Technical Bulletin #1597
Transmission: FNR5
Subject: P0735 Gear Ratio Error - 5th Gear Slipping,
P0778 PCS B Stuck Off
Application: Ford, Mazda
Issue Date: March, 2014
FNR5
P0735 Gear Ratio Error, 5th Gear Slipping, P0778
Diagnosing a Ford FNR5/Mazda FS5A-EL with a code P0735, 5th gear slipping or P0778 pressure con-
trol solenoid B stuck off can be challenging. Many attempts have been made to correct this code by
installing a new PCS B solenoid or by installing a new secondary valve body with little to no success.
These codes generally set when the transmission fluid temp is hot. Always address the P0735 code
last if other shift complaints or solenoid performance codes are present.
Secondary Valve Body
Shift Solenoid F
Pressure Control Solenoid B
Copyright © 2014 ATRA All Rights Reserved MP • Page 1 of 3
FNR5 #1597
P0735 Gear Ratio Error, 5th Gear Slipping, P0778
The purpose of the secondary valve body and solenoids is to control the application of the reduction
brake and direct/5th clutch in the reduction unit. The reduction brake is on in 1st thru 4th gear. In 5th
gear the reduction brake releases and the direct/5th clutch comes on. If the direct/5th clutch slips
while in 5th gear the P0735-P0778 will set.
FNR5/5NR5 Transaxle Component Application Chart
Reduction
Forward 2-4 Brake 3rd & 4th Reverse Low/Rev Low One- Direct Gear
Range Brake &
Clutch Band Clutch Clutch Clutch Way Clutch Clutch 5th Ratio
One-Way Clutch
Park On
Reverse On On On 3.40
Neutral On
Drive - 1st On Hold On 3.61
Drive - 2nd On On On 1.92
Drive -3rd On On On 1.28
Drive - 4th On On On 0.93
Drive - 5th On On On 0.69
Manual - 2nd On On On 1.92
Manual - 1st On On On 3.61
NOTE: Failsafe on this unit is 3rd gear in all forward ranges.
The One-Way Clutch, which is locked when the Reduction Brake is ON.
As stated at the beginning, most attemps to address the P0735 code by changing the pressure control
solenoid B, secondary valve body or shift solenoid E will often fail. Here’s why: The secondary valve
body is fed line pressure from the main valve body.
If the line pressure output from the main valve body is below specifications, then the pressure input
to the secondary valve body will be low causing the 5th clutch to silp.
Often the cause of the P0735 is main valve body bore wear concerns. The valve bodies are problemat-
ic with this transmission and the 4F27E. EPC solenoid problems can contribute to this as well.
If the transmission has other shift complaints such as late or harsh 1-2, no movement in manual low
or shift solenoid DTC’s address these problems first as these complaints are also related to valve body
bore wear.
MP • Page 2 of 3 Copyright © 2014 ATRA All Rights Reserved
#1597 FNR5
P0735 Gear Ratio Error, 5th Gear Slipping, P0778
All of the valve bores shown here require careful inspection during repairs along with the servo pin
bore.
Solenoid Regulator Valve
Pressure Regulator
Torque Converter Limit Valve
Copyright © 2014 ATRA All Rights Reserved MP • Page 3 of 3
