A/T - E4N71B, L4N71B, 4N71B No 4th Gear
TECHNICAL BULLETIN # 113TRANSMISSION: E4N71B, L4N71B, 4N71B
SUBJECT: NO 4TH Gear
APPLICATION: Nissan, Mazda, Mitsubishi
DATE: May 92
A complaint of no 4th gear may be caused by several factors. Follow this step by step procedure to help isolate the problem.
[STEP 1]
Disconnect the wire (or wires) to the overdrive cancel solenoid. If you have no 4th gear with the wires disconnected go to Step 2. If you have 4th gear with the wires disconnected, a vehicle electronics problem is indicated. Since the electronics involved are vastly different for each vehicle, refer to the proper year service manual for the electronics trouble-shooting procedure. The O/D cancel solenoid is located on the O/D housing.
SERVICE INFORMATION: UNIT IDENTIFICATION
The 4N71B is a 4 speed non-lock-up transmission. It has an O/D cancel solenoid and kickdown solenoid. There were relatively few of these units produced.
The L4N71B is a 4 speed lock-up transmission. It has an O/D cancel solenoid and kickdown solenoid. It also has a tube on the left side which feeds governor pressure from the rear of the case to the bell housing, to control the lock-up valve.
The E4N71B is a 4 speed lock-up transmission. This unit has an O/D cancel solenoid, kickdown solenoid, and a lock-up solenoid. The E4N71B is the only model of the series with a solenoid on the bell housing.
[STEP 2]
Remove the inner O-ring from the O/D cancel solenoid and road test the vehicle. (Figure 2) If you still have no 4th go to step 3.
If you do have 4th the O/D cancel solenoid is defective. You will also notice that when the transmission shifts to 4th, the O/D cancel switch will not cancel O/D. Don't be alarmed by this as the solenoid is disabled for this test.
[STEP 3]
Check governor pressure. Governor pressure should be APPROXIMATELY the same as miles per hour (15mph = 15 PSI, 30 mph = 30 PSI etc...) The governor pressure tap is on the left rear of the case.
If governor pressure is substantially lower than miles per hour, check the governor and governor circuit. If governor pressure rise is OK go to step 4.
[STEP 4]
Remove the valve body and locate the 3-4 shift valve train. Make sure the 3-4 shift valve isn't stuck and make sure that the sleeve isn't installed backwards.
If the valve is stuck or the sleeve is backwards repair as required.
Note
Many manuals (factory and aftermarket) show the sleeve to be installed incorrectly. When the sleeve is installed backwards, governor pressure is blocked from reaching the 3-4 shift valve.
The above procedure will locate the most common problems. Other possible problems are:
1. Stuck overdrive cancel valve (located in drum support)
2. Defective Servo
3. Defective Band