Ford/Mazda vehicles equipped with the FNR5/5NR5 transmission may exhibit a complaint of harsh upshifts and/or downshifts, especially hot.
The cause may be that the bore where the pressure-regulator valve is situated is worn, causing high pressure or pressure instability.
To correct this condition, disassemble the valve body and inspect the bore where the pressure-regulator valve is situated (Figure 1). If the bore is worn, it will need to be reamed and a new pressure-regulator valve will need to be installed.
Note: Sonnax has a reamer and oversized pressure-regulator valve for the 4F27E that is exactly the same as for the FNR5. This is a very delicate process; the reamer must be used with the holding fixture, and the valve-body halves must be flat-sanded.
ATSG has provided information on the teardown and assembly of the FNR5’s main valve body in figures 1 and 2, as this information is not readily available and, most important, the solenoid names have changed.
Figures 3 and 4 show an exploded view of the secondary valve body.
Figure 5 is a schematic of the internal wiring harness with internal wire and connector colors. Figure 5 also illustrates the C134 connector, which has caused problems with trouble codes related to water intrusion; see special note.
Figure 6 shows a resistance-test chart for the solenoids on the main valve body.
Ford/Mazda vehicles equipped with the FNR5/5NR5 transmission may exhibit a complaint of a short bind-up during the 3-4 upshift.
The cause may be that during overhaul of the transmission, the clearance in the forward drum was adjusted too tight. Note in the application chart in Figure 7 that during the 3-4 upshift the forward clutch is turned off. If the clearance is too tight in this clutch there will be a brief bind-up.
The PCM is monitoring the opening and closing of the forward-clutch pressure switch (Figure 8) to help adjust the forward-clutch adaptives. It cannot change the adaptives enough for a forward-clutch pack that is stacked too tightly.
To correct this condition, refer to Figure 9 for a breakdown of the forward clutch and Figure 10 for a clearance check for the forward clutch, and be sure that the clearance is no less than 0.059 inch.
Note: Selective snap rings listed in the chart in Figure 10 for the 4F27E are the same for the FNR5.
July 2012 Issue
Volume 29, No. 7
- Ford/Mazda FNR5/5NR5: harsh shifts and/or downshifts
- Ford/Mazda FNR5/5NR5: short bind-up on 3-4 shift
