Shift Pointers NG I N Essential Reading T - Valve Body · PDF file6 T a i i Dige Shift Pointers Understanding the 5R55S/W Initial Engagements T he 5R55S/W transmission has been with

6 Transmission Digest

Shift Pointers

Understanding the 5R55S/W Initial Engagements

The 5R55S/W transmissionhas been with us for a littlemore than a decade. Its com-

mon complaints include harsh for-ward engagement; harsh reverseengagement; delayed, harsh initialengagements; flares on the 3-4shift; and bind-up on shifts.

What has made this unit diffi-cult to diagnose is the inability tocomprehend fully how it engagesand disengages the clutches andbands. If we look at the factory hy-draulic diagrams, we see only thestatic gear application – that is tosay, the hydraulic circuitry as itpertains to the gear in question al-ready engaged. What we don’t seeis the transition period, the stepsbetween the static applications.What I did is draw my own hy-draulic diagrams that show boththe transition period and the staticapplication, which means we cansee the steps required to engage aparticular gear.

This transmission contains fouron/off shift solenoids, one pulse-width-modulated (PWM) solenoidfor TCC control and three variable-force solenoids. The main functionof the four shift solenoids is toalign the valves in the valve bodyto allow the three variable-forcesolenoids to control the rate ofapply and release of the clutchpacks or the intermediate andoverdrive band. The PWM sole-noid controls the torque-converterclutch (TCC). With the transmis-sion in Park, Reverse, Neutral or

•Author: Jesse Zacarias

•Subject: Operation of pressure-control solenoids

•Unit: Ford 5R55S/W

TECH

NIC

ALTR

AIN

ING

Essential Reading

Rebuilder

Shop Owner

Center Manager

Diagnostician

R & R

1

continues page 8

Line pressureModulated line pressurePCA (VFS 1) pressurePCB (VFS 2) pressurePCC (VFS 3) pressure

SSA (SS1) pressureSSB (SS2) pressureSSC (SS3) pressureSSD (SS4) pressure

Reverse, Initial Engagement

To directclutch

To intermediateand VFS 2 modulator

control valves

From SSA (SS1) solenoid

Direct clutchcontrol valve

Reverse pressure

modulator valve

Reverse engagement control valve

From PCC (VFS 3) solenoid

From PCB (VFS 2) solenoid

Manual valve

Drive, the state of the four shift so-lenoids remains the same. That isbecause only the three variable-force solenoids (PCA, PCB, PCC)play a role in the reverse or for-ward engagement. Let’s look at thereverse and forward engagements.

When Reverse is selected(Figure 1), the transmission rangesensor sends a signal to the power-train control module (PCM) thatthe transmission was placed in re-

verse (Figure 2 on page 8). ThePCM then modulates variable-force solenoid 2 (PCB) with about0.5 amp, producing VFS 2 modu-lating pressure (blue in figure 1)that maintains the reverse-engage-ment control valve in the down po-sition. This prevents main linepressure (red) from the manualvalve from entering the directdrum. The on state of the SSA sole-

Copyright © 2012 Valve Body Pro


Shift Pointers

noid (yellow) keepsthe direct-clutch con-trol valve in the up po-sition, which allowsthe VFS 3 modulationpressure (orange) pro-duced by the PCC so-lenoid at thereverse-pressure mod-ulator valve to enterthe direct clutch. Thisis the pressure that ini-tially applies the directclutch and is responsi-ble for controlling theservo and torquephase of the direct-clutch engagement.

PCC pressure(green) is also directedto the bottom of the re-verse-engagementcontrol valve (Figure3). As the PCC amper-age is lowered by thePCM, PCC pressureincreases. As PCCpressure increases itovercomes PCB pressure (blue) atthe top of the reverse-engagementcontrol valve, moving it up andopening the passage for main linepressure to enter the direct-clutchdrum. This is the inertia phase ofthe direct-clutch engagement. Thecomplete engagement takes abouttwo seconds.

Now let’s look at the forwardengagement (Figure 4 on page 10).When Drive is selected, the trans-mission range sensor sends a sig-nal to the PCM that Drive wasselected. The PCM modulates vari-able-force solenoid 2 (PCB) withabout 0.5 amp, which producesVFS 2 pressure (blue). This pres-sure acts on top of the forward-en-gagement control valve, whichprevents main line pressure fromthe manual valve from entering theforward-clutch drum. The PCMstarts to lower the amperage of thePCA solenoid, which starts to in-crease VFS 1 pressure (orange) atthe VFS 1 modulation valve. ThisVFS 1 pressure is directed to the

continues page 10

3



Reverse, Complete Engagement

To directclutch

To intermediateand VFS 2 modulator

control valves

From SSA (SS1) solenoid

Direct clutchcontrol valve

Reverse pressure

modulator valve

Reverse engagement control valve

From PCC (VFS 3) solenoid

From PCB (VFS 2) solenoid

Manual valve


2


Shift Pointers

5

4 forward-clutch drumvia the forward-engage-ment control valve. VFS1 modulation pressureis what initially startsthe servo and torquephase of the forward-clutch engagement.

As VFS 1 modulatedpressure (orange) is en-tering the forward-clutch drum (Figure 5),it is also acting on thebottom of the forward-engagement controlvalve. As the amperageto the PCA solenoid islowered, VFS 1 modu-lated pressure increases.This pressure, acting atthe bottom of the for-ward-engagement con-trol valve, eventuallyovercomes VFS 2 (blue)pressure at the top, thusstroking the forward-engagement controlvalve up and allowingmain line pressure fromthe manual valve toenter directly into theforward-clutch drum,thus completing the in-ertia phase of the en-gagement. The completeengagement takes abouttwo seconds.

We hope this infor-mation will help youbetter diagnose thosecommon forward andreverse engagementproblems so prevalenton this unit and answerthe question someoneasked me not so longago: How can a badtransmission range sen-sor keep this transmis-sion from engagingforward or reverse?

Jesse Zacarias is the owner ofElec-Tran Diagnostics (www.elec-trandiagnostics.com) in Gilroy,Calif.

TD

1st Gear Initial Engagement, Drive Range

To overdrive servo

Release Apply

To intermediate servo

Release Apply



To forwarddrum

Todirectdrum

Direct clutch control valve

Reversepressuremodulator

valve

VFS 1 modulatorcontrol valve

Overdrive servocontrol valve

Forward engagement control valve

Intermediate servo select valve

Reverse servocontrol valve


Intermediatecontrol valve

From manual valve

From PCA (VFS 1)

From PCB (VFS 2)

From PCC (VFS 3)

From SSA (SS1)

From SSB (SS2)

From SSC (SS3)

From SSD (SS4)

1st Gear Complete Engagement, Drive Range

To overdrive servo

Release Apply

To intermediate servo

Release Apply



To forwarddrum

Todirectdrum

Direct clutch control valve

Reversepressuremodulator

valve


Overdrive servocontrol valve

Forward engagement control valve

Intermediate servo select valve

Reverse servocontrol valve


Intermediatecontrol valve

From manual valve

From PCA (VFS 1)

From PCB (VFS 2)

From PCC (VFS 3)

From SSA (SS1)

From SSB (SS2)

From SSC (SS3)

From SSD (SS4)



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Shift Pointers NG I N Essential Reading T - Valve Body · PDF file6 T a i i Dige Shift Pointers Understanding the 5R55S/W Initial Engagements T he 5R55S/W transmission has been with