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Technical Service Information
NISSAN RL4RO1A
FALLS OUT OF FOURTH GEAR
COMPLAINT: Vehicles equipped with the RL4RO1A transmission may exhibit a complaint of falling out
of 4th gear at "Highway" speeds, and will hold 4th gear at lower speeds.
CAUSE: The cause may be, a "Broken" or "Cracked" valve body bore plug at the end of the "Lock-Up
Control Valve Train", as shown in Figure 1. The reason is, when the vehicle speed and
governor pressure is high enough (Approx. 44-49 MPH), governor pressure moves the 4th
speed cut valve against spring pressure allowing 4th apply pressure to be fed to the lock-up
control valve, at the bore plug end, which strokes the lock-up control valve and applies the
converter clutch. When this action takes place, the broken bore plug can act as an exhaust
for 4th apply oil, causing the loss of 4th gear.
CORRECTION: Replace the broken or cracked bore plug with OEM part number 31845-41X07, and ensure
that it fits "snug" in the valve body bore. Refer to Figure 1.
SERVICE INFORMATION:
Valve Body Bore Plug ................................................................................. 31845-41X07
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AUTOMATIC TRANSMISSION SERVICE GROUP
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Technical Service Information
LOCK-UP CONTROL VALVE LOCATION
Special Note: The 4-3 MTV valve bore plug from a
THM 440-T4 valve body can also be used by opening
the center slot a small amount for the roll pin.
ROLL
PIN
BORE PLUG
31845-41X07
LOCK-UP CONTROL
VALVE AND SPRING
UPPER
VALVE BODY
Copyright © 2005 ATSG
Figure 1
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AUTOMATIC TRANSMISSION SERVICE GROUP
