A/T - Line Pressure Drops to Nearly Zero
90nissan01Classification: AT90-001 Section: Auto. Trans.
Reference: TECHNICAL BULLETIN NTB90-009
Models:
1989-90 Maxima
Date:
February 1, 1990
IMPROPER OPERATION OF AUTOMATIC TRANSMISSION
APPLIED VEHICLES:
JN1HJ01P*KT282647 - 299351. JN1HJ01P*LT350101 - 366718.
SERVICE INFORMATION:
Some 1989-90 Maximas, equipped with automatic transmissions, may experience a drop in hydraulic control pressure after the transmission has reached a warm temperature. This pressure drop is caused by foreign material clogging the transmission's filter screen. It is extremely important for the technician to thoroughly inspect the control valve body and other internal components to ensure that these elements have not been contaminated by debris. On affected vehicles, the line pressure drops to nearly "0," rendering the vehicle inoperative. However, the incident vehicle's transmission may operate properly when cold.
REPAIR PROCEDURE:
Special Disassembly Instructions
1. Remove the automatic transaxle assembly from the vehicle.
2. Disassemble the automatic transaxle. Additional procedural information can be found in the 1989 Maxima Service Manual, pages AT-89 - 94 or in the 1990 Maxima Service Manual, pages AT-95 - 100.
NOTE: It is very important to observe the following special areas and precautions;
Figure 1:
Clean and inspect the transmission case, especially in the area identified in Figure 1 and be careful to remove any signs of weld splatter or other foreign debris.
Figure 2:
Figure 3:
Clean and examine those transmission parts which have been CIRCLED in Figures 2 and 3. Replace those parts, as necessary.
The Control Valve Assembly should be completely disassembled and cleaned to remove all foreign matter. This will prevent the control valves from sticking.
Figure 4:
Special Re-Assembly Instructions
1. Replace torque converter assembly.
2. Replace the oil strainer and its associated O-ring (Figure 4).
3. Complete transmission reassembly using procedural information found in the 1989 Maxima Service Manual, pages AT-125 - 143 or in the 1990 Maxima Service Manual, pages AT-123 - 143.
4. As a supplementary precaution, to ensure that all debris has been removed from the transaxle, perform the following:
^ Operate the vehicle until the powertrain is sufficiently warm.
^ Drain the transmission oil and replace it with Genuine Nissan ATF, P/N 999MP-A7004QT.
^ Drive the vehicle to verify that all transmission operational problems have been resolved.