Troubleshooting Automatic Transmission

Note: If transmission oil is black and smells burnt or there is an unusual large amount of metal burrs in oil pan, either repair or replace transmission.

Conditions and Correction

Condition: Transmission slips in all selector lever positions

Correction: 1, Check modulating pressure, adjusting if necessary. If not adjustable, check movement of modulating pressure control valve. Clean modulating pressure safety valve in shift valve housing upper section,

2. Check whether vacuum line from intake branch to vacuum box is plugged. If yes, replace.

3. Check operating pressure. If too low or not available:

a) Disassemble and clean shift valve housing, and service operating pressure control valve, b) Remove and inspect primary pump, replacing if necessary.

Condition: Transmission grabs or car vibrates when moving off

Correction: 1. Check modulating pressure, adjusting if necessary,

2. Pull off vacuum line from vacuum box, checking whether ATF or fuel escapes.

a) If ATF, replace vacuum box.

b) If fuel, check fuel injection system and repair.

Condition:

1st gear slips

Correction:

1. Check easy movement of control valve B 1, replacing shift valve housing if necessary.

2. Remove and install brake band piston B 1, check seal and replace if necessary.

3. Replace brake band B 1 and pressure part for B 1. Check easy movement of vent valves in support flange K 1, replacing support flange if necessary.

Condition:

Transmission slips during lst/2nd shift or in 2nd and 3rd gear

Correction:

1. Check modulating and operating pressures, adjusting if necessary.

2, Replace shift valve housing, also replacing sealing bushings on plug tubes,

3. Repair clutches K 1 and K 2 depending on findings. Visually inspect oil distribution sleeve, replacing if necessary.

Condition:

Transmission slips in 3rd gear

Correction:

1, Remove shift valve housing, check sealing bushings on plug tubes and replace same if necessary,

2. Repair clutch K 2 depending on findings. Visually inspect oil distribution sleeve, replacing if necessary.

Condition: Transmission slips when moving off in 1st and

2nd gear, or moving off not possible in forward gear. Reverse gear is still good

Brake band B 2 seriously worn or broken

Correction: Adjust brake band B 2 by installing a longer pressure pin. Replace brake band, if seriously worn or broken.

Condition: Transmission slips in all gears

No or insufficient modulating pressure

Correction: 1, Check modulating pressure, adjusting if possible.

2. Remove and service modulating pressure control valve.

3. Check and clean modulating pressure safety valve in shift valve housing upper section.

Condition: After installation, transmission has no power flow or fails after a brief time of operation

Torque converter not installed according to instructions. Drive dogs do not engage accurately in drive gear of primary pump.

Follow-up damage: Drive dogs of torque converter and primary pumps will be destroyed.

Correction: Install torque converter according to instructions.

Condition: No power flow a brief period (especially wh in all selector lever positions for immediately after starting engine en car had not been used for a while)

Torque converter drains partially via leaky or defective lubricating ring or valve in input shaft.

Correction: 1. Check lubricating ring on input shaft, replacing if necessary.

2, Checking ball valve in input shaft, replacing input shaft if necessary,

3. Check and clean lubricating pressure valve in shift valve housing.

Condition: No power flow in reverse gear

Correction: 1. Remove shift valve housing, check brake band B 3 and adjustment.

2. Remove brake band piston B 3 and check seal,

3. Replace one-way clutch in gear set.

Condition: Strong jolt when engaging selector lever in "D

Correction: 1. Adjust idle speed and CO level to specifications.

2. Check modulating and operating pressures, correcting modulating pressure if necessary.

3. Check vacuum line and connections for leaks.

4. Check whether pressure acceptance piston in rear transmission case moves easily and is installed correctly,

5. Check whether feed bore for pressure acceptance piston in rear transmission case is plugged,

Mote: If there is a hard engagement jolt when quickly shifting back and forth between "N" and "D" several times, there is no fault. The pressure pick-up requires a running time of approx, 2 seconds. If this time is given, the engagement jolt will also be correct.

Condition:

Strong jolts when changing gears

Correction:

J. Check modulating and operating pressures, adjusting modulating pressure if Accessary, if operating pressure is too high, replace shift valve housing.

2. Check vacuum line and connections for leaks.

3. Service control valve for converter adaptation.

Condition:

Strong jolt in downshift from 3rd to 2nd gear

Correction:

1. Replace seal on release end of B 2,

2. Replace brake band piston B 2,

Condition:

No upshifts

Correction:

1, Check governor pressure. If there is no governor pressure reading, continue with point 1, If governor pressure is correct, continue with point 2,

2, Disassemble, clean and service centrifugal governor.

3, Disassemble and clean shift valve housing, replacing if necessary (use new sealing bushings on plug tubes).

Condition:

No upshift on cold transmission, upshifts okay after short distance

Correction:

1, Replace shift valve housing (use. new sealing bushings on plug tubes).

Condition:

Upshifts only in upper speed range of gears

Correction:

1, Check and adjust control pressure cable.

2. Check governor pressure and replace centrifugal governor, if governor pressure is too low.

3. Service control pressure valve.

Condition:

Upshifts only in lower speed range of gears

Correction:

1. Tighten bolt for control pressure lever on transmission. Then check control pressure cable, adjusting if necessary.

2. Check full throttle, stop. Move accelerator pedal to kickdown and check whether throttle is against full throttle stop, adjusting if necessary.

3. Check governor pressure and replace centrifugal governor, if governor pressure is too high.

Condition:

No kickdown downshifts

Correction:

1. Check voltage at solenoid valve. If necessary, check wire connections against current flow diagram.

2. Remove solenoid valve. Connect removed valve to power supply and check function, replacing if necessary.

3. Tighten control pressure lever bolt on transmission. Then check control pressure, adjusting if necessary,

4. Check movement of kickdown control valve in shift valve housing upper section, replacing shift valve housing if necessary.

Condition: No brake shifts from 3rd to 2nd and 2nd to 1st

Correction: 1. Adjust control pressure cable.

2, Service brake shift piston, replacing shift valve housing if necessary.

Condition:

Automatic, unwanted downshifts outside of partial throttle downshift range, without operation of kickdown switch

Correction:

1, Remove kickdown solenoid valve.

Check O-ring on solenoid valve for damage.

2. Check whether kickdown switch sticks in pressed position, replacing if necessary,

3. Check whether solenoid valve sticks in open position, replacing solenoid valve if necessary.

4. Check movement of control pressure valve, cleaning shift valve housing and servicing valve if necessary, or replacing shift valve housing.

Condition:

Poor acceleration when moving off

Correction:

1. Check stall speed.

2. If stall speed drops below specified value by approx. 400 to 700 rpm, one-way clutch in converter is slipping. Replace torque converter.

Condition:

Transmission does not make upshifts

Correction:

7.. Check governor pressure and when not correct, clean and service centrifugal governor. If correct, continue with point 2.

2. Service master valve in shift valve housing, replacing shift valve housing if necessary,

Automatic

Transmission / Gears, Valve Body 928

Condition:

Parking lock does not engage

Correction:

Check adjustment of selector lever cable, correcting if necessary.

Condition:

Selector lever cannot be engaged in "R" and "P"

a) With engine running b) With engine stopped

Correction:

1, a) Disassemble, clean and service centrifugal governor.

2. b) Service blocking piston in rear transmission case.

Condition:

Engine cannot be started with selector lever in "P " or " N "

Correction:

1. Adjust selector lever cable and starter interlock switch.

2. Replace starter interlock and backup light switch.

Condition:

Invisible oil loss (leak cannot be seen on outside)

Diaphragm in vacuum box defective. ATF drawn in by engine via vacuum line.

Correction:

Replace vacuum box.

Condition:

Sudden thick smoke caused by defective vacuum box

Correction:

Replace vacuum box.

38 - 18 Troubleshooting Printed in Germany

Conditio il-

ATF lost between torque converter and primary pump

Correction:

1. Install and tighten drain plug for torque converter, using a new seal. Coat threads with Hyloma. If still leaking ATF, continue with points 2 and 3.

2. Replace radial seal and O-ring of primary pump, checking O-ring groove in primary pump for porous spots. Replace primary pump, if necessary.

3, Apply a good coat of Hyloma to threads of bottom mounting bolts,

Condition: Oil leak behind starter interlock and backup light switch

Correction: Replace O-ring on pressure part B 2.

Condition: 2nd gear loud

Correction: Replace rear planet gear set.

Condition: Whining noise only when changing gears with full load

Correction: Replace oil filter.

Condition: Whining noise, which increases in loudness as engine speed rises

Correction: Check primary pump, replacing if necessary.

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