift lever in 1-2 position

  3. operate in third gear only with shift lever in 3 posi­
    tion

  4. operate in overdrive fourth gear in D position

(4) If transmission operates as described, proceed to
next step. However, if forward gear ranges were diffi­
cult to distinguish (all feel the same), or vehicle would
not back up, refer to diagnosis charts. Do not perform
stall or time lag tests.

CAUTION: Do not overspeed the engine during the next test step. Ease off the throttle and allow the ve­hicle to slow before downshifting.

  1. Continue road test. Manually downshift transmis­
    sion from D to 3, and from 3 to 1-2 position. Then man­
    ually upshift transmission through forward ranges
    again.

  2. If transmission operation is OK, perform stall,
    time lag and pressure tests. If transmission shifting
    problem is encountered, refer to diagnosis charts.

  3. If a problem still exists, continue testing with DRB
    Ïtester.

HYDRAULIC PRESSURE TEST

Pressure Test Procedure

  1. Connect pressure test gauge to test port on pas­
    senger side of transmission. Use adapter 7554 to con­
    nect gauge. Be sure test gauge capacity is a minimum
    of 300 psi (210OkPa>.

  2. Bring transmission fluid to normal operating tem­
    perature.

  3. Apply parking brakes and block wheels.
    WARNING: DO NOT ALLOW ANYONE TO STAND AT
    THE FRONT OR REAR OF THE VEHICLE WHILE PER­
    FORMING THE FOLLOWING STEPS IN THE PRES­
    SURE TEST.

  4. Check and adjust engine curb idle speed.

  5. Apply service brakes.

  6. Shift transmission into D range and note line pres­
    sure with engine at curb idle speed. Pressure should be
    53-to-61 psi (363-to-422 kPa).

  7. Press accelerator to wide open throttle position
    and note line pressure. Pressure should be 161-to-196
    psi (1108-to-1353 kPa).

CAUTION: Do not maintain wide open throttle (or more than three or four seconds at a time.

  1. Shift transmission into Reverse and note line pres­
    sure with engine at curb idle speed. Pressure should be
    -Þ-87 psi (500-to-598 kPa).

  2. Press accelerator to wide open throttle position
    and note line pressure in Reverse. Pressure should be
    223-to-273 psi (154O-to-1883 kPa).

CAUTION: Do not maintain wide open throttle for more than three or four seconds at a time.

(10) If line pressure is not within specifications, adjust
line pressure cable arid repeat pressure test.

Pressure Test Analysis

If pressures in D and Reverse are higher than spec­ified, check for the following:

• line pressure cable loose, worn, binding or out of adjustment

• throttle valve, downshift plug, throttle cam sticking,
worn or damaged

• primary regulator valve sticking, worn, or damaged
If pressures in D and Reverse are lower than specified,

check for the following:

  1. line pressure cable loose, worn, binding or out of
    adjustment

  2. throttle valve, downshift plug, throttle cam sticking,
    worn or damaged

  3. primary regulator valve sticking, worn, or damaged

  4. oil pump gears or housing worn or damaged

  5. overdrive clutch worn or damaged

If pressures are low in D range only, check for the following:

  1. forward clutch worn or damaged

  2. fluid leakage in D range circuit (component seal and
    O-rings)




If pressures are low in Reverse only, check for the following:

  1. shift linkage (and manual valve) out of adjustment

  2. fluid leakage in Reverse circuit (component seal and
    O-ringa)

  3. direct clutch worn or damaged

  4. first/reverse brake worn or damaged

STALL TEST

  1. The stall test checks holding ability of the trans­
    mission clutches and brakes and the torque converter
    stator clutch.

  2. Bring transmission fluid to normal (hot) operating
    temperature.

  3. Connect tachometer to engine. Position tachome­
    ter so itcan be viewed from drivers seat.

  4. Apply parking brakes and block wheels.

  5. Apply and bold service brakes.

  6. On 4WD models, shift transfer case into two-wheel
    high position.

  7. Start engine.

WARNING: DO NOT ALLOW ANYONE TO STAND AT THE FRONT OR REAR OF THE VEHICLE DURING THE TEST.

(8) Shift transmission into D range.

(9) Press accelerator to wide open throttle position
and note maximum engine rpm. Stall speed should be
2100-to-2400 rpm in D range.

CAUTION: Do not maintain wide open throttle tor more than four or five seconds at a time.

  1. Release throttle and shift transmission into Neu­
    tral. Allow transmission fluid to cool for 15-20 seconds.

  2. Shift transmission into Reverse.

  3. Press accelerator down to wide open throttle po­
    sition and note maximum engine rpm. Stall speed

should be 2100-to-2400 rpm in Reverse.

Stall Speed Test Analysis

If engine rpm is lower than specified in D and Reverse, check for the following:

  1. engine output/performance insufficient

  2. stator clutch in torque converter not holding if engine
    speed was 1500 rpm or less.

If stall speed in D range is higher than specified, check for the following:

  1. line pressure low

  2. forward clutch slipping

  3. No. 2 one-way clutch not holding

  4. overdrive one-way clutch not holding

If stall speed in Reverse was higher than specified, check for the following:

  1. line pressure low

  2. direct clutch slipping

  3. first/ reverse brake slipping

  4. overdrive one-way clutch not holding

If stall speeds were higher than specified in both D and Reverse, check for the following:

  1. low fluid level

  2. line pressure low

  3. overdrive one-way clutch not holding

TIME LAG TEST

This test checks general condition of the overdrive clutch, forward clutch, rear clutch and first/reverse brake. Condition is indicated by the amount of time required for clutch/brake engagement with the engine at curb idle speed. Engagement time is measured for D and Reverse positions. A stop watch is recommended for test accuracy.

Test Procedure

  1. Check and adjust transmission fluid level if nec­
    essary.

  2. Bring transmission to normal (hot) operating tem-
    pertue.

  3. Apply parking brakes.

  4. Turn off air conditioning unit.

  5. On 4WD models, shift transfer case into two-wheel
    high.

  6. Start engine and check curb idle speed. Adjust
    speed if necessary. Curb idle must be correct to ensure
    accurate test results.


  1. Shift transmission into Neutral and set stop
    watch.

  2. During following test steps, start stop watch as
    soon as shift lever reaches D and Reverse detents.

  3. Shift transmission into D range and record time it
    takes for engagement. Repeat test two more times.


  1. Reset stop watch and shift transmission back to
    Neutral.

  2. Shift transmission into Reverse and record time
    it takes for engagement. Repeat test two more times.

(12) Engagement time in D range should be a max­imum of 1.2 seconds. Engagement time for Reverse should be a maximum of 1.5 seconds.

Time Lag Test Analysis

If engagement time is longer than specified for D range, check for the following:

  1. shift linkage misadjusted

  2. line pressure low


  1. forward clutch worn

  2. overdrive clutch worn or damaged

If engagement time is longer than specified for Re­ verse, check for the following:

  1. shift linkage misadjusted

  2. line pressure low

  3. direct clutch worn

  4. first/reverse brake worn

  5. overdrive clutch worn or damaged

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