Stall Speed and Torque converter test for the 5R55N Automatic Transmission

Torque Converter Test procedure.

All stored Engine/Transmission DTC must have been worked through and corrected!

This procedure verifies that the torque converter clutch system and the torque converter are operating correctly.

Connect a tachometer to the engine.

Bring the engine to normal operating temperature by driving the vehicle at road speeds for approximately 15 minute in D position.

After normal operating temperature is reached, maintain a constant vehicle speed of about 50mph (80km/h) and tap brake pedal with the left foot.

The engine rpm should increase when brake pedal is tapped, and decrease about five seconds after pedal is released.

Stall Speed Test procedure.

All stored Engine/Transmission DTC must have been worked through and corrected!

A disconnected battery will not only delete engine idle values but also a part of the AT's learned adaptive strategy, run drive cycle tests!

ATF level ok?

This test checks operation of the following items, torque converter clutch, forward clutch, low one way clutch (OWC, Sprag) assembly, engine performance, overdrive one-way clutch (OWC, Sprag) assembly.




Always carry out the Line Pressure Test procedures prior to carrying out the Stall Speed Test. If line pressure is low at stall, do not carry out the Stall Speed Test or further transmission damage will occur.

Impulse sensor (failure, fault) have a large influence on the line pressure! Check thoroughly!

If there is a Line Pressure problem refer to Valve Body issues and testing procedures.


The Stall Speed test should be carried out with the engine and transmission at normal operating temperatures.

Connect tachometer to the engine or OBDII Scantool to the diagnostic connector.


After testing each of the following ranges D, 4, 3, 2 and R, move the transmission range selector to N (NEUTRAL) and run the engine at 1000rpm for about 15sec. to allow the torque converter to cool before testing the next range.


Do not maintain wide open throttle (WOT) in any range for more than five (5) seconds!


If the engine rpm recorded exceeds maximum specified rpm, release the accelerator pedal immediately! Clutch or band slippage is indicated.


Prolonged use of this procedure may set DTC PO712, P1783. After carrying out Stall Speed Test run OBD II Test and clear DTC's from memory.

Press accelerator pedal to floor (WOT, wide open throttle) in each range. Record rpm reached in each range.

Stall speeds, (which are the engine's RPM) should be as follows.

S-Type 3.0 (2533 to 3025)
S-Type 4.0 (2584 to 3009)

If stall speeds were too high, refer to the following Stall Speed Diagnosis down below.
If stall speeds were too low, first check the engine idle speed.
If engine idle is OK, remove torque converter, check one-way clutch for slippage. Replace the torque converter.

Stall Speed Diagnosis


Sprag = One-Way Clutch (OWC)

Set selector lever in D and 4, if Stall Speed "High" = Overdrive (Sprag) One-Way Clutch(a), Rear (Sprag) One-Way Clutch(b) (Replace transmission)

Set selector lever in D, 4 and 2, if Stall Speed "High" = Forward Clutch(c), Overdrive (Sprag) One-Way Clutch(a) (Replace transmission)

Set selector lever in D, if Stall Speed "High" = Forward Clutch(c), Overdrive (Sprag) One-Way Clutch(a) (Replace transmission)

Set selector lever in D,4,2 and R, if Stall Speed "High" = General Pressure Concerns, Forward Clutch(c), Overdrive (Sprag) One-Way Clutch(a), if Stall Speed "Low" = Torque Converter (Sprag) One-Way Clutch(d) or Engine Drive-ability Concerns

Set selector lever in R only, if Stall Speed "High" = High/Reverse and Direct/High Clutch(e) and Low and reverse Band/servo(f) (Replace transmission)

Set selector lever in 2 only, if Stall Speed "High" = Intermediate Band/Servo(g) (Replace transmission)

Check oil/pan for metal filings, particles, clutch/band fragments.

Known Issues:

ATF leakage radial seal(j) with a worn pump cover bushing(k).

A damaged intermediate sprag(h) will cause a bind in 3rd and 4th or no 3rd or 4th.

Check ball locations when servicing the valve body and install new check balls (2 check balls and one limit valve).

Solenoid body (5R55N 2000-2002) Art-nr.XW4Z-7G391-AE

Solenoid failure, the plastic block covering the solenoid circuit board rubs through solenoid wire strips. Multiple failure codes may set when this happens.

Valve Body Separator Plate Art-nr.XW4Z-7Z490-AB

Valves that commonly wear: PCA or VS1, PCB or VS2, and the Reverse Modulation Valve which controls High/direct clutch feed.

No Fourth Gear and No Fifth Gear:
The 4-3 pre-stroke intermediate band control valve spring may break. many springs were machined incorrectly. May set failure code PO795 (Pressure Control Solenoid C circuit failure or shorted)

No / or slow engagement concerns (Flow Control Valve(i)). The Flow Control Valve is used to help control the volume output of the pump.

Thermal Bypass Valve, this problem may cause an intermittent lockup failure code PO741

Metal in the Pan, broken Snap Ring, there may be no particular symptom other than metal the pan.

General Service Information

General Service Information

Rear axle

Rear sub-frame

Front axle

Lower ball-point joint, Shock absorber bushes, Stabilizer bar links + mounts

Brake disc and pads


Intake Manifold / Ignition Coils / Spark-plugs/ engine-block ventilation (elbow)


Starter system

Valve clearance, timing-chain, tensioner and glides:
With valve clearance in its tolerance, there was no need to take the camshafts down, so tensioners and co. have to wait, the good thing is the tensioner pumps up in 3-4 min. the rattle noise disappears.

Cruise control malfunction, emergency mode

Automatic Transmission 5R55N

Info, tips, Fail Safe Mode

Stall Speed Test procedure and diagnoses

Valve Body, known issues

Valve Body, Solenoid test procedures

Line Pressure Test

Self made press for pressing down clutch drum springs, checking clutch tolerance without a dial gauge


Air Conditioning

Miscellaneous repairs

Wind-shield-wiper mechanism:
Time on the lot took its toll, wind-shield-wiper shafts had seized, uninstalled the mechanism, freed the seized shafts through the use of a good rust loosener, heat, force.

Water in Spark-plug wells 3-2 cylinder:
After days of heavy rain the engine began to misfire with accounted trouble codes, spark-plug wells were wet, an ionized rusty red path on the ceramic insulator had developed which shorted the HV ignition spark.

Connected the radio controls to the multi-functional steering wheel using an analog digital converter.