It probably doesn't have a "filter," rather a metal screen which typically doesn't get replaced. Nissan's thinking is that if there is enough debris in the fluid to clog the screen, then there is something breaking down to the point where more than just a simple service will correct. If you want, drop the pan and spray it clean with some brake cleaner and clean out the inside of the pan and wipe off the metal shavings off of the magnet. I would recommend a new genuine Nissan gasket (P/N: 31377-41X25 ) and bolt set (P/N: 31397-41X04 ). Nissan recommends replacing the bolts as they are coated with a sealant. Part numbers apply to both 2WD and 4WD trannies for 1990.
If you still want to replace the filter, the part #'s are as follows:
2WD:
88-89: 31728-X8600
90-97: 31728-48X01 (4 cyl. engine)
90-95: 31728-80X03 (V6 engine)
4WD:
88-95: 31728-41X03
96-97: 31728-48X01
If you still want to replace the filter, the part #'s are as follows:
2WD:
88-89: 31728-X8600
90-97: 31728-48X01 (4 cyl. engine)
90-95: 31728-80X03 (V6 engine)
4WD:
88-95: 31728-41X03
96-97: 31728-48X01
